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Fire history and climate-fire relations in Jasper National Park, Alberta, Canada Chavardès, Raphaël Daniel 2014

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FIRE HISTORY AND CLIMATE-FIRE RELATIONS IN JASPER NATIONAL PARK, ABERTA, CANADA  by Raphaël Daniel Chavardès  B.A., The University of British Columbia, 2011  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Forestry)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  April 2014  © Raphaël Daniel Chavardès, 2014 ii  Abstract In mixed-conifer forests of western North America, fire ecologists and managers are increasingly recognizing the prevalence and importance of mixed-severity fire regimes. However, these fire regimes remain poorly understood compared to those of high- and low-severity. To enhance understanding of fire regimes in the montane forest of Jasper National Park (JNP), I reconstructed fire history and assessed forest composition, age and size structure at 29 sites (Chapter 2). Historic fires were of mixed severity through time at 18 sites, whereas the remaining 11 sites had evidence of high-severity fires only. At the site level, mean importance values of canopy trees were more even among coniferous species and greater for Pseudotsuga menziesii at mixed-severity sites. The greater numbers of veteran trees and discontinuous age structures were also significant indicators of mixed-severity fire histories.  In a second study, I crossdated tree ages and fire-scar dates for 172 sites and tested whether historic fire occurrence depended on inter-annual to multi-decadal variation in climate (Chapter 3). Eighteen fires between 1646 and 1915 burned during drought years, with a weak association to El Niño phases and the negative phase of the Pacific Decadal Oscillation. Fire frequency varied through time, consistent with climate drivers and changes in land use at continental to inter-hemispheric scales. No fire scars formed since 1915, although potential recorder trees were present at all sites and climate was conducive to fire over multiple years to decades. Thus, the absence of fires during the last century can largely be attributed to active fire suppression. Improved understanding of the drivers of the historic mixed-severity fire regime enhances scientifically-based restoration, conservation, forest and wildfire management in the Park and surrounding montane forests. iii  Preface My research in Jasper National Park is part of a research program on fire history and climate-fire interactions in the western Canadian Cordillera that involves professors and students from the Universities of British Columbia, Guelph, Western Ontario and Brock. For Chapter 2, I resampled 29 sites established by the Foothills Research Institute (Rogeau 1999); however, I held primary responsibility for the site selection, sampling design, the collection and analysis of data. For Chapter 3, I recovered the data and samples from 172 sites established by the Foothills Research Institute (Rogeau 1999). I analysed the samples using crossdating to enable original climate-fire analyses. I prepared first drafts of all chapters. Throughout my research, I received constructive feedback and support from my supervisor, Dr. Lori Daniels, and editorial advice from all of my committee members: Drs. Peter Marshall, Sarah Gergel and Ze’ev Gedalof. iv  Table of Contents Abstract .......................................................................................................................................... ii Preface ........................................................................................................................................... iii Table of Contents ......................................................................................................................... iv List of Tables .............................................................................................................................. viii List of Figures ............................................................................................................................... ix List of Abbreviations ................................................................................................................... xi Acknowledgements ..................................................................................................................... xii Dedication ................................................................................................................................... xiv Chapter 1: Introduction ................................................................................................................1 1.1 Fire as a Disturbance Agent ............................................................................................ 1 1.2 Fire Regimes ................................................................................................................... 2 1.3 Research on Fire Regimes .............................................................................................. 4 1.4 Drivers of Fire ................................................................................................................. 6 1.4.1 Bottom-up controls ..................................................................................................... 6 1.4.2 Top-down controls ...................................................................................................... 8 1.4.3 Teleconnection interactions ........................................................................................ 8 1.4.4 Relative importance of bottom-up and top-down controls ....................................... 13 1.5 Fire and Forest Dynamics ............................................................................................. 14 1.6 Human Impacts on Fire Regimes .................................................................................. 15 1.7 Climate Change Impacts on Fire Regimes.................................................................... 18 1.8 Fire Regime Research in Jasper National Park, Alberta, Canada ................................. 20 1.9 Research Objectives ...................................................................................................... 22 v  Chapter 2: Historical Fire Frequency and Severity in Jasper National Park, Alberta, Canada ..........................................................................................................................................24 2.1 Introduction ................................................................................................................... 24 2.2 Study Area .................................................................................................................... 28 2.3 Materials and Methods .................................................................................................. 29 2.3.1 Site selection ............................................................................................................. 29 2.3.2 Fire scars ................................................................................................................... 29 2.3.3 Forest composition and structure .............................................................................. 30 2.3.4 Cohorts and veteran trees .......................................................................................... 31 2.3.5 Fire frequency and severity ....................................................................................... 32 2.3.6 Fire history and stand dynamics ............................................................................... 33 2.3.7 Successional trajectories ........................................................................................... 34 2.4 Results ........................................................................................................................... 35 2.4.1 Forest composition and structure .............................................................................. 35 2.4.2 Fire history ................................................................................................................ 35 2.4.3 Fire frequency and severity ....................................................................................... 36 2.4.4 Fire history and stand dynamics ............................................................................... 37 2.4.5 Successional trajectories ........................................................................................... 39 2.5 Discussion ..................................................................................................................... 40 2.5.1 Frequency and severity of historic fires .................................................................... 40 2.5.2 Changes to the fire regime during the 20th century ................................................... 41 2.5.3 Forest dynamics and influence of the historical fire regime ..................................... 43 2.5.3.1 Stand dynamics ............................................................................................... 43 vi  2.5.3.2 Impacts of fire exclusion on successional trajectories .................................... 45 2.6 Conclusion .................................................................................................................... 48 Chapter 3: Temporal Climate-Fire Relations ...........................................................................60 3.1 Introduction ................................................................................................................... 60 3.2 Materials and Methods .................................................................................................. 65 3.2.1 Research design ........................................................................................................ 65 3.2.2 Field sampling ........................................................................................................... 65 3.2.3 Laboratory analysis ................................................................................................... 66 3.2.4 Fire history ................................................................................................................ 66 3.2.5 Local Pseudotsuga menziesii chronology as a proxy of drought .............................. 67 3.2.6 Climate-fire relations ................................................................................................ 69 3.2.7 Twentieth century climatic conditions and fire occurrence ...................................... 70 3.3 Results ........................................................................................................................... 71 3.3.1 Fire history ................................................................................................................ 71 3.3.2 Pseudotsuga menziesii chronology as a proxy of drought ........................................ 72 3.3.3 Climate-fire relations ................................................................................................ 72 3.3.4 Fire occurrence and drought ..................................................................................... 73 3.4 Discussion ..................................................................................................................... 74 3.4.1 Climatic variation and historic fires in Jasper National Park ................................... 74 3.4.2 Multi-decadal variation in fire frequency ................................................................. 77 3.5 Conclusion .................................................................................................................... 81 Chapter 4: Conclusions ...............................................................................................................95 4.1 Summary and Contribution to Research ....................................................................... 95 vii  4.1.1 Importance of dendrochronological analyses ........................................................... 95 4.2 Management Implications ............................................................................................. 96 4.2.1 Fire regimes and management .................................................................................. 96 4.2.2 Importance of mixed-severity fires for at risk Rangifer tarandus and Ursus arctos populations ............................................................................................................................ 98 4.3 Future Research ............................................................................................................ 98 4.3.1 Importance of human versus lightning ignitions ...................................................... 98 4.3.2 Monitoring regeneration and fuel ............................................................................. 99 4.3.3 Climate-fire interactions ........................................................................................... 99 References ...................................................................................................................................101 viii  List of Tables Table 2.1 Site attributes and species composition of the 29 study sites in the montane forests of Jasper National Park ..................................................................................................................... 49 Table 2.2 Fire record descriptive statistics of the 29 study sites in the montane forests of Jasper National Park ................................................................................................................................ 51 Table 3.1 Summary of the fire records for 115 sites west of the Athabasca River ...................... 83 Table 3.2 Summary of the fire records for 57 sites east of the Athabasca River.......................... 85    ix  List of Figures Figure 1.1 Fire history study areas in Jasper National Park, Alberta, Canada ............................. 23 Figure 2.1 Fire history study area in Jasper National Park (top). The 29 fire-history sites in the Athabasca River valley, 15 km north of Jasper townsite (bottom) ............................................... 52 Figure 2.2 Size-structure histograms of trees (dbh ≥ 5 cm) by species for the 29 fire-history sites located along eight transects ......................................................................................................... 53 Figure 2.3 Age-structure histograms of trees (dbh ≥ 5 cm) by species for the 29 fire-history sites located along eight transects ......................................................................................................... 54 Figure 2.4 Fire history from 1550 to 2012 at all 29 sites .............................................................. 55 Figure 2.5 Species-specific lags in tree establishment following (a) predominantly less severe fires causing scars (left column) and (b) high-severity fires initiating cohorts only (right column)....................................................................................................................................................... 56 Figure 2.6 Comparison of age- and size-structure continuity (top), evenness (middle) and diversity (bottom) between fire severity classes ........................................................................... 57 Figure 2.7 Mean and standard errors of importance values by coniferous species and deciduous trees according to fire history class (columns) and canopy layer (rows) ...................................... 58 Figure 2.8 Mahalanobis distances between canopy and fire history classes. Shorter (longer) distances imply greater similarity (difference) between classes ................................................... 59 Figure 3.1 Fire history sites (n = 172) in the Athabasca River valley in montane and subalpine forests of Jasper National Park ..................................................................................................... 86 Figure 3.2 Fire history records from 1465 to 2012 at 172 sites .................................................... 87 Figure 3.3 Composite fire records from 1600 to 2012 for a) the 115 sites west of the Athabasca River, b) the 57 sites east of the Athabasca River and c) all 172 sites in the study area .............. 88 x  Figure 3.4 Climate-growth relations for Pseudotsuga menziesii from 1902 to 2009 ................... 89 Figure 3.5 Fire occurrence (black dots) from 1646 to 1985 relative to inter-annual to multi-decadal variation in climate .......................................................................................................... 90 Figure 3.6 Departure (%) from the mean of fire years (year 0) relative to the four years preceding and two years following fire for the a) residual chronology, b) ENSO, c) PDO and d) AMO climate patterns from 1642 to 1917 .............................................................................................. 91 Figure 3.7 Tests of association between fire (black) and non-fire (white) years and climatic variation ........................................................................................................................................ 92 Figure 3.8 Annual ring-width indices by fire years and periods from 1646 to 2009 .................... 93 Figure 3.9 Annual precipitation (top), maximum temperature (middle) and heat-moisture indices (bottom) by period from 1916 to 2009 ......................................................................................... 94    xi  List of Abbreviations AMO – Atlantic Multidecadal Oscillation BC – British Columbia BNP – Banff National Park ca. – circa dbh – diameter at breast height ENSO – El Niño-Southern Oscillation IPCC – Intergovernmental Panel on Climate Change JNP – Jasper National Park m.a.s.l. – meters above sea level PDO – Pacific Decadal Oscillation SLP – sea level pressure SST – sea surface temperature TSLF – time since last fire USA – United States of America     xii  Acknowledgements For technical support, I acknowledge: Dr. J. Wilmshurst and D. Smith at Parks Canada, Dr. R. Bonar at Hinton Wood Products and Dr. D. Andison, Healthy Landscapes Program at the Foothills Research Institute.  For funding, I acknowledge: Hinton Wood Products and the Natural Sciences and Engineering Research Council of Canada for supporting my Industrial Postgraduate Scholarship. For leadership, I acknowledge: Dr. L. Daniels. For direct support, I acknowledge: Dr. D. Andison (Healthy Landscapes Program at the Foothills Research Institute); Dr. L. Daniels, G. Greene, S. Desroches, T. Martin, A. Dobko, O. Villemaire-Côté, (Tree-Ring Laboratory at the University of British Columbia); V. Leung, G. Lee, L. Gunther (Centre for Advanced Wood Processing and Timber Engineering at the UBC Faculty of Forestry); C. Johansson, N. Hodges, D. Aquino (UBC Forest Sciences Information Technology); H. Purves (Parks Canada GIS technician); Drs. S. Aitken, Z. Gedalof, S. Gergel, V. LeMay, P. Murphy, H. Nelson, M. Pisaric, T. Sullivan; T. Wang, S. Watts (university faculty); Drs. J. Innes, P. Marshall, C. Prescott, (Deans of the UBC Faculty of Forestry); B. Bresnahan (chainsaw instructor); G. Kosh, D. Naidu, R. Poirier-Vasic (UBC Faculty of Forestry officers and administrators); C. Seto, R. Cheng, C. Mutia, A. Chan, N. Thompson (UBC Department of Conservation and Forest Sciences); Drs. C. Hudecek-Cuffe and J. Elliott (archaeologists); UBC Faculty of Forestry custodians. For indirect support, I acknowledge: Elder L. Grant, Dr. P. Shaw (First Nations Languages Program); Dr. T. Jones, Dr. M. Amoroso, Dr. M. Baradeih, Dr. A. Srur, Dr. E. Arbellay, A. Innerd, T. Maertens, E. Jones, H. Marcoux, J. Amerongen Maddison, A. Pogue, A. Hussain, M. xiii  Labonté, H. Erasmus (Tree-Ring Laboratory at UBC); Drs. C. Breuil, A. Carroll, P. Evans, A. Kozak, R. Guy, R. Hamelin, J. Richardson (UBC Faculty of Forestry). For spaces and places, I acknowledge: the Tree-Ring Laboratory @ UBC; Association for Fire Ecology; UBC Acadia Family Housing, Faculty of Forestry Office of the Dean, CAWP, Department of Conservation and Forest Sciences, Faculty of Graduate and Postdoctoral Studies; Tree-Ring Society; Wildland Fire Canada; Musqueam First Nation; UBC; provinces of BC and Alberta; country of Canada. I also acknowledge the following: Gregory G. and Elizabeth W.; Anusheh and Rumana M.; Marvin B. and Miles P.; Marina R.; Alexandra P., Paul P., Ryan P, Norma W., Stephanie T., Jordan B., Anthony R., Arnaud D.G., Joane E., Ting P., Jiayin S., Fernanda T. (UBC Faculty of Forestry graduate students); David A., Lori D., Sarah A., Jacob A., Marshall and Aby; David R. and Samuel R. (East Creek, UBC Haney-Malcolm Knapp Research Forest); Patrick W. and Christine B. (Madagascar Conservation and Development); Yuli V.; Alice C.; Futao G.; Michel S.; Ska-Hiish M.; Michael T.; Sarah D.; past and current friendly neighbours and staff in UBC Family Housing; Kathleen L. and Catherine T. (UBC Gymnastics); Master Paul F., Michael E., Kenneth L. (World Taekwondo Federation); Luis P. (Jogo do Pau); Riyad Z. (UBC Kinematics); Niel D., Andrew D., Julian M., Marco N., Thomas P., David S. and their families; Francis N. (Shotokan); friends who shared spaces in different countries and academic places. I acknowledge my family, including my extended family; I hug each one of you, or remember a moment when I did so. In particular, I acknowledge Adam Chavardès for consistent patience, understanding and encouragement. Thank you. xiv  Dedication To the Athapascan, Algonkian and Salishan cultures, Jasper National Park, Seuk Jin Ko and Adam.   1  Chapter 1: Introduction  1.1 Fire as a Disturbance Agent In North American forests, fire is the dominant causal agent of disturbance (Swetnam and Betancourt 1990; Dale et al. 2001; Pierce et al. 2004; Schoennagel et al. 2004; Westerling et al. 2006). A disturbance is “a relatively discrete event in time which disrupts ecosystem, community or population structure and changes resources, substrate availability, or the physical environment” (White and Pickett 1985, p. 7). According to this definition, disturbances alter the state and trajectory of ecosystems, drive spatial heterogeneity among forest patches that are disturbed at different times, and drive temporal changes in forests (Franklin et al. 2002; Turner 2010).  Individual disturbance events are characterized by a set of descriptors organized into five dimensions including the causal agent, spatial factors, temporal factors, magnitude and synergism (Heinselman 1981; White and Pickett 1985; Turner et al. 1998; Morgan et al. 2001; Turner 2010). Spatial factors include the location and extent of fire including size and shape of the area burned. Temporal factors include the start and end dates of the fire event yielding the timing and seasonality of fire. Magnitude is measured in two ways. Fire intensity is the direct physical energy per unit area per unit time generated by the fire and is often measured as temperature or height of the flaming front. Fire severity is an indirect measure of the impact of fire on vegetation mortality and survival and depends on species adaptations and susceptibility to fire. Synergism includes the influence on and interaction with other disturbances such as an insect outbreak or a blowdown, which can increase the amount of surface and ladder fuels and 2  influence fire size and magnitude. Interactions can be immediate or lagged, depending on short- and long-term disturbance effects and legacies.  1.2 Fire Regimes A disturbance regime describes the spatial and temporal dimensions of successive disturbances affecting a delineated landscape over a determined time frame (White and Pickett 1985; Agee 1993; Turner 2010). Spatial dimensions include the distribution of events in a landscape and the associations with topography (e.g. elevation, slope aspect, steepness, and position and landscape configuration). Temporal descriptors vary depending on fire severity. If the fire regime is of low severity then the fire frequency is quantified as the number of fires per unit time or its inverse, the interval(s) between fires. If the fire regime is of high-severity then the fire frequency is quantified as a fire cycle or rotation, the years required to burn an area equal in size to the study area. Both approaches measure variation in frequency to estimate predictability, the scaled inverse function of variation in the fire frequency.  Of the disturbance descriptors for fire regimes, frequency and severity tend to be inversely related. These two descriptors are commonly used to identify a particular fire regime (Flannigan et al. 2003; Schoennagel et al. 2004; Wright and Agee 2004; Halofsky et al. 2011); although, fire intensity (Heinselman 1981; Johnson and Van Wagner 1985) and dominant or potential vegetation of an ecosystem (Agee 1981) have also been associated with fire regimes. Traditionally, research on fire regimes has focused on low- and high-severity fire regimes, at opposite sides of the fire-severity spectrum. Low-severity fire regimes are represented by frequent surface fires, which have minimal mortality effects on trees and reduce surface fuels, 3  hence the name stand-maintaining regimes (Agee 1993; Swetnam et al. 1999; Heyerdahl et al. 2001; Schoennagel et al. 2004). Conversely, high-severity fire regimes are represented by infrequent crown fires which have high mortality effects on trees and significantly reduce surface and canopy fuels, hence the name stand-replacing regimes (Agee 1993, 1997; Turner et al. 1994; Sibold and Veblen 2000).   Mixed-severity fire regimes describe the complex patterns and effects of heterogeneous fires across a range of spatial and temporal scales (Lertzman and Fall 1998; Perry et al. 2011). At the landscape scale, fires can burn with a range of severities simultaneously or through time (Halofsky et al. 2011). Temporally, successive fires at one location burn with a range of severities resulting in compositionally and structurally diverse stands (Heyerdahl et al. 2012). Fire severity fluctuates spatially and temporally due to the control by and interactions among weather, climate, topography, vegetation composition and structure, and historical disturbances including anthropogenic activities (Turner 2010; Perry et al. 2011).   Over the past 15 years, mixed-severity fire regimes have garnered increased recognition, particularly in mixed-conifer forests. However, the disturbance dimensions of mixed-severity fire regimes remain inadequately understood in comparison to low- and high-severity fire regimes (Halofsky et al. 2011; Perry et al. 2011; Marcoux et al. 2013). Improving understanding of mixed-severity fire regimes represents an opportunity for landscape managers to develop strategies for more sustainable harvest of timber, better conservation of biodiversity and supporting forest resilience to environmental change.  4  1.3 Research on Fire Regimes Traditionally, different research approaches and methods have been applied to reconstruct fire frequency, depending on the dominant fire regime and its distinctive impacts on forest structure (Amoroso et al. 2011). With the shift in research toward fire severity as a key attribute of fire regimes, new methods have been developed to measure residual living trees, propagules and structural legacies like snags and coarsewood after a fire to quantify severity. For recent fires, direct measurements can be made using remote sensing techniques (Soverel 2010). Remote sensing combined with field verification is used to detect fire severity through delineation and classification of disturbed patches using percent crown cover and canopy closure which indicate different levels of mortality and post fire remnants (Hessburg et al. 2007). It can be used to differentiate variable effects within a fire that leads to patches of low, moderate and high tree survivorship inside the fire perimeter (Lentile et al. 2006; Soverel 2010; Andison 2012).   For distinct past fires, severity can be indirectly measured using dendrochronological reconstructions of tree age structures including living and dead trees (Sherriff and Veblen 2006). Low-severity fires are represented by age structures in which ≥40% of trees survived the fire and the post-fire recruitment cohort includes ≤20% of trees in the stand (Sherriff and Veblen 2006). For high-severity fires, ≤19% of trees survive and the post-fire recruitment cohort includes ≥71% of trees (Sherriff and Veblen 2006). For moderate-severity fires, 20-70% of trees survive and the recruitment pulse includes 20-70% of trees (Sherriff and Veblen 2006).  5  Frequent, low-severity fires in which a high proportion of trees survive but form fire-scars often result in rich fire-scar records (Swetnam et al. 1999). To infer fire frequency in this type of disturbance regime, fire-scars preserved in the boles of trees are used (Agee 1993; Brown and Swetnam 1994; Heyerdahl et al. 2001). Fire years are determined by crossdating annual rings to ensure the exact calendar year is assigned to each fire scar (Dieterich and Swetnam 1984). For long-lived trees, fire-scar records provide fire event inventories over decades to centuries (Fulé et al. 1997; Brown et al. 1999). However, individual trees are not perfect recorders of fire. Once scarred, trees are more susceptible to subsequent scarring but not all fires will produce a scar on all trees (Swetnam et al. 1999). To alleviate this limitation, multiple-scarred trees are sampled within a site to provide a complete fire record at the site or stand level.   To understand historic fire size as well as frequency specific methods are required. Since fire frequency depends on the size of the area sampled, i.e., more fires are likely to be detected as the sampled area increases, the area sampled at each site should be consistent to directly compare fire frequency. Reconstructing fire size is challenging since all trees within the fire do not form scars and fire perimeters do not result in distinct boundaries that are persistent and visible in air photos (Swetnam et al. 1999). Instead, spatially explicit networks of sites can be sampled and burn likelihood models are used to estimate size (Jordan et al. 2005, 2008; Hessl et al. 2007; Kernan and Hessl 2010; Swetnam et al. 2011).  In contrast to low-severity fires, high-severity fires lead to even-aged forests in patches with distinct boundaries (Agee 1993). To quantify a high-severity fire regime, fire history across a landscape is summarized using stand-origin (Heinselman 1973) or time-since-fire (Johnson and 6  Van Wagner 1985) maps. The forests are mapped to delineate discrete forest stands (Johnson and Gutsell 1994). Stand tree ages and fire scars located at stand boundaries may be used to derive stand origin and in conjunction the time since last stand-replacing fire (Johnson and Gutsell 1994). The data are then summarized in a stand-origin map where the age class distribution is used to estimate the fire cycle and fire frequency (Heinselman 1973). However, this approach assumes all fires are high-severity, stand-replacing fires with distinct and persistent boundaries (Van Wagner 1978; Van Wagner et al. 2006). A modification of the stand-origin approach is obtained via time-since-fire maps. Time-since-fire maps delineate stands by the last fire event, which was not necessarily a stand-replacing fire (Johnson and Van Wagner 1985).   Given complexities inherent to mixed-severity fire regimes, a range of research approaches are necessary to quantify spatial and temporal variation at stand to landscape scales. To reconstruct fire history at the stand scale, tree-rings are used to find evidence of past fires of different severities through time (Amoroso et al. 2011). Evidence of low-severity surface fires are found in fire scars and in stands with uneven age structures and veteran trees (Swetnam et al. 1999; Heyerdahl et al. 2012). Conversely, high-severity stand replacing fires result in few or no veteran trees, even-aged stands and fast-growing shade-intolerant species (Turner 2010). Thus fire-scar records combined with detailed forest age structures can help to reconstruct fire history and quantify fire frequency and return intervals (Sherriff and Veblen 2006; Amoroso et al. 2011; Heyerdahl et al. 2012).  7  1.4 Drivers of Fire Regimes 1.4.1 Bottom-up controls Fire regimes are driven by bottom-up and top-down controls (Agee 1993; Cyr et al. 2007; Heyerdahl et al. 2001, 2007; Lertzman and Fall 1998; Perry et al. 2011). Bottom-up controls influence fuel abundance and combustibility, which determine the behaviour and spread of individual fires and cumulatively determine the fire regime through time (Rothermel 1983; Heyerdahl et al. 2007). Topography is a strong bottom-up control (Agee 1993; Sibold and Veblen 2000; Taylor and Skinner 2003). Due to orographic effects, an increase in elevation is related to a decrease in temperature and an increase in precipitation such that low elevations are warm and dry and high elevations are cool and moist (Agee 1993). The differences in microclimate affect productivity along the elevation gradient and influence forest composition, structure and fuel abundance (Heyerdahl et al. 2001). Growing seasons and fire seasons are longer at low elevations compared to high elevations, resulting in increased fuel combustibility and more frequent but less severe fires (Agee 1993; Heyerdahl et al. 2001).  Local-scale slope aspect, steepness and position also affect fire behaviour and spread resulting in different fire effects and regimes (Agee 1993). In the northern hemisphere, westerly and southerly aspects tend to have warmer and drier local climates, whereas easterly and northerly aspects tend to be cooler and more mesic (Barrett 1988; Taylor 2000; Heyerdahl et al. 2007). Steeper slopes lead to accelerated fire spread (Heinselman 1981; Barrett 1988; Agee 1993). Fires igniting at the top of a slope tend to spread downhill or laterally, described as backing and flanking behaviour, respectively (Agee 1993). More common, fires igniting at the bottom of a slope tend to have head fire behaviour with greater effects (Agee 1993). Landscapes 8  configured with narrow valleys and mountain passes can funnel winds which drive the movement of fire, whereas streams and unproductive soils can hinder fire spread (Romme and Knight 1981; Agee 1993; Taylor and Skinner 1998, 2003). Landscapes with complex topography are often documented as driven by bottom-up controls influencing fire effects and regimes (Veblen et al. 2000; Heyerdahl et al. 2001; Schoennagel et al. 2004; Heyerdahl et al. 2007).   Site-level disturbance history is another bottom-up control (Agee 1993; Taylor and Skinner 2003; Schoennagel et al. 2004). Disturbance history includes, but is not limited to, past fires, bark beetle epidemics, extensive blowdowns, and human impacts such as fire exclusion (Turner 2010). The disturbance(s) can lead to changes in fuel accumulation influencing fire behaviour, effects and regimes (Agee 1993; Taylor and Skinner 2003; Schoennagel et al. 2004).  1.4.2 Top-down controls Weather and climate are top-down controls which limit fire occurrence and directly affect fire regimes at regional scales (Cyr et al. 2007). Weather, the condition of the atmosphere at a given place and time, influences fire occurrence and behaviour (Agee 1993). Warm temperatures, low relative humidity, and strong winds decrease fuel moisture, whereas precipitation increases it. Combined, these weather attributes affect fuel combustibility, probability of ignition, and rate of fire spread (Agee 1993; Taylor et al. 1996). Climate, the statistics of weather events at a given place over a given period of time, influences fire regimes (Swetnam and Betancourt 1990; Swetnam 1993). Spatial variation in climate determines the location and extent of droughts and wetter than normal conditions (Swetnam and Betancourt 1990; Watson and Luckman 2001a, 2001b, 2002, 2004, 2005; Mote et al. 1999; Pohl et al. 2002; 9  Westerling et al. 2006; Swetnam and Anderson 2008). Inter-annual to inter-decadal scale variation in climate determines the frequency of droughts conducive to fire or wet intervals hindering fire (Hessburg et al. 2005; Schoennagel et al. 2005).   Dry conditions conducive to fire in western North America have been associated with the El NiñoSouthern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) (Kitzberger et al. 2007; Swetnam and Anderson 2008). These oscillations exhibit complex teleconnections and interactions driving regional climate patterns. ENSO results from oceanic-atmospheric interactions originating in the tropical Pacific and Indian Oceans with teleconnections throughout the Pacific basin (Cook 1992; Diaz and Kiladis 1992; Allen 2000). ENSO is manifest through fluctuations between opposite phases called La Niña and El Niño, reoccurring intermittently over periods of 2-7 years (Cook 1992; Diaz and Kiladis 1992; Allen 2000). During La Niña phases, high sea level pressure (SLP) dominates the eastern tropical Pacific Ocean strengthening the easterly tradewinds across the surface of the tropical Pacific so that warm surface waters accumulate in the western Pacific and cool surface waters occupy the eastern Pacific (Sarachik and Cane 2010). The conditions are reversed during El Niño phases. The SLP differential weakens or reverses and warm surface waters spread across the equatorial Pacific Ocean and accumulate along the coasts of North and South America (Sarachik and Cane 2010). The variation in coastal sea surface temperature (SST) affects the strength and latitudinal position of the northern subtropical high pressure ridge located between ca. 30°N (border between the northern Sonora region, Mexico and southern California, United States of America (USA)) and ca. 50°N (border between northern Washington State, USA and the southern portion of the province of British Columbia (BC), Canada) depending on the ENSO 10  phases and season. In combination, the SSTs and subtropical ridge influence the temperature and moisture of air masses over western North America (Mote et al. 1999; Kitzberger et al. 2001; Sarachik and Cane 2010). In particular, at different locations of western North America ENSO tends to influence winter-spring precipitation with decreased (increased) rates which can facilitate (hinder) fire activity during the growing season (Mote et al. 1999; Kitzberger et al. 2001; Westerling and Swetnam 2003). During El Niños, the subtropical ridge is located further north towards 50°N due to warmer surface coastal waters. During winter and the subsequent spring, dry air masses persist in the Pacific and inland northwest North America including southern BC (Mote et al. 1999; Pohl et al. 2002; Westerling and Swetnam 2003; Heyerdahl et al. 2008). The location of the ridge and air masses redirect wet air masses into the southwest USA (Cole et al. 2002; Westerling and Swetnam 2003) and onto the coasts of northern BC and Alaska (Minobe 1997; Gershunov et al. 1999; Mantua and Hare 2002; Hartmann and Wendler 2005).   The conditions are different during La Niña phases with the subtropical ridge located further south towards 30°N due to cooler coastal surface waters. During winter and the subsequent spring, dry air masses persist in the southwest USA (Cole et al. 2002; Westerling and Swetnam 2003). The southern location of the ridge deflects storms northward such that cool, wet air masses flow into the Pacific and inland northwest North America (Mote et al. 1999; Pohl et al. 2002; Westerling and Swetnam 2003; Daniels et al. 2007; Heyerdahl et al. 2008) and onto the coasts of northern BC and Alaska (Mantua and Hare 2002; Hartmann and Wendler 2005). The strength and latitudinal position of the northern subtropical high pressure ridge also depends on seasonality. During the summer, the subtropical ridge shifts towards 50°N such that the Pacific and inland northwest North America are dry and warm whereas wet air masses are deflected 11  northward towards the coasts of northern BC and Alaska (Sarachik and Cane 2010). The condition of the air masses over a given location influence fire activity and consequently high fire activity tends to occur in the southwest during La Niña phases and in the Pacific and inland northwest during El Niño phases (Morgan et al. 2001).  The PDO is defined as the leading mode of Pacific Ocean SST variability north of 20°N (Mantua et al. 1997; Minobe 1997, 2000) and is strongly correlated to winter SLP in the North Pacific related to the intensity of the Aleutian Low located ca. 60°N (Beamish et al. 1997; Wyatt et al. 2011). The PDO varies over periods of 20 to 40 years, oscillating between positive, warm and negative, cool phases (Gedalof and Smith 2001; Mantua and Hare 2002), which drive multi-decadal climatic regimes in western North America (Cole et al. 2002; Smith et al. 2004; Heyerdahl et al. 2008; Trouet et al. 2009). During the positive phase of the PDO, the Aleutian Low is intensified, drawing warm, wet air masses towards North America (Mote et al. 1999; Mantua and Hare 2002; Pohl et al. 2002; Hartmann and Wendler 2005); however, the distribution of moisture depends on the position of the subtropical high pressure ridge and the jet stream. An intensified Aleutian Low diverts the regional jet stream northward and southward of the subtropical high, forcing storms to bypass the Pacific and inland northwest North America, whereas a weakened and displaced Aleutian Low directs rainstorms to the Pacific and inland northwest North America (Mote et al. 1999; Pohl et al. 2002). The combined effect of western North American coastal SSTs, the Aleutian Low, the subtropical ridge and the regional jet stream creates wet/dry dipole occurring between 30 and 50°N over western North America (Swetnam and Anderson 2008; Taylor et al. 2008).  12  The AMO is a pattern of multidecadal variability in the North Atlantic Ocean SST (averaged across 0-60°N and 75-7.5°W) influenced by the Atlantic Meridional Overturning Circulation (Kerr 2000; Sutton and Hodson 2003; Wyatt et al. 2011). The AMO varies between warm (positive) and cool (negative) phases every 50-100 years and causes temperature and precipitation deviations in western USA over decades (Swetnam and Betancourt 1998; Enfield et al. 2001; Gray et al. 2004; McCabe et al. 2004, 2008; Sutton and Hodson 2005; Brown 2006; Knight et al. 2006; Wang et al. 2010; Wyatt et al. 2011). During the positive phase of the AMO, warm, dry air masses tend to occur over the southwest USA between March and November (Knight et al. 2006; Wang et al. 2010) and wet air masses occur over the northwest USA except for the summer season (Wang et al. 2010).  1.4.3 Teleconnection interactions  The teleconnections interact and influence fire activity in different parts of western North America. El Niño influences on regional precipitation and temperatures are enhanced during positive PDO phases but moderated during negative PDO phases (Gershunov and Barnett 1998; Cole et al. 2002; Westerling and Swetnam 2003; Heyerdahl et al. 2008). Conversely, La Niña influences are enhanced during negative PDO phases but moderated during positive PDO phases. Wang et al. (2010) found negative PDO/La Niña and positive AMO phases resulted in regional drought conditions in southwest USA whereas in northwest USA, regional drought conditions were related to positive PDO/El Niño and negative AMO phases (Hidalgo 2004; McCabe et al. 2004; Sutton and Hodson 2005). The resulting regional droughts in different parts of western North America which were related to the interactions between the ENSO, PDO and AMO, were also associated with widespread wildfires (Kitzberger et al. 2007; Trouet et al. 2010). 13   1.4.4 Relative importance of bottom-up and top-down controls The relative importance of bottom-up and top-down controls on fire regimes varies by type of ecosystem and by location (Schoennagel et al. 2004; Meyn et al. 2007). In dry, lower-elevation forests such as ponderosa pine (Pinus ponderosa Douglas ex C. Lawson) woodlands or higher-elevation open pine forests in the southwest USA, bottom-up controls tend to be most limiting (Baisan and Swetnam 1990; Grissino-Mayer and Swetnam 2000; Heyerdahl et al. 2006). Fuels are sufficiently desiccated by the regular periods of warm, dry weather that climate is less of a fire regime control. Instead, fine fuel and ladder fuel accumulation limits fire spread (Fulé et al. 1997; Hessburg et al. 2005; Heyerdahl et al. 2006) and short periods of above-average moisture conditions can enhance fuel production (Baisan and Swetnam 1990; Grissino-Mayer and Swetnam 2000).  In cool, humid and dense higher-elevation subalpine forests and boreal forests, fire occurrence is most limited by top-down regional climate (Payette 1992; Turner and Romme 1994; Agee 1997; Buechling and Baker 2004; Schoennagel et al. 2004; Podur and Martell 2009). A significant drying period is necessary for fuel combustion (Agee 1993). In long periods between infrequent fires fuels accumulate (Veblen 2000; Schoennagel et al. 2004). Fires burn during the infrequent droughts and the effects are severe (Sibold and Veblen 2000; Buechling and Baker 2004). In subalpine and boreal forests, climate predominantly influences fire severity and spread through fuel desiccation and wind, not fuel abundance (Schoennagel et al. 2004; Podur and Martell 2009).  Mixed-severity fire regimes include low- to moderate-severity, stand-maintaining fires and high-severity, stand-replacing fires at stand and landscape scales because 14  of complex interactions between bottom-up and top-down controls driving fire at the stand level (Agee 1998; Lertzman and Fall 1998; Taylor 2000; Heyerdahl et al. 2001, 2012; Buechling and Baker 2004; Schoennagel et al. 2004; Arno and Fiedler 2005; Baker et al. 2007; Amoroso et al. 2011; Halofsky et al. 2011; Perry et al. 2011).  1.5 Fire and Forest Dynamics Fires of different frequency and severity strongly influence forest development and dynamics (Taylor and Skinner 1998, 2003; Fulé et al. 2003; Van Wagner et al. 2006; Amoroso et al. 2011; Perry et al. 2011; Halofsky et al. 2011). Low-severity fires cause mortality of understory plants but mature, fire-tolerant thick-barked trees survive (Swetnam and Baisan 1996; Kimmins 2004; Hessburg et al. 2007). Following low-severity fires in which <20% of trees die, growing space and resources remain limited for subsequent tree establishment (Schoennagel et al. 2004; Heyerdahl et al. 2006). Following repeated low-severity fires, the resulting forests are heterogeneous, composed of patches of regeneration and uneven-aged canopy trees with few subcanopy trees recruiting to the canopy over any given decade (Agee 1993; Schoennagel et al. 2004; Hessburg et al. 2007; Heyerdahl et al. 2012).   In contrast, following a high-severity fire in which ≥80% of trees die and mineral soil is exposed, the open growing conditions are conducive to regeneration of exposure-requiring and shade-intolerant species (Turner et al. 1997; Schoennagel et al. 2004, Turner 2010), as well as some species that tolerate but do not require shade (Antos and Parish 2002). Following canopy closure and the stem-exclusion stage of stand development (Oliver and Larson 1996), subcanopy conditions favour the regeneration of shade-tolerant species, which are often thin-barked and 15  fire-intolerant. In mature stands, canopy gaps form as trees die which release the growth of subcanopy shade-tolerant trees and facilitate establishment of new trees (Oliver and Larson 1996). The resulting increase in structural diversity also increases ladder fuels (Oliver and Larson 1996; Franklin et al. 2002; Turner 2010). Over long periods between fires, these processes result in structurally complex, uneven-aged forests of predominantly shade-tolerant but thin-barked fire-intolerant trees (Agee 1993; Schoennagel et al. 2004; Van Wagner et al. 2006; Turner 2010).   Mixed-severity fire regimes do not fit traditional successional trajectories and stand development stages due to the variation in fire effects within and among fires (Fulé et al. 2003; Halofsky et al. 2011; Perry et al. 2011; Marcoux et al. 2013). Since individual fires may be of low, moderate or high severity, variable amounts of subcanopy and canopy trees are killed. As a result, changes in stand structure and composition, patterns of post-fire recruitment and age cohort structure are also variable (Agee 1998; Hessburg et al. 2007; Amoroso et al. 2011; Marcoux et al. 2013). Thus, mixed-severity fire regimes result in forests with more complex species, structures and dynamics (Hessburg et al. 2007; Halofsky et al. 2011; Heyerdahl et al. 2012; Marcoux et al. 2013).  1.6 Human Impacts on Fire Regimes Human impacts on fire regimes vary among forest types, given differences in accessibility, land-use and the relative importance of fuels versus climate for determining fire frequency and severity (Schoennagel et al. 2004). Low-elevation forests are more accessible and land-use practices such as fire ignition, logging, livestock grazing, and fire suppression have 16  strongly influenced fire regimes (Barrett and Arno 1982; Veblen et al. 2000; Taylor and Skinner 2003; Schoennagel et al. 2004; Jensen and McPherson 2008). In North America, frequent ignitions by First Nations people (also known as Native Americans in the USA) added to fire occurrence caused by lightning (Barrett and Arno 1982; Dey and Guyette 2000; Turner et al. 2003; Murphy et al. 2007; Miller 2010). First Nations used fire as a management tool to facilitate the growth of food plants, improve forage for grazers, drive animals when hunting, clear vegetation along travel corridors and to reduce wildfire hazards around communities (Lewis 1985; Bahre 1991; Agee 1993; Kay 1995; Murphy et al. 2007; Miller 2010). As Europeans arrived and settled throughout North America, First Nations were displaced to reserves (Neu and Graham 2006) and their traditional use of fire declined (Malone et al. 1991). As more Europeans arrived and settled, they used fire to clear land for housing, pastures and mineral exploration and to burn logging slash (Barret and Arno 1982; Wadleigh and Jenkins 1996). Logging practices and areas cleared for mines, towns and livestock grazing changed forest structure, composition, and fuels and as a result indirectly reduced and excluded fire (Covington and Moore 1994a, 1994b; Veblen et al. 2000). As the interface between European settlements and the forest increased in North America, laws to ban burning were implemented to protect settler values (Cohen and Miller 1978; Rhemtulla et al. 2002). Prohibition of fire use, followed by placement of towers and roads into landscapes, firefighter training, improved vehicle access and, most recently, detection of cloud-to-ground lightning have increased the capacity to detect and rapidly suppress fires (Tande 1979; Murphy 1985, 2007; Murphy et al. 2007; Fulé et al. 1997; Brown et al. 1999; Taylor 2000; Veblen et al. 2000; Arienti et al. 2006). The resulting changes in fire frequency and associated changes to fire severity have been most prevalent in low-elevation forests, although evidence suggests mid-elevation montane forests were also subject to these 17  changes in fire regimes (Tande 1977, 1979; Rhemtulla et al. 2002; Schoennagel et al. 2004; DaSilva 2009; Nesbitt 2010; Amoroso et al. 2011; Greene 2011; Marcoux et al. 2013)   In contrast to low-elevation dry forests, fire frequency and severity have changed less during the 20th century in high elevation subalpine forests and boreal forests where fires historically were less frequent (Turner et al. 2003; Schoennagel et al. 2004). Over the past century, relatively few people lived in these forests and land-use impacts are minor compared to impacts in low elevation and montane forests (Romme and Despain 1989; Masters 1990; Johnson 1992). Moreover, since fuel combustibility controlled by pronounced droughts are more limiting for fire than fuel availability, the fire regime is less altered by land use change (Romme and Despain 1989; Johnson and Wowchuk 1993). These interpretations assume most historic ignitions were due to lightning, and that fire suppression has had no significant effects on the fire regime (Romme and Despain 1989; Nash and Johnson 1996; Johnson et al. 2001). However, human ignitions by First Nations peoples had impacts on fire regimes in subalpine forests and even in northern Canadian boreal forests (Kipfmueller and Baker 2000; Miller 2010). In addition, significant fire suppression impacts were identified on fire regimes in subalpine forests and relatively remote northern Canadian boreal forests (Kipfmueller and Baker 2000; Cumming 2005; Podur and Martell 2009).  Although fire exclusion and suppression have had effects on all types of fire regimes, the impacts have been greatest at valley-bottom and in montane forests historically characterized by low- and mixed-severity fire regimes, respectively (Schoennagel et al. 2004; Beaty and Taylor 2008; Perry et al. 2011). Suppression efforts are most effective in putting out low- and moderate-18  severity fires (Arienti et al. 2006) as opposed to high-severity fires which burn under extreme weather conditions and are difficult to suppress (Johnson et al. 2001). In absence of low- and moderate-severity fires as a result of fire exclusion and suppression, many low-elevation forests and montane forests have changed in composition, structure and fuels (Rhemtulla et al. 2002; Amoroso et al. 2011; Heyerdahl et al. 2012). In forests with low-severity fires regimes, fire exclusion and suppression facilitates tree infilling and the development of ladder fuels which increase the risk of high-severity fires (Swetnam and Baisan 1996; Swetnam et al. 1999; Schoennagel et al. 2004). In mixed-severity fire regimes, absence of low- and moderate-severity fires may homogenize the landscape with multi-cohort, mixed-species stands replaced by single cohorts of post-fire colonizers following high-severity fires (Agee 1998; Margolis and Balmat 2009; Bekker and Taylor 2010; Perry et al. 2011).   1.7 Climate Change Impacts on Fire Regimes Climatic trends observed during the 20th century and projected climate change impacts include increased frequency, duration, and severity of droughts in western North America (Dale 2001; Gedalof et al. 2005; IPCC 2007a, 2007b, 2013; Seager et al. 2007; Allen et al. 2009). Due to the established link between climatic variability and fire (Agee 1993; Grissino-Mayer and Swetnam 2000; Flannigan et al. 2008), projected changes in climate may lead to increased occurrence of large and higher-severity wildfires in North America (Flannigan et al. 2003; McKenzie et al. 2004; Westerling et al. 2006). Understanding spatial and temporal variation in climatic effects on fire regimes is therefore important for understanding potential effects of global warming (IPCC 2007a, 2007b, 2013).  19  The effects of climate change will differ among fire regimes; however, over western USA, increased wildfire activity was associated with increased spring and summer temperatures and earlier spring snowmelt (Westerling et al. 2006). In low-severity fire regimes such as in the southwestern USA, increased wildfire activity has been linked to a trend of warming temperatures and increasing variability in moisture conditions, with wetter conditions promoting biomass growth and drier conditions promoting drought and burning (Baisan and Swetnam 1990; Grissino-Mayer and Swetnam 2000). Swetnam et al. (1999) expressed the need to better understand how global climate change may alter tree species distribution and ensuing fuel conditions, thus potentially shifting historically low-severity fire regimes towards higher-severity fire regimes. However, Grissino-Mayer and Swetnam (2000) argued that altered precipitation and temperature regimes would be unlikely to produce simple linear responses in fire regimes. In high-severity fire regimes, such as in the Canadian boreal forests, Flannigan et al. (2003) indicated fire regimes would respond rapidly to changes in climate. High-severity fire regimes in the subalpine and boreal forests may sustain more frequent fires with increasing fire season length and increased cloud-to-ground lightning with a corresponding increase in ignitions (Price and Rind 1994). Mixed-severity fire regimes in mid-elevation montane forests have been found at the juxtaposition between low- and high-severity fire regimes (DaSilva 2009; Nesbitt 2010; Amoroso et al. 2011; Greene 2011; Marcoux et al. 2013). Moreover, in some of these forests, recent wildfires have been of high-severity and burned during extreme fire weather (Agee 1993, 1998; Gedalof et al. 2005). A consequence of climate change for some forests historically characterized by mixed-severity fire regimes is a shift towards high-severity stand-replacing fires (Fulé et al. 2003; Schoennagel et al. 2004; Bekker and Taylor 2010). Thus, potential changes in 20  the global climate may alter not only the frequency of high-severity stand-replacing fires but also their proportion on North American landscapes.  1.8 Fire Regime Research in Jasper National Park, Alberta, Canada There is growing evidence in the Canadian Cordillera of mixed-severity fires in forests at montane elevations (Cochrane 2007; DaSilva 2009; Nesbitt 2010; Amoroso et al. 2011; Greene 2011; Kubian 2013; Marcoux et al. 2013). In Jasper National Park (JNP), Alberta, Canada, fire records have been developed from a network of sites surrounding the Jasper townsite (Tande 1977, 1979) and at two sites north of the townsite (Rogeau 1999) (Fig. 1.1). Tande (1977, 1979) and Rogeau (1999) analysed cross-sections from living and dead fire-scarred trees and years of origin from increment cores systematically collected from field sites. The years fire scars formed were used to establish a fire chronology and to estimate the year stands originated. The stand origin data were mapped to infer the extent of past fires.  Tande (1979) developed a fire chronology for a 310-year period (1665-1975) in which he reported 72 fires indicated by fire scars collected from a 43,200 ha study area. Based on this fire-scar record, he indicated there was one fire per year somewhere in the study area between 1894 and 1908. For the entire study area, fires occurred at one to nine year intervals from 1837 to 1971 and intervals were more variable ranging from 1 to 36 years from 1665 to 1834 (Tande 1979). Major fires, defined as those which burned at least 500 ha, occurred 24 times at intervals varying from 1 to 27 years and accounted for most of the area burned from 1665 to 1975 (Tande 1979). A strong decline in burned area after 1908 coincided with active fire suppression, which started in 1913 (Tande 1977, 1979; Murphy et al. 2007). 21   Rogeau (1999) developed a fire chronology for a 514-year period (1485-1999) which showed 15 fires indicated by fire scars and tree ages in a 3,300 ha study area. Fire-scar dates combined with tree ages suggested fires burned somewhere in the study area at one to seven year intervals from 1889 to 1915 and intervals were generally longer from 1798 to 1889, varying from 1 to 27 years (Rogeau 1999). Major fires initiating stands at more than ten sites occurred at longer intervals varying from 6 to 48 years (Rogeau 1999).  Tande’s (1977, 1979) and Rogeau’s (1999) studies include trees with multiple scars offering evidence of historic low- to moderate-severity fires; however, several limitations for quantifying mixed-severity fire regimes result from the stand-origin mapping approach they applied. First, Tande (1977, 1979) and Rogeau (1999) provide composite fire records for their study areas from which they calculated metrics of fire frequency and size, but their records do not indicate fire severity. The frequency values, including the means and ranges, apply to areas equal to the size of their study areas and are difficult to translate to different spatial scales. In addition, the fire-scar dates were not crossdated therefore they were not reliably annually-resolved. The two datasets reported consecutive fire years (e.g., fire intervals of one year), but did not account for false, incomplete and missing rings commonly associated with fire scars so actual fire return intervals may be longer than reported. This potential source of error affects the reconstructions of fire size, calculations of fire return intervals and fire frequency and limits the translation of the outcomes to guide stand-level management and treatments.  22  1.9 Research Objectives My research contributes to the understanding of mixed-severity fire regimes in mixed-conifer forests of the Canadian Cordillera. My objectives were: I) develop crossdated, annually-resolved fire-history records and determine stand age-structure for a spatially-explicit network of sites in the montane forests of Jasper National Park to estimate past fire frequency and severity; II) quantify effects of historic fires on contemporary forest dynamics inferred from forest structure and composition; and III) quantify effects of inter-annual to decadal variation in climate on historic fire occurrence. In Chapter 2, I test the hypotheses that: I) historical fires included high- and moderate-severity fires which comprised a mixed-severity regime; and II) fire suppression has reduced compositional and structural diversity of forests. I focused on understanding historic changes of stand dynamics and the fire regime in a 2,000 ha study area. To reconstruct fire history and forest dynamics and to detect fires of a range of severities at individual sites, I sampled 29 sites for tree composition, age- and size-structure and fire-scar data (Sherriff and Veblen 2006; Heyerdahl et al. 2012).  In Chapter 3, I test the hypothesis that historic fire occurrence depended on inter-annual to decadal variation in climate, but that climatic variation alone does not explain the recent absence of fire from the montane forests of JNP. I quantified the effects of drought, the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) on fire occurrence using crossdated fire records at the landscape-level in a 3,300 ha study area distributed east (1,900 ha) and west (1,400 ha) of the Athabasca River valley. I used the fire-scar data from the 29 sites in the second chapter, as well as reanalysed and crossdated fire scars and tree ages from 143 additional sites established and sampled by the 23  Foothills Research Institute between 1997 and 2000 (Rogeau 1999). I focused on the temporal variation of fire occurrence in the study area since past research on Tande’s fire-scar record indicated ENSO and the PDO had a significant influence on precipitation and fire regimes in JNP (Schoennagel et al. 2005).  In the final chapter, I discuss the implications of my findings for ecosystem management and conservation guided by natural range of variability and make recommendations for restoration of fire regimes to increase forest resilience to severe fires given the anticipated effects of climate change in Jasper National Park. Finally, I identify key avenues of future research.     Figure 1.1 Fire history study areas in Jasper National Park, Alberta, Canada. 0 25 kmJasper NationalPark boundaryRivers & lakesMontane ecoregionFire history study areasRogeau (1999)Tande (1977, 1979)Grid NorthJasperNationalParkTown ofJasperAthabasca R.24  Chapter 2: Historical Fire Frequency and Severity in Jasper National Park, Alberta, Canada  2.1 Introduction Fire is a driver of forest dynamics influencing stand-level composition and structure and landscape-level heterogeneity and diversity (Turner 2010). Accurate knowledge of historic fire severity and frequency is critical for understanding current forest conditions and successional trajectories, particularly where historic disturbance regimes are used to guide ecosystem-based management and conservation practices (Hessburg et al. 2007; Scholl and Taylor 2010; Turner 2010; Amoroso et al. 2011; Marcoux et al. 2013). Similarly, understanding disturbance regimes and their drivers is critical for anticipating the effects of climate change on forest dynamics (Dale et al. 2001; Millar et al. 2007).  In the Canadian Cordillera, the traditional interpretation of disturbance regimes is that infrequent high-severity fires dominate (Johnson et al. 1998, 2001). Under the influence of high-severity fires, forests tend to be even-aged with low structural diversity since each fire event kills >80% of trees and establishment occurs in pulses accounting for 71-100% of trees in a stand (Sherriff and Veblen 2006). When the interval between high-severity fires is short relative to the lifespan of the component tree species, structurally-complex and uneven-aged old stands are rare (Agee 1993; Turner et al. 1998; Turner 2010). The landscape is comprised of a mosaic of mostly even-aged stands that differ in age and stage of development depending on the time since each 25  last burned. Shade-intolerant pioneer species are more common that shade-tolerant, late-successional species.  Recent research in the Canadian Cordillera (Cochrane 2007; DaSilva 2009; Nesbitt 2010; Greene 2011; Marcoux et al. 2013) and Alberta Foothills (Amoroso et al. 2011) provides evidence that historic fire regimes included low-, moderate-, and high-severity fires and are better described as mixed-severity than high-severity fire regimes. A mixed-severity fire regime would explain the observed diversity in forest composition and structures, particularly in montane forests (Cochrane 2007; Nesbitt 2010; Marcoux 2013; Marcoux et al. 2013).  Low- and moderate-severity fires result in low tree mortality and, conversely, survival of 40-100% and 20-70% of trees within a stand, respectively (Sherriff and Veblen 2006). High levels of canopy tree survival limit opportunities for tree establishment so new cohorts account for less than 20% and 20-70% of trees, respectively (Sherriff and Veblen 2006). Moreover, variable effects within individual fires lead to patches of low, moderate and high tree survivorship inside the fire perimeter (Lentile et al. 2006). Fires with a range of severities can burn successively at one location or through time over a landscape resulting in compositionally and structurally diverse stands (Lertzman and Fall 1998; Heyerdahl et al. 2012). Given these complexities, forests with mixed-severity fire regimes do not fit traditional successional and stand development trajectories (Fulé et al. 2003; Halofsky et al. 2011). Rather, stands tend to develop uneven-age structures with distinct single to multiple cohorts, composed of diverse species with variable adaptations to fire and shade (Hessburg et al. 2007; Marcoux et al. 2013). Landscapes are heterogeneous with high variation in patch sizes and spatial patterns (Hessburg et al. 2007; Amoroso et al. 2011; Halofsky et al. 2011; Perry et al. 2011; Marcoux et al. 2013). 26   Human impacts on high- versus mixed-severity fire regimes have differed during the 20th century (Schoennagel et al. 2004). In general, high-severity fires are infrequent enough that fire suppression during the 20th century has had modest effects on fire frequency and forest composition, structure and fuel complexes (Romme and Despain 1989; Nash and Johnson 1996; Johnson et al. 2001; Fauria and Johnson 2008). However, land-use practices through fire exclusion and suppression have had significant impacts on some forests with mixed-severity fire regimes (Schoennagel et al. 2004; Beaty and Taylor 2008). Specifically, exclusion and suppression of low-to-moderate-severity surface fires alters forest composition, structure, fuels and successional trajectories (Agee 1993; Schoennagel et al. 2004; Amoroso et al. 2011). Sustained exclusion and suppression of fire contributes to homogenization of forests as shade-tolerant but fire-intolerant species establish, replacing fire-tolerant species within stands, increasing forest densities and adding ladder fuels (Beaty and Taylor 2008). These changes in composition and structure could make stands less resilient to lower-severity fires and more conducive to high-severity fires (Littell et al. 2010). Following higher-severity fires, multi-cohort, mixed-species stands are replaced by single cohorts of post-fire colonizers (Agee 1998; Perry et al. 2011), making the forests more consistent with those associated with a high-severity fire regime. In parallel, recent wildfires in montane forests have been of high-severity and burned during extreme fire weather (Filmon 2004; Gedalof et al. 2005), which could be the result of climate change (Dale et al. 2001; IPCC 2007a, 2007b, 2013).  Fire history research in the montane forest of Jasper National Park (JNP), Canada provides preliminary evidence of a mixed-severity fire regime. Tande (1977, 1979) and Rogeau 27  (1999) used increment cores to estimate stand-origin dates and counted rings on fire-scar samples. Unfortunately, the fire scars were not crossdated to account for false and missing rings so these fire dates are not accurate at an annual resolution. Nevertheless, the data were used to infer the extent of past fires and estimate fire return intervals for their respective study areas. Both studies reported frequent fires during the 1800s and early 1900s but few fires burned after 1913 (Tande 1977, 1979; Rogeau 1999) following active fire suppression (Murphy et al. 2007). Rhemtulla et al. (2002) used repeat photography to document a shift towards late-successional vegetation types and increased crown closure in coniferous stands in the Park. The changes were consistent with observations in other montane forests from which low-to-moderate-severity fires have been excluded and suppressed. Combined, these studies suggest a change in the fire regime and forests of JNP during the 20th century, potentially jeopardizing their resilience to fire and climate change.  Accurate estimates of historic fire frequency and severity are needed to fully understand the magnitude and effects of 20th century changes to fire regimes and forest dynamics in JNP. To address this knowledge gap, my research was designed to answer three questions: How frequent and severe were historic fires? Has the historic fire regime changed during the 20th century? How has fire history affected forest composition and structure? I focused on understanding historic changes to the fire regime and stand dynamics in a 2,000 ha study area. I sampled 29 sites for tree composition and size-structure and reconstructed historic fire frequency and severity by developing crossdated fire-scar chronologies and high-resolution age structures (Sherriff and Veblen 2006; Heyerdahl et al. 2012). I used these data to test the following hypotheses: I) 28  historical fires in the montane forests of JNP comprised a mixed-severity regime and II) fire exclusion and suppression have reduced compositional and structural diversity.    2.2 Study Area This research was conducted in Jasper National Park (JNP), Alberta, (Fig. 2.1) in the Main and Front Ranges of the Canadian Rocky Mountains (Tande 1979). Late Paleozoic limestone and Mesozoic shale underlie peaks and valleys respectively (Gadd 1986), whereas surface materials are till and glaciofluvial deposits comprised of sandstones and quartzites with slate and limestone (Stringer and LaRoi 1970). Gentle slopes and steep cliffs and ridges of exposed bedrock create a complex topography (Tande 1979). Soils are predominantly brunisols formed on glacial till, loess and outwash deposits (Tande 1977; Sanborn et al. 2011). Climate is subarctic (Longley 1970; Kottek et al. 2006). The instrumental records for 1981-2010 from the Jasper climate station (52°53' N, 118°04' W, 1,062 m.a.s.l.) (Environment Canada 2014) show mean annual precipitation was 392.6 mm, 22% of which fell as snow from September through June. Mean annual temperature was 3.6C, with mean monthly temperatures of 15.0 and -9.1C for July and December, respectively (Environment Canada 2014).  Three ecoregions are represented in JNP: the montane (1,000-1,350 m.a.s.l.), the subalpine (between 1,350 m.a.s.l. and tree line) and the alpine (above tree line) (Rhemtulla et al. 2002). This research was conducted in the montane ecoregion along the Athabasca River valley in JNP (Fig. 2.1). Forests in the montane ecoregion are dominated by lodgepole pine (Pinus contorta Douglas ex Loudon) and include Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco], white spruce [Picea glauca (Moench) Voss], Engelmann-white spruce natural hybrids (Picea 29  engelmannii Parry x Picea glauca; hereafter “Picea”), and trembling aspen (Populus tremuloides Michx.) interspersed with grasslands (Holland and Coen 1982; Rajora and Dancik 1999). Forests in the subalpine ecoregion are dominated by Picea and subalpine fir [Abies lasiocarpa (Hooker) Nuttall] (Holland and Coen 1982; Rajora and Dancik 1999; Peet 2000).  2.3 Materials and Methods 2.3.1 Site selection The study area is located 15 km north of the Jasper townsite (52°50' N, 118°05' W) on both sides of the Athabasca River valley (Fig. 2.1). I reconstructed fire history and stand dynamics at 29 sites originally sampled by Rogeau (1999). To create a stand-origin map for a 3,300 ha area, Rogeau (1999) sampled 180 sites along 36 transects. For this research, I selected eight widely distributed transects in the area; five transects were south or west and three transects were east of the Athabasca River. Sites were located approximately 350 m apart along transects and extended upslope from the montane into the subalpine ecoregion. To avoid bias, I selected sites independently of the fire evidence reported by Rogeau (1999). Of the 29 selected sites, 21 included fire-scarred trees and 8 sites had no scars (Rogeau 1999). Of the 151 not resampled sites, 106 included fire-scars, charred bark, charred logs/stumps and/or soil charcoal and the other 45 sites had no fire evidence.  2.3.2 Fire scars From the centre-point of each site, I searched a one hectare circular plot (radius = 56.4 m) for fire-scarred trees, snags, stumps and logs (hereafter “scarred trees”). A full or partial cross-section (Cochrane and Daniels 2008) was sampled from up to six scarred trees per site by 30  selecting the large trees and those with the most visible scar-lobes to maximize the fire record. This sampling design ensured sample areas were consistent from site to site and were directly comparable to other fire histories conducted in western Canada (Cochrane 2007; DaSilva 2009; Nesbitt 2010; Greene 2011; Marcoux 2013). When possible, fire-scar samples collected by Rogeau (1999) were included.  Fragile fire-scar samples were mounted on wooden supports and all samples were sanded following standard protocols (Stokes and Smiley 1996). I scanned high-resolution (1,200 or 2,400 dots per inch) digital images along radii from the bark to the inner-most ring including the tips of fire scars. Ring widths were measured using the program CooRecorder (Larsson 2011a). I visually crossdated and statistically verified the ring dates using the programs COFECHA and CDendro (Grissino-Mayer 2001a; Larsson 2011b) to determine the years of the inner-most and outer-most rings and individual fire scars (hereafter “fire-scar year”) (Grissino-Mayer 2001a).  2.3.3 Forest composition and structure I sampled forest composition and structure at the centre of each site using a modified n-tree design (Jonsson et al. 1992; Lessard et al. 2002; Heyerdahl et al. 2006). For stands with one canopy layer, I sampled the ten canopy trees or snags with diameter at breast height (dbh) ≥5 cm closest to the centre-point. For stands with multiple canopy layers, ten canopy and ten subcanopy trees or snags with dbh ≥5 cm were sampled. The distance and bearing from plot centre to the distal canopy and subcanopy tree were measured (Heyerdahl et al. 2006). For each tree, I recorded species, dbh (in cm), status (live or dead) and estimated age using increment cores. Cores were taken ca. 30 cm from the ground and aimed to include the pith. To account for 31  sapling regeneration, I searched a 100 m2 circular plot (radius = 5.64 m) from the centre-point of each site for saplings. I counted the number of live saplings which were ≥1.37 m in height and <5 cm in dbh and I recorded the species.  Like the fire-scar samples, cores were mounted on wooden supports, sanded following standard protocols (Stokes and Smiley 1996) and ring widths were measured using the program CooRecorder (Larsson 2011a). I visually crossdated and statistically verified the cores using the programs COFECHA and CDendro (Grissino-Mayer 2001a; Larsson 2011b) to determine the years of the inner and outer rings (Grissino-Mayer 2001a). Crossdating was performed using existing published Pseudotsuga menziesii chronologies that spanned from 1630 to 1965 (Ferguson and Parker 1965) and new chronologies for Pseudotsuga menziesii and Picea that I developed for each site and the region. Tree age estimates included corrections for cores that missed the pith (Duncan 1989) and the number of years for trees to grow to coring height (Powell et al. 2009; Daniels unpublished data). The total age correction averaged 12 years and 80% of ages had a correction ≤15 years. Therefore, the age structure of each site was represented using histograms with 15-year establishment classes.  2.3.4 Cohorts and veteran trees Even-aged cohorts were defined as 30-year periods when 25% of trees per site established (after Heyerdahl et al. 2012). To identify even-aged cohorts, I assessed the number of trees per 30-year period, starting from the pith date of the oldest tree, shifting one year at a time, and ending with the pith date of the youngest tree. Post-fire cohorts were the subset of even-aged cohorts that (a) coincided with a fire scar at the same site or (b) included the oldest trees at the 32  site. The fire year assigned to each post-fire cohort was (a) the fire-scar year or (b) the year preceding the establishment of the oldest tree in the cohort. Any tree that survived fire (e.g., established prior to a fire scar or post-fire cohort) was considered a veteran tree. At each site, I calculated the percentage of trees that were veterans, which I used to classify the severity of the last fire at the site as low (81-100%), moderate (20-80%) or high (0-19%) (adapted from Agee 1993; Sherriff and Veblen 2006).  2.3.5 Fire frequency and severity Composite fire chronologies were developed for each site using fire scars and post-fire cohorts. For each site-level fire chronology, I determined the length of the fire record, the number of fires, the minimum, mean and maximum intervals between fires, and time since last fire (TSLF). TSLF was calculated as the number of years from the most recent fire year (scar or initiation of a post-fire cohort) to the year 2012.  I used the presence of fire scars, even-aged cohorts and veteran trees to classify the severity of historic fires through time at individual sites (Sherriff and Veblen 2006; Heyerdahl et al. 2012).  Sites were classified as having evidence of a mixed-severity fire history based on the following criteria: (1) ≥2 fire years represented by scars, indicating low- to moderate-severity fires, and ≥1 even-aged cohort indicating moderate- to high-severity fire, or (2) a single fire-scar year preceded by veteran trees and ≥1 cohort. Sites were classified as having evidence of only high-severity fires based on the following criteria: (1) the oldest trees formed a cohort and there were no fire scars, or (2) the oldest trees formed a cohort and all fire scars coincided with it.  33  2.3.6 Fire history and stand dynamics I determined the lag between fire and tree establishment by identifying the fire-scar year or post-fire cohort preceding the establishment of subject trees (after Amoroso et al. 2011; Marcoux 2013). Lags were calculated as: (1) the difference between the fire-scar year and tree pith date indicating predominantly less severe fires causing scars or (2) the difference between the pith date of the oldest tree in the post-fire cohort and the subject tree, indicating that high-severity fires initiated the cohort. Frequency histograms of lag times relative to fire scars and post-fire cohorts were compared among species.   To further evaluate the effect of fire at the tree scale, I calculated average, initial and relative growth rates of trees (Amoroso et al. 2011). The average growth rate was the average ring width over the lifespan of the tree (radius inside bark divided by age in years), the initial growth rate was the average width of the ten rings closest to the pith, and the relative growth rate was the ratio of the initial growth rate divided by the average growth rate (Amoroso et al. 2011). I compared initial and relative growth rates among species and among less severe fires causing scars and high-severity fires initiating cohorts only.  To distinguish the influences of high- versus mixed-severity fires on stand dynamics, I calculated age- and size-structure diversity indices. The evenness index was the number of 15-year age or 5-cm size classes occupied by at least one tree (Marcoux et al. submitted). Low values denoted a narrow range and relatively even-aged (sized) stands; high values denoted a broader range and uneven-aged (sized) stands. The continuity index was the number of vacant 15-year age or 5-cm size classes within the range of occupied classes (Marcoux et al. submitted). 34  Age- and size-structures with no or few vacant classes were relatively continuous and a greater number of vacant bins denoted discontinuous stands. As well, I calculated the Shannon diversity index (Shannon and Weaver 1949) from the relative proportion of trees in each age or size class per stand. I compared evenness, continuity and diversity of the age and size structures between fire-severity classes using box plots and Mann-Whitney rank sum tests.  2.3.7 Successional trajectories To assess the influence of fire on successional trajectories, I compared forest composition and structure between canopy and subcanopy strata of sites with evidence of mixed- versus high-severity fires. Relative density and basal area per hectare were calculated for living trees and snags of each species and canopy stratum at each site. Populus tremuloides and balsam poplar (Populus balsamifera L.) occurred infrequently and at low abundances and were grouped (hereafter “deciduous trees”). For each site, importance values (IV) (Curtis and McIntosh 1951) for conifer species and deciduous trees were calculated as the sum of relative density and relative basal area of live trees and snags in the canopy and living trees in the subcanopy. This allowed a comparison between current and future canopy trees, assuming current subcanopy trees are potential future canopy trees. Multivariate discriminant analysis (MDA) (SAS 9.3) was used to compare IVs among four groups of trees: (1) the canopy layer of sites with mixed-severity fire history, (2) the subcanopy layer of sites with mixed-severity fire history, (3) the canopy layer of sites with high-severity fire history, and (4) the subcanopy layer of sites with high-severity fire history. Mahalanobis distances were used to assess similarity (low values) and differences (large values) among groups (Mahalanobis 1930; Dillon and Goldstein 1984).  35  2.4 Results 2.4.1 Forest composition and structure The forest at most sites was composed of mixed species and included two canopy strata which varied in density and basal area among sites (Table 2.1; Fig. 2.2). For sites with two canopy strata, the dominant canopy trees based on tree density were Picea (n = 15 sites), Pinus contorta (n = 8) and Pseudotsuga menziesii (n = 4), whereas Picea dominated the subcanopy. Two sites had a canopy dominated by Pinus contorta (≥90% of sampled canopy trees) but no subcanopy strata. Populus tremuloides was present at seven sites and balsam poplar was at one site.   At 20 sites, Picea saplings accounted for ≥50% of the regeneration. Of these 20 sites, 13 included Picea only. Four sites had only Pseudotsuga menziesii and one site had only Pinus contorta sapling regeneration. Sapling regeneration was absent at four sites.  2.4.2 Fire history Among the 29 sites, 20 had fire-scarred trees (Table 2.2) from which 64 fire-scarred cross-sections yielded 88 fire scars. Fires indicated by scars occurred in 13 separate years ranging from 1646 to 1905. Of the 560 sampled trees, I successfully aged cores from 458 live trees and 70 snags (n = 528 total). The oldest trees were Picea, which established in the 1500s (age >400 years) (Fig. 2.3); however, 70% of all trees established between 1820 and 1920.   Most trees (93%) established in even-aged cohorts dominated by Picea or Pinus contorta (Fig. 2.3). All sites had one or two cohorts, for a total of 34 cohorts, 33 of which likely originated 36  after fire. Eighteen cohorts coincided with a fire scar at the same site and 15 cohorts included the oldest trees at the site. Of the 15 cohorts including the oldest trees at the site, 10 cohorts included shade-intolerant Pinus contorta and Populus tremuloides, whereas the other 5 cohorts included trees with wide tree-ring patterns suggesting open-grown conditions. One cohort did not coincide with a fire scar and did not include the oldest trees at the site suggesting its establishment may have been stand dynamics or a disturbance other than fire.  Veteran trees were identified at 15 sites, within which they accounted for 5% to 95% percent of the sampled trees (Table 2.2; Fig 2.3). Based on the percentage of veteran trees, the severity of the last fire was classified as low at 2 sites, moderate at 9 sites, and high at 18 sites.     2.4.3 Fire frequency and severity Fire histories for individual sites ranged from 107 to 457 years based on the age of the oldest tree that could have recorded fire at each site (Fig. 2.3 and 2.4; Table 2.2). Nine sites had cohorts only, whereas 20 sites had cohorts and fire scars, with up to five fire-scar years per site. At the 11 sites with multiple fires, fire intervals ranged from 27 to 165 years. Time since last fire (TSLF) ranged from 107 to 193 years. The composite fire record (29 sites combined) included 13 fire years indicated by scars and 8 years indicated by the cohorts independent of fire scars. Widespread fires in 1772, 1827, 1889 and 1905 scarred trees and/or generated cohorts at five, nine, eight and seven sites, respectively. No fire scars were recorded after 1905 (Fig. 2.4).   At 18 of 29 sites, there was evidence of mixed-severity fires through time and the remaining 11 sites included evidence of high-severity fires only (Table 2.2). Of the sites with 37  mixed-severity fires, 11 had ≥2 fire-scar years, whereas 7 sites had one fire-scar year with veteran trees. Of the sites with multiple fire-scar years, two sites had high density of veteran canopy trees (>90%) and low post-fire regeneration suggesting the most recent fire was of low severity. In contrast, the age structure of four sites included a single cohort and no veterans, suggesting the last fire was high in severity. The other 12 mixed-severity sites included variable numbers of veterans and post-fire regeneration suggesting the recent fires sustained were of moderate (9 sites) or high-severity (3 sites). One to five fires were recorded per site and time since last fire (TSLF) averaged 129 ±31 years (mean ± standard deviation; range = 107 to 185 years).  Of the sites with high-severity fires, nine sites had one cohort which included the oldest trees at the site but had no scars. Two sites had one fire-scar year coinciding with a cohort which included the oldest trees at the site. TSLF was longer at the high-severity fire history sites (143 ±31 years; range = 107 to 193 years) than at the mixed-severity fire history sites.   2.4.4 Fire history and stand dynamics All three conifers established after both low- and moderate-severity fires (hereafter “lower-severity fires”) indicated by scars and high-severity fires that initiated cohorts (Fig. 2.5). Of the Pinus contorta, 73% established after fires causing scars. More than half (63%) of the estimated establishment dates for Pinus contorta were within 15 years and 88% within 30 years of fire, regardless of severity. Of the Pseudotsuga menziesii, 55% established after fires causing scars; however, only 50% of establishment dates were within 30 years of a fire scar and lags were up to 108 years. Pseudotsuga menziesii had shorter lags after more severe fires, with 86% 38  of trees establishing within 30 years of the oldest tree in post-fire cohorts and a maximum lag of 36 years. Picea regenerated in similar proportions after fire causing scars or initiating cohorts, with >75% of establishment dates within 30 years of fire but Picea had the longest lags of up to 117 years.    Initial growth rates for Pinus contorta were fastest (1.16 ±0.67 mm.year-1; mean ± standard deviation), followed by Pseudotsuga menziesii (0.84 ±0.74 mm.year-1) and Picea (0.73 ±0.55 mm.year-1). Initial growth rates for all species were faster at sites with high-severity fires that initiated as single cohorts compared to sites with lower-severity fires indicated by scars (Mann-Whitney U = 22167, p ≤0.001). After high-severity fires, Pinus contorta had wide rings closest to the pith (1.40 ±0.83 mm.year-1) and initial growth rates were twice as fast as the average growth rate over their lifespan (relative growth = 2.17 ±1.12). After lower-severity fires the rings closest to the pith were not as wide (1.08 ±0.59 mm.year-1; Mann-Whitney U = 1420.5, p = 0.019) and relative growth was not as rapid (1.62 ±0.70; Mann-Whitney U = 1364, p = 0.009). Pseudotsuga menziesii and Picea had wider rings closest to the pith (1.09 ±0.79 and 0.90 ±0.64 mm.year-1, respectively) after high-severity fires compared to lower-severity fires (0.57 ±0.57 and 0.62 ±0.43 mm.year-1, respectively) (Mann-Whitney U = 327.5, p ≤0.001 and Mann-Whitney U = 20628, p ≤0.001, respectively). Moreover, Pseudotsuga menziesii and Picea relative growth was more rapid after high-severity fires (1.15 ±0.54 and 0.99 ±0.57, respectively), compared to lower-severity fires (0.76 ±0.37 and 0.89 ±0.51, respectively), with a statistically significant difference for Pseudotsuga menziesii (Mann-Whitney U = 422, p ≤0.009).  39  Age-structure continuity was the strongest indicator of mixed-severity fire history, whereas size-structure diversity indices were weak indicators of fire history class (Fig. 2.6). There were several indications age structure was more complex at sites with mixed- versus high-severity fire history, although only continuity was statistically significant. The age structures of mixed-severity sites were more discontinuous than the high-severity sites (Mann-Whitney U = 50, p = 0.03). Age structures tended to be more uneven and diverse at the mixed-severity sites; however, large variation overlapped with values from the high-severity sites. Size structure was a weaker indicator of fire severity.  Although medians indicated discontinuous, uneven and diverse sizes at sites with mixed- versus high-severity fire histories, differences were not significant due to large variation within and between fire-history classes.  2.4.5 Successional trajectories For all sites combined, Picea was most abundant in the canopy, followed by Pinus contorta and Pseudotsuga menziesii, regardless of fire history class (Fig. 2.7).  The mean importance values of canopy trees were more even at mixed- than high-severity fire history sites, although the mean importance value of Pseudotsuga menziesii was greater at the mixed-severity sites. Picea dominated the subcanopies, with its greatest mean importance value at high-severity sites. Among fire-history classes and canopy layers, the canopies of mixed- and high-severity sites were most similar (Fig. 2.8). The greatest differences were between the canopy and subcanopy layers at high-severity sites and between the canopy at mixed-severity sites and the subcanopy at high-severity sites.  40  2.5 Discussion 2.5.1 Frequency and severity of historic fires In the montane forests of Jasper National Park historical fires burned at a wide range of frequencies and severities at site and study-area scales. Fire scars caused by lower-severity surface fires were found at 20 of 29 sites. Fire scars were most common on Pinus contorta, followed by Pseudotsuga menziesii. Most Pinus contorta had only one scar likely caused by lower-severity fires, as high-severity fires would have killed the trees given their relatively thin-bark (Agee 1993). Multiple fire scars on thick-barked Pseudotsuga menziesii indicated two to five surface fires through time at 11 sites. At these sites, fire-to-fire intervals were variable (27-165 years) but most were 40-60 years. These intervals were similar to those in the nearby Foothills ecoregion (Amoroso et al. 2011) and mixed-conifer forests in southeastern British Columbia (Cochrane 2007; DaSilva 2009; Nesbitt 2010; Greene 2012; Marcoux et al. 2013), but longer than fire return intervals reported for the mixed-conifer forests in drier climates further south in western North America (Fulé et al. 2003; Beaty and Taylor 2008; Bekker and Taylor 2010).   The multiple techniques I used to interpret fire history provided evidence that low- to high-severity fires historically affected individual sites and the fire regime at the study-area scale was of mixed-severity. Fire-scarred trees combined with single or multiple post-fire cohorts were legacies indicating past fires of a range of severities through time at 18 of 29 sites. At two sites with ≥2 fire-scar years, high densities of veteran trees and low post-fire recruitment suggested the most recent fires were low-severity surface fires (Sherriff and Veblen 2006). At four other sites, the absence of veteran trees and the dominance of a single post-fire cohort suggested the 41  most recent fire was of high severity. However, the fire-scar records at each of these sites indicated ≥2 distinct surface fires prior to the most recent fire so they were classified as having a mixed-severity fire history (Heyerdahl et al. 2012). Of the 12 other mixed-severity sites which included at least one cohort and veterans, 3 had low densities of veteran trees and high post-fire recruitment suggesting the most recent fire was of high severity. The remaining nine sites had intermediate densities of veteran canopy trees and intermediate post-fire recruitment suggesting the most recent fire was of moderate severity. I found evidence of only past high-severity fires at 11 sites supporting my interpretation that the study area historically had a mixed-severity fire regime in which high-severity fires were common.  2.5.2 Changes to the fire regime during the 20th century The scars and cohorts I crossdated indicated the historic fire frequency varied at the study-area scale. Fire frequency was greatest from the 1870s to 1905, potentially caused by human use of fire by First Nation peoples, European peoples, or peoples of mixed ancestry during settlement (MacLaren 2007; Murphy et al. 2007). The fire records of 15 sites began prior to 1800 and included only six fires between 1646 and 1800. Lack of fire scars could indicate few fires burned or fire evidence may be lacking. Lack of fire evidence could be due to the young age of trees at many sites which limits the number of recorders and further in the past successive fires, mechanical damage and wood decomposition remove recorders and evidence of past fires (Van Pelt and Swetnam 1990; Parsons et al. 2007; Swetnam et al. 2011). I found no fire scars that formed after 1905 in the study area, although this is the period during which the sample depth and potential to record fires is greatest. This finding is unprecedented in 250 years.  42  The lack of fire scars during most of the 20th century may be attributed to fire exclusion and suppression. Jasper became a national park in 1907 and in 1910 local families were displaced from their homesteads which removed the application of fire as a land management method (MacLaren 2007; Murphy et al. 2007). Fire protection and suppression were implemented in the Park from 1913 onwards (Tande 1979; Kay and White 1995; Taylor 1998; Rhemtulla et al 2002; Van Wagner et al. 2006; MacLaren 2007; Murphy et al. 2007).  Changes in fire frequency in the Canadian boreal forests and some Cordilleran forests have been attributed to a long-term regional climatic shift to cooler and wetter conditions since the end of the Little Ice Age (Johnson and Larsen 1991; Flannigan et al. 1998). Although inter-annual to decadal variations in climate have been associated with fire occurrence in JNP (Schoennagel et al. 2005), there is little evidence weather and climate have been unsuitable for fire throughout the 20th century. Tree-ring reconstructions of precipitation in JNP do not support the argument of a climatic shift to persistent wetter conditions since the turn of the last century (Luckman 1998; Watson and Luckman 2001, 2004). Moreover, research on the occurrence of fires of lightning origin, lightning strikes and ignitions do not support changes in lightning fire occurrence in the Canadian national parks in the Rocky Mountains (White 1985; Wierzchowski et al. 2002). Since 1880, lightning-ignited fires >40 ha have been recorded in Banff National Park (BNP), which is 6,641 km2 in size and immediately south of JNP. Three fires ignited between 1880 and 1940 and four ignited between 1940 and 1980 (White 1985). My post-hoc analysis of the fire records for JNP (Parks Canada 2013), which is 10,878 km2 in size, shows 101 lightning-ignitions since 1940, only eight of which resulted in fires >40 ha in size. Given the differences in the size of the two Parks, the numbers of large lightning-ignited fires between 43  BNP and JNP are comparable. At the regional scale, relatively few lightning-ignited fires >40 ha occurred over the past century. White (1985) determined the lack of fires in BNP was due fire suppression. Since JNP is an adjacent landscape to BNP and the same fire management policy was applied to both Parks, the coincidence of the fire exclusion and suppression policy at the onset of the 20th century was likely an important factor which led to the lack of fires in the study area.  2.5.3 Forest dynamics and influence of the historical fire regime. 2.5.3.1 Stand Dynamics At the stand level, historic fires of different severity promoted compositional and structural diversity; however, differences between stands with mixed- versus high-severity fire histories in JNP were subtle. On average, importance values of canopy trees were more even among species and greater for Pseudotsuga menziesii at sites with mixed-severity fire histories. Presence of veteran trees and discontinuous age structures also distinguished mixed-severity sites; however, the evidence was revealed by dendrochronological reconstructions. Combined, these attributes were indicators of mixed-severity fire histories, as documented in other forests of the Canadian Cordillera (Heyerdahl et al. 2012; Marcoux et al. 2013). Nonetheless, these attributes were neither exclusive to nor present at all mixed-severity sites.  Similarities in forest composition and structure among sites with mixed- versus high-severity fire histories reflected the overriding effects of high-severity fires that burned ca. 107 to 123 years ago (Table 2.2). The last fire to burn at 18 sites was classified as high severity. Stand age structures at 24 sites were dominated by post-fire cohorts in which Pinus contorta, Picea and 44  Pseudotsuga menziesii formed the canopy whereas subcanopies were strongly dominated by Picea.  In JNP, Pinus contorta, Picea and Pseudotsuga menziesii established simultaneously following historic low- to high-severity fires; however, species-specific growth rates and adaptations to shade and fire resulted in size stratification among trees and canopy layers. Of the three species, Pinus contorta is shade-intolerant (Burns and Honkala 1990; Klinka et al. 2002). Since fire opens its serotinous cones facilitating seedling establishment immediately following fire (Burns and Honkala 1990; Klinka et al. 2002), Pinus contorta had the shortest regeneration lags and formed distinct cohorts (Antos and Parish 2002; Amoroso et al. 2011). It had the fastest initial growth rates, whether it established after lower- or high-severity fires, thus allowing lodgepole to dominate or co-dominate the canopy at many sites.  Picea is shade-tolerant but does not require shade or protection to establish (Burns and Honkala 1990; Klinka et al. 2002) and regenerated immediately following fire and after long lags since fire. Post-fire regeneration lags result from relatively slow seed dispersal by wind over distances >300m from surrounding forests or island remnants that survive fire (Dobbs 1976; Burns and Honkala 1990; Greene and Johnson 2000). Among trees establishing after fire, Picea growth rates were variable; however, its initial growth rates were slow compared to Pinus contorta and Pseudotsuga menziesii. Some trees grew to large diameters and dominated the canopy layer, while slow-growing individuals dominated the subcanopy at most study sites. Given its shade tolerance, Picea can regenerate beneath an existing canopy (Burns and Honkala 1990; Klinka et al 2002) and form secondary cohorts as stands develop. Among my study sites, 45  subcanopy Picea formed a cohort that was younger than the canopy trees only at site 11; however, at 19 sites, Picea saplings accounted for the majority of the regeneration (93 ±13%).  The regeneration dynamics of Pseudotsuga menziesii were variable among sites. Mature and thick-barked veterans that resisted and survived surface fires would provide a viable seed source both immediately following fire and over longer periods (Arno and Fiedler 2005). Pseudotsuga menziesii germinates well on mineral soil exposed by fire; however, it is intermediate in shade tolerance and can establish beneath an existing canopy (Burns and Honkala 1990; Klinka et al 2002). Pseudotsuga menziesii had intermediate initial growth rates. Like Picea, some Pseudotsuga menziesii established immediately following fire and grew rapidly into the canopy, while others regenerated after longer lags or grew more slowly particularly after lower-severity fires. Lower-severity fires likely resulted in smaller openings and more competitive growing conditions due to veteran trees, which would favour regeneration of shade-tolerant Pseudotsuga menziesii and Picea more than shade-intolerant Pinus contorta. Pseudotsuga menziesii establishment peaked 16 to 30 years after high-severity fires. The cause of the lag could be slow colonization following fire or slow initial growth rates. Slow growing trees take longer to grow to coring height (30cm) and the age corrections that we applied may have under-estimated the number of rings formed below coring height (Gutsell and Johnson 2002).  2.5.3.2 Impacts of Fire Exclusion on Successional Trajectories In some forests with historic mixed-severity fire regimes, within-stand comparisons of the species composition of the subcanopy relative to the canopy has been used as an indicator of 46  successional trajectories resulting from fire exclusion (Taylor and Solem 2001; Beaty and Taylor 2008). This approach assumes (1) subcanopy trees are younger than canopy trees and represent future canopy trees and (2) succession will proceed in absence of stand-level disturbances (White et al. 1985; Oliver and Larson 1996). This approach has been successfully applied in forests where fire exclusion has promoted stands to the mature or old-growth stages of stand development (Bekker and Taylor 2010; Scholl and Taylor 2010). In these forests, shade-tolerant trees have regenerated beneath the canopy and are recruiting in gaps as canopy trees die. Moreover, structures in these forests include dense subcanopies and ladder fuels with regenerating trees which are often thin-barked and less resistant to lower-severity fires (Fulé et al. 2003; Perry et al. 2011). Combined, these changes result in forests that are less resistant to lower-severity fires and more prone to high-severity crown fires (Littell et al. 2010).  In JNP, forest canopies were mixed in composition and subcanopies were dominated by shade-tolerant Picea, regardless of fire history classes. However, the subcanopy trees were similar in age as the canopy trees, except at site 11. Trees in both strata had originated after high-severity fires with both composition and structure of the forest canopy reflecting the stem-exclusion stage of stand development. The subcanopy trees were slow-growing, shade-tolerant Picea, rather than a recently-established cohort resulting from understory reinitiation. For the current subcanopy Picea to form the canopy in future, they will need to outlive current canopy trees and recruit in gaps formed as canopy trees die.  Based on the average time between fires found here I would have expected up to five surface fires among the 29 study sites in the absence of 20th Century fire exclusion. My fire-scar 47  record showed 13 fire years between 1646 and 1905, averaging one fire every 20 years. Some of the historic fires burned and scarred trees at multiple sites. Since 1905, up to five fire events may have been missed, some of which may have burned multiple sites, had fires continued to burn rather than being suppressed. Such disturbances would have led to more diverse size and age structures and possibly species composition among my study sites. Periodic lower-severity fires would have increased stand-level diversity (Agee 1993) by reducing the number of thin-barked Picea in the subcanopy and created canopy openings and substrates suitable for Pinus contorta and Pseudotsuga menziesii regeneration, in addition to Picea (Burns and Honkala 1990; Amoroso et al. 2011). High-severity fires would have diversified the ages and stages of development among stands (Agee 1993). Instead, in absence of fire, all stands have developed similarly. At most sites, the canopy was closed, subcanopy Picea formed ladder fuels and mostly shade-tolerant regeneration was in the sapling strata.   My reconstructions of stand-level dynamics for individual sites are consistent with the consequences of fire exclusion documented at the landscape level in JNP (Rhemtulla et al. 2002).  Photographs taken in 1915 of the montane and subalpine ecoregions in JNP (Bridgland 1924) revealed a landscape with young age structures at the stand-initiation stage (Rhemtulla et al. 2002). In the montane ecoregion, five vegetation types dominated alongside non-vegetative cover (water, wetland, sand-gravel, rock and anthropogenic): closed-canopy forest (16-70% crown closure) represented 35% of total cover, open forest (<16% crown closure) 16%, shrub 13%, forb-grassland 11% and juvenile forest (sapling stage) 7% (Rhemtulla et al. 2002). This variability in vegetation cover type is consistent with my fire records indicating 30 even-aged cohorts were <20 to ca. 100 years old in 1915 and recent surface fires causing scars were found 48  at 20 sites. In 1997 the same areas in the montane ecoregion were photographed (Rhemtulla et al. 2002). Of the total cover in 1997, 65% was dominated by forests with 51-100% crown closure indicating a decrease in landscape heterogeneity (Rhemtulla et al. 2002). This landscape-level change can be explained by the lack of fires in the study area since 1905, which allowed individual stands throughout the landscape to develop to the stem-exclusion and understory re-initiation stages.  2.6 Conclusion In the montane ecoregion of Jasper National Park, low- to high-severity fires historically affected individual sites and the fire regime at the study-area scale was of mixed-severity. Site level fire histories reconstructed from fire scars and cohorts indicated 18 sites were of mixed-severity whereas 11 were of high-severity. Differences between stands with mixed- versus high-severity fire histories in JNP were subtle. Key differences distinguishing mixed-severity sites were importance values of canopy trees which were more even among coniferous species and greater for Pseudotsuga menziesii, the presence of veteran trees, and discontinuous age structures. Current stand composition and age structures reflected the effects of higher-severity fires that burned ca. 100 years ago at 24 of 29 sites, followed by an absence of fire since 1905. Canopy composition varied among sites; however, subcanopies were strongly dominated by shade-tolerant and fire-intolerant Picea, regardless of fire history severity class. In the absence of fires of a range of severities during the 20th century, individual stands have developed similarly, resulting in a decrease of landscape heterogeneity.   49     Tree Density (ha-1)Live (Dead) Canopy Trees Live (Dead) Subcanopy TreesDeciduous Deciduous765 - - - 786 (314) - 472 -- - 142 (16) - 191 - 382 (64) -29 29 229 - 59 - 118 -- 197 - - - 334 334 -70 - 56 (14) - - - 793 (227) 113(62) - 218 31 (361) 180 1083 -1973 - - - - - - -852 95 - - - - - -- - 352 88 - - 340 113 (113)97 (16) - 49 - 736 (589) - 147 -527 (226) - - - 91 (274) 91 457 -- 38 (154) 192 (38) - - 168 126 (126) -- 192 (38) 38 (154) - - 212 106 (35) -26 79 26 - - 457 366 183- - 127 (14) - - - 441 -- - 180 - - - 1273 -- 74 (37) 258 - - - 58 (29) 87 (115)236 79 79 - 127 (127) - 509 (382) 127- 118 (29) 147 - - - 577 (577) -65 130 455 - - - 3108 -70 52 52 - 4212 - 1805 -- 18 144 (18) - - - 2981 (331) -54 54 272 (163) - - - 274 (640) -99 (33) 166 33 - - 588 392 -170 - 113 - (271) 271 406 135 (271)106 159 265 - 107 - 429 -379 126 126 - 185 - 1663 -23 93 116 - 102 - 508 (406) -42 (14) 14 71 - 757 (189) - - -25Density of Regeneration (%)Live SaplingsP. contorta P. menziesii Picea Picea PiceaP. menziesii P. menziesiiP. contorta P. contorta- 100----- 100- 100100100- - 10010010075- -- - ---------50 50- 332067- - 100100- -100 --- -- ---- -- ------100- - 10054- 95- 96- - 100- 10010014 29 57- 10080100 - -ElevationTransect no.Site (m.a.s.l.)SlopeAngle(degrees)SlopeAspect(degrees)I 1 1029 0 3152 1024 0 3333 1024 0 34 1024 0 27II 5 1038 0 1436 1002 0 907 990 0 268 1031 17 57III 9 1010 3 12010 1063 8 12811 1116 7 87IV 12 1040 7 8513 1062 8 2914 1112 33 96V 15 1039 3 9716 1060 5 12217 1100 9 18318 1155 29 123VI 19 1147 22 35820 1268 32 33221 1411 21 335VII 22 1083 19 30923 1126 10 34024 1186 15 23025 1195 10 240VIII 26 1153 36 36027 1214 38 2428 1425 26 32729 1570 8 18Table 2.1 Site attributes and species composition of the 29 study sites in the montane forests of Jasper National Park. Density (ha-1) and basal area (m2 ha-1) of living and dead trees are given for the dominant conifers (Pinus contorta, Pseudotsuga menziesii and Picea) and deciduous trees (Populus tremuloides and Populus balsamifera combined). Regeneration is the relative abundance of live conifer saplings.  50  Table 2.1 (continued).       SiteI 1234II 5678III 91011IV 121314V 15161718VI 192021VII 22232425VIII 26272829Basal Area (m2.ha-1)Live (Dead) Canopy Trees Live (Dead) Subcanopy TreesDeciduousP. contortaTransect no.P. menziesii Picea P. contorta P. menziesii Picea Deciduous22 - - - 12 (2) - 2 -- - 11 (2) - 4 - 17 (2) -1 2 9 - 1 (0.1) - 1 -- 17 - - - 7 4 -6 - 4 (2) - - - 8 (2) 2(5) - 10 3 2 (7) 2 14 -38 - - - - - - -16 7 - - - - - -- - 44 5 - - 8 12 (3)9 (1) - 9 - 31 (18) - 6 -15 (5) - - - 1 (4) 0.3 3 -- 6 (22) 10 (3) - - 5 2 (2) -- 14 (11) 3 (17) - - 4 1 (0.4) -6 14 2 - - 2 4 5- - 6 (1) - - - 11 -- - 12 - - - 18 -- 4 (3) 15 - - - 1 (1) 2 (1)12 10 5 - 4 (7) - 8 (7) 3- 11 (3) 5 - - - 2 (8) -2 9 12 - - - 33 -2 3 3 - 39 - 6 -- 2 5 (1) - - - 17 (5) -3 4 32 (8) - - - 6 (13) -7 (2) 16 4 - - 13 4 -13 - 15 - (5) 5 2 3 (5)3 7 6 - 1 - 5 -9 7 5 - 3 - 11 -1 4 6 - 0.2 - 2 (7) -3 (1) 1 3 - 8 (1) - - -51  Table 2.2 Fire record for the 29 study sites in the montane forests of Jasper National Park.   no.52    Figure 2.1 Fire history study area in Jasper National Park (top). The 29 fire-history sites in the Athabasca River valley, 15 km north of Jasper townsite (bottom). 0 2 4 km 118°5’WAthabasca RiverJasper Lake118°0’W1700m1500m1300m1100m1100m1300m1210876Town ofJasper1229282726192021252423221718161513141195430 25 kmJasper NationalPark boundaryRivers & lakesMontane ecoregionStudy areaGrid NorthJasperTown ofJasperNationalPark53°5’NJacques RangeColin Range53   Figure 2.2 Size-structure histograms of trees (dbh ≥5 cm) by species for the 29 fire-history sites located along eight transects (rows). Histograms include all live and dead trees (n = 20) sampled per site. Species are Pinus contorta (black), Pseudotsuga menziesii (grey), Picea (white), Populus tremuloides (diagonal crosshatch) and Populus balsamifera (vertical crosshatch). Frequency (number of trees)Diameter (upper limit of 5-cm bins)121513 141619 2022 2395162 32710 117 8211725282418405100510051005100510051005105 15 25 35 45 55 65295 15 25 35 45 55 650510 265 15 25 35 45 55 65 5 15 25 35 45 55 6554   Figure 2.3 Age-structure histograms of trees (dbh ≥5 cm) by species for the 29 fire-history sites located along eight transects (rows). Histograms include all live and dead trees sampled per site. Fire-scar years are represented by black triangles and the beginning of an even-aged cohort by white triangles. Species are Pinus contorta (black), Pseudotsuga menziesii (grey), Picea (white) and Populus tremuloides (diagonal crosshatch).  Frequency (number of trees)Year of establishment (upper limit of 15-year bins in calendar years)5 (n = 17)01020 6 (n = 19)1 (n = 20)01020 2 (n = 20)9 (n = 14)01020 10 (n = 18)12 (n = 17)01020 13 (n = 19)15 (n = 18)01020 16 (n = 20)19 (n = 17)01020 20 (n = 20)22 (n = 19)01020 23 (n = 20)26 (n = 20)1550 1850 200001020 27 (n = 20)1550 1700 1850 20008 (n = 10)4 (n = 19)18 (n = 20)25 (n = 17)29 (n = 19)1550 1700 1850 20007 (n = 9)3 (n = 20)11 (n = 20)14 (n = 18)17 (n = 20)21 (n = 20)24 (n = 19)28 (n = 19)1550 1700 1850 2000170055      Figure 2.4 Fire history from 1550 to 2012 at all 29 sites. Horizontal lines represent the site-level composite tree-ring records (top to bottom: sites 1 to 29). The length of each line represents the period of record, starting from the pith of the oldest tree to 2012. Fire evidence includes crossdated, annually-resolved fire scars (black triangles) and the year establishment of the oldest tree in post-fire cohorts (white triangles). For sites lacking fire scars, dashed lines indicate the length of the record. The bottom graph shows the number of sites with fire scars (black line) and the number of sites recording a fire (grey bars) over time. 56       Figure 2.5 Species-specific lags in tree establishment following (a) predominantly less severe fires causing scars (left column) and (b) high-severity fires initiating cohorts only (right column).    RelativefrequencyLag in establishment (years)1-1516-3031-4546-6061-7576-9091-105106-12004080 Picea (n = 133)04080 Pseudotsuga menziesii (n = 35)04080 Pinus contorta (n = 38)1-1516-3031-4546-6061-7576-9091-105106-12004080 Picea (n = 135)04080 Pinus contorta (n = 101)04080 Pseudotsuga menziesii (n = 44)(b) Post-fire cohorts(a) Fire scars57   Figure 2.6 Comparison of age- and size-structure continuity (top), evenness (middle) and diversity (bottom) between fire severity classes (Marcoux et al. 2013). In each box plot, the black horizontal line represents the median and box boundaries are the 25th and 75th percentiles; and bars are the 10th and 90th percentiles. 0510152025Continuity index0510152025ContinuousDiscontinuous0.00.20.40.60.81.01.21.4Shannon diversity index0.00.20.40.60.81.01.21.4HighMixedHighMixedUniformDiverseAge Structure Size Structure024681012024681012Evenness indexEvenUneven58   Figure 2.7 Mean and standard errors of importance values by coniferous species and deciduous trees according to fire history class (columns) and canopy layer (rows).     P. contortaP. menziesiiPiceaDeciduous treesMeanimportancevalueofsubcanopy trees050100150200P. contortaP. menziesiiPiceaDeciduous trees050100150200Mixed-severity (n = 18) High-severity (n = 11)Meanimportancevalueofcanopy trees59   Figure 2.8 Mahalanobis distances between canopy and fire history classes. Shorter (longer) distances imply greater similarity (difference) between classes.   Canopy &high-severity fireCanopy &high-severity fireCanopy &mixed-severity fireSubcanopy &high-severity fireSubcanopy &high-severity fireSubcanopy &high-severity fireCanopy &mixed-severity fireSubcanopy &mixed-severity fireSubcanopy &mixed-severity fireSubcanopy &mixed-severity fireCanopy &high-severity fireCanopy &mixed-severity fire0.080.260.410.471.381.6860  Chapter 3: Temporal Climate-Fire Relations  3.1 Introduction Fire regimes in western North America are anticipated, based on climate-change projections, to include wildfires of increasing number, size and severity, with measureable effects already observed in some subalpine and boreal forests (Flannigan et al. 2003; McKenzie et al. 2004; Westerling et al. 2006). Apart from climate, fire regimes can also be influenced by land use and fire management (Agee 1993); however, these effects vary among forests (Schoennagel et al. 2004; Meyn et al. 2007). Understanding the relative importance of climate and humans and their interacting effects on fire regimes is important for developing effective management plans in response to climate change.  At regional scales, weather and climate are drivers of fire occurrence and regimes, respectively (Cyr et al. 2007). Weather influences fire occurrence and behaviour (Agee 1993). Low relative humidity, warm temperatures and strong winds decrease fuel moisture, whereas precipitation increases it (Agee 1993; Fauria et al. 2011). Combined, these weather attributes affect fuel combustibility, probability of ignition, and fire spread, intensity and severity (Taylor et al. 1996; Fauria et al. 2011). Climate influences fire at a range of temporal scales (Falk et al. 2007). Within years, seasonal variation in temperature and precipitation determine the timing and length of the fire season (Agee 1993; Meyn et al. 2007). At inter-annual to multi-decadal scales, variation in climate determines the frequency of droughts conducive to fire or of wet intervals hindering fire (Johnson et al. 1999; Bergeron et al. 2000; Grissino-Mayer and Swetnam 2000; Heyerdahl et al. 2002; Hessburg et al. 2005; Schoennagel et al. 2005; Taylor and Beaty 2005). 61  Long-term climatic variation can influence fire frequency within fire regimes (Veblen et al. 2000; Dale et al. 2001; Morgan et al. 2001; Whitlock et al. 2003).  The effects of climatic variation on fire regimes vary among forest types (Schoennagel et al. 2004; Meyn et al. 2007). In warm dry climates, such as in ponderosa pine (Pinus ponderosa Douglas ex C. Lawson) forests in the southwest United States of America (USA), historic fires burned frequently (Swetnam and Betancourt 1990; Swetnam 1993). In these forests, fuels are sufficiently desiccated by warm, dry weather each fire season; however, fuel availability is limiting (Schoennagel et al. 2004; Meyn et al. 2007). Fine and ladder fuel accumulation limits fire spread (Fulé et al. 1997; Hessburg et al. 2005; Heyerdahl et al. 2006) and short periods of above-average moisture conditions can enhance fuel production and thereby remove the limitation in fuel availability (Baisan and Swetnam 1990; Grissino-Mayer and Swetnam 2000). In contrast, subalpine and boreal forests grow in cool, humid climates in which fires burn less frequently and are limited by fuel combustibility (Payette 1992; Turner and Romme 1994; Agee 1997; Buechling and Baker 2004; Schoennagel et al. 2004; Podur and Martell 2009).   A significant drying period is necessary for fuel combustion (Agee 1993; Fauria et al. 2011). In the long periods between fires, fuels accumulate (Veblen 2000; Schoennagel et al. 2004) then burn during unusual droughts (Johnson and Wowchuck 1993; Bessie and Johnson 1995; Sibold and Veblen 2000; Stocks et al. 2002; Buechling and Baker 2004). In montane mixed-conifer forests, topographic variation creates complex moisture gradients (Agee 1998). Fuel availability and combustibility are less limiting than in ponderosa pine forests in the 62  southwest USA and subalpine or boreal forests, respectively. As a result, fires burn with a mix of frequencies (Taylor and Skinner 1998; Hessburg et al. 2005; Marcoux et al. 2013).  Wildfire ignitions are predominantly from lightning or humans (Agee 1993; Fauria et al. 2011). Historically, in North America, First Nation peoples used fire as a management tool to grow food, facilitate foraging and hunting, clear vegetation for travel and to reduce wildfire hazards around communities (Lewis 1985; Bahre 1991; Agee 1993; Kay 1995; Murphy et al. 2007; Miller 2010). Contemporary fire records in Canada indicate about 55% of fires are ignited by people either intentionally (e.g., prescribed burns or arson) or accidentally (Government of Canada 2013).   However, the levels of secondary human impacts on fire such as fire exclusion and suppression have been debated for different forested landscapes in western North America (Schoennagel et al. 2004). Fire exclusion is the indirect reduction in fire due to land use and cover changes (Covington and Moore 1994a, 1994b; Veblen et al. 2000), whereas fire suppression is the direct reduction in fire due to preventative measures, initial attack and the management of large fires (Martell 2001; Arienti et al. 2006). Fire exclusion and suppression can alter fire regimes by reducing fire frequency which potentially affects severity (Agee 1993; Schoennagel et al. 2004). In dry forests with historically short fire return intervals, impacts of fire suppression can be measured within decades (Swetnam et al. 1999). In the absence of frequent surface fires, forest structure and fuels change relatively quickly (Schoennagel et al. 2004). Conversely, in mesic forests with historically long fire intervals, impacts of fire 63  suppression require longer periods to have measurable effects (Turner et al. 2003; Schoennagel et al. 2004).  In the Canadian Cordillera, boreal Canada and elsewhere, the decrease in fire frequency during the 20th century has been attributed to fire exclusion and suppression and the fire regime is considered outside its historical range and variability (Swetnam et al. 1999; Kipfmueller and Baker 2000; Taylor and Skinner 2003; Veblen 2003; Amoroso et al. 2011). However, debates have been raised about the pervasiveness of the reduced fire frequency and its impact on forest structure and composition (Veblen 2003; Schoennagel et al. 2004). Reduced fire frequency in boreal forests has been attributed to cooler and wetter climate since the end of the Little Ice Age (Johnson and Larsen 1991; Johnson 1992; Bergeron and Archambault 1993). These studies assume fire suppression has had no significant effects on the fire regime (Romme and Despain 1989; Nash and Johnson 1996; Johnson et al. 1998, 2001). However, recent compelling evidence shows fire suppression has significantly impacted fire regimes in some subalpine and boreal forests (Cumming 2000; Kipfmueller and Baker 2000; Podur and Martell 2009).   Jasper National Park (JNP) is located at the transition between Cordilleran and Boreal ecozones in the Rocky Mountains of Alberta, Canada (Peet 2000). Within the Park, steep environmental gradients creates shifts from grasslands to subalpine forests over short distances (Holland and Coen 1982). Fire regimes also vary over short distances with a mixed-severity fire regime in montane forests (Chapter 2) and high-severity fires in the subalpine forests (Peet 2000). Documented changes to the fire regime in the 20th century include decreased fire occurrence (Chapter 2), increased forest cover (Rhemtulla et al. 2002) and shifts to closed-64  canopy late-successional vegetation cover at stand (Chapter 2) and landscape scales (Rhemtulla et al. 2002). Whether these changes were caused by climatic change, human impacts or both, remains undetermined. There is abundant evidence people of different cultures have historically influenced the fire regime in the montane forests of JNP, including active fire suppression after 1913 (Tande 1979; Kay and White 1995; Taylor 1998; Rhemtulla et al 2002; Van Wagner et al. 2006; MacLaren 2007; Murphy et al. 2007). Past research determined the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) had a significant influence on precipitation and historic fire regimes in JNP (Schoennagel et al. 2005). However, the climate-fire analysis was based on a fire record that was not crossdated (Tande 1977, 1979) and errors have been identified in it (L. Daniels, personal communication, July 2012).  In this study I examined the role of climatic variation as a driver of the fire regime in montane forests of JNP. I tested two inter-related hypotheses. (1) Historic fire occurrence depended on inter-annual to decadal variation in climate. (2) Climatic variation explains the absence of fire within my study area in JNP during the 20th century. To represent the landscape, I crossdated fire scars and tree ages at 172 sites in a 3,300 ha study area distributed east (1,900 ha) and west (1,400 ha) of the Athabasca River valley. To allow comparison with other studies in montane forests of western North America, I quantified the effects of drought, the ENSO, PDO and Atlantic Multidecadal Oscillation (AMO) on fire occurrence using crossdated fire records. I combined these results with the well-documented land-use history of JNP to understand the relative importance of climate and human impacts on the historic and contemporary fire regime. My research contributes to knowledge of the drivers of historical fire regimes, which can be used 65  to enhance scientifically-based conservation and fire management in JNP, as well as sustainable forest management practices in similar forests surrounding the Park.  3.2 Materials and Methods 3.2.1 Research design This research builds on a study conducted from 1997 to 2000 as collaboration between the Foothills Research Institute and Jasper National Park (Rogeau 1999; D. Andison, personal communication October 2011). The original goal of the study was to construct a time-since-fire map depicting forest patches of different ages that established after different fires through time (Johnson and Van Wagner 1985). Sampling was carried out in discrete patches of forests identified on air photos (Heinselman 1973; Johnson et al. 1990) and at forest edges between forest patches where fire-scars may occur (Johnson and Gutsell 1994). Patches of forest were sampled along 37 transects. Transects were distributed on both sides of the Athabasca River, 24 west of the Athabasca River and north of the Snaring River and 13 east of the Athabasca River and north of Colin Range. On each transect two to nine sites were sampled. Transects started at the valley bottom in the montane forest and extended upslope into the subalpine forests. Distance between sites averaged 340 m (range = 50 to 1035 m).  3.2.2 Field sampling At each of the 172 sites, a centre-point tree was selected around which a circular plot with a 20 m radius was searched for fire-scarred trees, snags, stumps and logs (hereafter “scarred trees”). At each site, a full cross-section was sampled from up to six scarred trees (n = 104). Up to eight live trees representing different coniferous species, size and height classes were sampled 66  within 20 m of each centre-point tree (n = 825). For each sampled tree, the distance from the centre-point, species, diameter at breast height (dbh) and canopy layer was recorded. The age of trees was estimated using increment cores taken ca. 30 cm from the ground and aimed to include the pith. At a subset of 29 sites, I conducted detailed fire history reconstruction through time using the methods in Chapter 2.  3.2.3 Laboratory analysis Fire-scar and core samples were mounted on wooden supports and all samples were sanded following standard protocols (Stokes and Smiley 1996). High-resolution (1200 or 2400 dots per inch) digital images were taken from the bark to the inner-most ring and, in the case of fire scars, along the radii that included the tips of fire scars. Using Coo-recorder (Larsson 2011a), I measured ring widths and using the programs CDendro (Larsson 2011b) and COFECHA (Grissino-Mayer 2001a), I visually crossdated and statistically verified the ring dates to determine the years of the inner-most and outer-most rings and individual fire scars (hereafter “fire-scar year”) (Grissino-Mayer 2001a). For 361 cores that missed the pith, I applied a correction to estimate the number of missed rings (Duncan 1989). I applied species-specific age-height corrections (Powell et al. 2009; Daniels unpublished data) to estimate the number of years for the trees to grow to sampling height.  3.2.4 Fire history I developed composite fire chronologies for individual sites that included fire-scar years. The length of each chronology was determined by the age of the oldest tree at the site, even if it was not scarred. Since the study area is dominated by fire-susceptible Picea and Pinus contorta 67  (Chapter 2), the oldest trees represented the period during which fires were likely to be recorded had the site burned. For 45 sites with fire scars, I determined the number of fires, mean, minimum and maximum fire intervals and time since last fire (TSLF).  Site-level fire chronologies were combined into composite fire chronologies for two locations west and east of the Athabasca River and for all sites in the study area combined. For each composite fire chronology, I determined the length of the fire record, the number of fires, mean, minimum and maximum fire intervals and TSLF. Using the composite fire record for the entire study area, years of widespread fire were years in which fire was recorded at >5 sites.  3.2.5 Local Pseudotsuga menziesii chronology as a proxy of drought Pseudotsuga menziesii is sensitive to drought and has been used to reconstruct precipitation in Jasper National Park (Watson and Luckman 2001, 2004, 2005). I acquired the original ring-width data for Pseudotsuga menziesii for the Pyramid and Patricia lake sites which are closest to my study area. The data included 36 series sampled by Ferguson and Parker (1965) and 43 series sampled by Watson and Luckman (2001). I combined the series with the crossdated ring-width series from 308 Pseudotsuga menziesii I sampled, to develop a regional chronology using the program COFECHA (Grissino-Mayer 2001a). I selected a subset of 81 cores that were highly correlated (inter-series correlations ≥0.663) and had no flagged segments.  I used ClimateWNA (Wang et al. 2012), a climate mapping system based on regression modelling, to derive climate records from 1901 to 2009 for the midpoint between Pyramid and Patricia lakes (interpolated location point: 52°54’ N, -118°05’ W, 1,182 m.a.s.l.). The climate 68  parameters were monthly total precipitation and monthly maximum and mean temperatures. Using the monthly climate records, I calculated monthly heat-moisture indices (after Wang et al. 2006; Chavardès et al. 2012): Heat-moisture indexmonthly = (Tmean + 10) / (P / 100) where, Tmean is the monthly mean temperature (°C) and P is monthly total precipitation (mm). Low moisture availability resulting from low precipitation and/or warm temperatures is indicated by high indices.  I conducted climate-growth analyses to verify Pseudotsuga menziesii radial growth is a suitable proxy for growing season drought in the study area. I used the program ARSTAN to detrend individual ring-width series and to derive a standard and residual chronology (Cook 1985; Cook and Holmes 1986). To account for the non-climatic, age-related trend in ring widths, a single detrending was applied by fitting a negative exponential curve or linear regression through each ring-width series. I compared climate-growth relationships between the resulting residual chronology and the modelled climate data using the program Dendroclim2002 (Biondi and Waikul 2004). Pearson’s correlation coefficients were calculated between ring-widths and each of the monthly climate variables (monthly total precipitation, maximum and mean temperature, and heat-moisture indices) (Biondi and Waikul 2004). To assess direct and lagged climate influences on tree growth, correlation coefficients were calculated for the 18-month window from the April prior to ring formation through September of the year the ring was formed (e.g., summer, fall and winter prior to ring formation plus spring and summer of the year of ring formation). Statistical significance was determined by bootstrapping (Biondi and Waikul 2004). 69   3.2.6 Climate-fire relations I used superposed epoch analysis (SEA) to determine the influence of inter-annual climatic variation on fire occurrence between 1646 and 1915 (Grissino-Mayer 2001b). SEA was used to test whether the 18 fire years I documented in Jasper National Park (JNP) occurred during anomalous climate conditions. To assess statistical significance, a bootstrapped Monte Carlo simulation randomly selects 1,000 years and calculates conditions associated with those years to define 95% and 99% confidence intervals (Grissino-Mayer 2001b). To represent climate, I used the residual Pseudotsuga menziesii chronology as a proxy of drought conditions (Watson and Luckman 2001, 2004, 2005), as well as tree-ring reconstructions of the El Niño-Southern Oscillation (ENSO) (Cook et al. 2008), Pacific Decadal Oscillation (PDO) (Gedalof and Smith 2001) and Atlantic Mutidecadal Oscillation (AMO) (Gray et al. 2004), the hypothesized drivers of drought in JNP (Schoennagel et al. 2005). Specifically, I tested whether mean values of climate indices were significantly different during fire years or during the four years preceding and two years following fires. I tested lagged effects to assess whether patterns of climate prior to a fire year exert any influence on a given fire (Grissino-Mayer 2001b). Climate does not influence a fire in years following that year; however, analyses which include the years following fire may reveal important multi-year climatic patterns associated with fire, such as ENSO phases (Grissino-Mayer 2001b).  To test potential drivers of drought I stratified multiple years and/or decades as (a) El Niño or non-El Niño phases (Garcia-Herrera et al. 2008; Yu and Kim 2013), (b) positive or negative PDO phases (Gedalof and Smith 2001) and (c) positive, neutral or negative AMO 70  phases (Gray et al. 2004). To assess the effects of prolonged drought, I stratified multiple years and decades as dry or wet phases based on the low-frequency analyses by Watson and Luckman (2004). I assessed their effects on fire occurrence between 1646 and 1915 using contingency tables. Each year was stratified as a fire or non-fire year based on my composite fire scar record for all sites. I calculated the proportion of fires occurring during different climatic phases separately. I also tested if potential drivers of drought interacted to amplify (same sign) or dampen (opposite sign) their effects on fire occurrence via two-way combinations (Schoennagel et al. 2005). Statistical significance was determined using χ2 goodness-of-fit tests (α = 0.05). The number of fires was too small to test three-way interactions among potential drivers.  3.2.7 Twentieth century climatic conditions and fire occurrence I determined if climatic conditions had been conducive to fire during the 20th century. First, I assessed climatic conditions associated with the historic fire record from 1646 to 2009. I used Pseudotsuga menziesii ring-widths as an indicator of drought because high temperatures, low precipitation and high heat-moisture indices during the growing season result in narrow rings. I used analysis of variance (ANOVA; SAS 9.3) and post hoc Tukey tests to compare mean ring-width indices during the 18 fire years versus periods of dry or wet climate from 1646 to 1915 as defined by Watson and Luckman (2004). To compare historic conditions with 20th century climate and to assess variation during the 20th century, I used ANOVA and post hoc Tukey tests to compare mean ring-width indices, annual (previous September to current August) maximum temperature, precipitation and heat-moisture indices during three periods from 1916 to 2009. Watson and Luckman (2004) reported a dry period, 1916 to 1947, followed by a wet 71  period, 1948 to 1982. I included an unclassified period from 1983 to 2009, which exceeded Watson and Luckman’s (2004) analysis.  3.3 Results 3.3.1 Fire history The 104 fire-scarred cross-sections recovered from 45 of 172 sites yielded 138 fire scars (Fig. 3.1 and 3.2). Among all sites, I found fires burned in 18 years from 1646 to 1915. Fire records for the 115 sites west of the Athabasca River averaged 181 ±79 years (range = 78 to 416 years) based on the age of the oldest tree at each site (Table 3.1). Twenty-five sites (22%) had fire scars, with up to five fire-scar years per site. At the ten sites with multiple fires, mean fire intervals ranged from 31 to 62 years. Time since last fire (TSLF) averaged 141 ±36 years (range = 107 to 273 years). The composite fire record included 11 fire-scar years at intervals of 19 to 121 years (Fig. 3.3a).   Fire records for the 57 sites east of the Athabasca River averaged 192 ±105 years (range = 86 to 533 years) based on the age of the oldest tree at each site (Table 3.2). Twenty sites (35%) had fire-scars, with up to three fire-scar years per site. At the eight sites with multiple fires, mean fire intervals ranged from 11 to 164 years. Time since last fire (TSLF) averaged 109 ±28 years (range = 83 to 193 years). The composite fire record included ten fire-scar years at intervals of 15 to 132 years (Fig. 3.3b).   For the entire study area, the return intervals for the 18 fires averaged 55 ±34 years (range = 15 to 132 years). Widespread fires in 1772, 1827, 1889 and 1905 scarred trees at 6, 10, 72  12 and 15 sites, respectively (Fig. 3.3c). A 54 year gap with no fire scars occurred between 1773 and 1826, inclusive, and no fire scars were recorded after 1915.  3.3.2 Pseudotsuga menziesii tree-rings as a proxy of drought The Pseudotsuga menziesii residual chronology was a strong indicator of drought (Fig. 3.4). The correlations between radial growth and monthly precipitation between 1902 and 2009 were predominantly positive. Correlations with previous year summer precipitation were consistently positive, with significant correlations for August and September. Correlations with current year precipitation were positive from May to September, except July, with significant correlations in May and June.  Correlations between radial growth and monthly maximum temperatures, mean temperatures and heat-moisture indices were predominantly negative (Fig. 3.4; mean temperature not shown). Correlations were significant for previous July to September heat-moisture indices and previous September maximum temperature. Correlations with current year May to September temperatures and heat-moisture indices were negative, except July heat-moisture indices. Correlations were significant in May and June for maximum temperature and heat-moisture indices.  3.3.3 Climate-fire relations Most fires burned during years when the ring-widths were narrower than one standard deviation below average (39%) (Fig. 3.5). Widespread fires only burned when ring-widths were narrower than average. Fires were associated with narrow ring-width indices in the residual 73  Pseudotsuga menziesii chronology (α = 0.01), indicating drought conditions during fire years (Fig. 3.6). Ring-width indices during antecedent or succeeding years were not significant. Annual values of the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) or the Atlantic Multidecadal Oscillation (AMO) indices did not have significant relationships with fire occurrence. The 18 fires between 1646 and 1915 burned during dry multiyear periods (p = 0.041) (Fig. 3.7a) and showed a weak association with El Niño phases during negative phases of the PDO (Fig. 3.7b,c,e) but no association with AMO phases (Fig. 3.7d,f,g). Overall, the power of the statistical tests was limited by the small number of fires over 270 years.  3.3.4 Fire occurrence and drought Mean ring-width indices were smallest, indicating drought, during the 18 fire years between 1646 and 1915 (Fig. 3.8). Relative to the fire years, the mean indices during dry periods and the unclassified period were not significantly different but the mean indices were significantly larger during wet periods. Variation among years within periods was large, indicating individual dry/wet years even during wet/dry periods. As a result of this variation, the mean ring-width indices during the dry and unclassified periods were not significantly different from the wet period during the 20th century.   The instrumental climatic records varied significantly between dry and wet periods during the 20th century and were consistent with the above interpretations using ring-widths as a proxy for drought (Fig. 3.9). Maximum temperature was significantly greater and annual precipitation and moisture availability were significantly lower during the dry periods relative to the wet periods. The unclassified period was intermediate; maximum temperature did not differ 74  significantly from the dry period but it was wetter. As a result, moisture availability did not differ significantly from the other two periods.  3.4 Discussion 3.4.1 Climatic variation and historic fires in Jasper National Park Historic fires burned during significant drought years; however, relations with the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) were less clear. Since my fire record included only 18 fires, the low sample size limited the statistical power to discern patterns between fire occurrence and inter-annual to decadal climate influences. Nevertheless, my findings that fires were weakly associated with El Niño events are consistent with other climate-fire studies in Jasper National Park (JNP), western Canada and the Pacific Northwest of the USA (Westerling and Swetnam 2003; Schoennagel et al. 2005; Heyerdahl et al. 2008). However, the observed association with the negative phase of the PDO contrasts other studies (Westerling and Swetnam 2003; Hessl et al. 2004; Gedalof et al. 2005; Kitzberger et al. 2007; Heyerdahl et al. 2008; Da Silva 2009). Below, I compare my findings with other studies in western North America to understand the observed spatial and temporal variation in climate-fire interactions.  The influences of ENSO vary with latitude and affect fire regimes differently depending on location (Westerling and Swetnam 2003; Schoennagel et al. 2005; Kitzberger et al. 2007). At latitudes north of ~45°N, historic fires commonly burned during droughts associated with El Niño phases (Westerling and Swetnam 2003; Trouet et al. 2006). In the Pacific Northwest of the USA and western Canada, El Niño phases are associated with shallow snow packs, early melt, 75  longer growing and fire seasons, and higher temperatures (Heyerdahl et al. 2002; Pohl et al. 2002; Hessl et al. 2003; Westerling and Swetnam 2003; Kitzberger et al. 2007; Heyerdahl et al. 2008). In my study, seven out of eight fires burned after 1863 during well-documented El Niño phases (Mote et al. 1999; Garcia-Herrera et al. 2006; Li et al. 2011; Yu and Kim 2013). Prior to 1863, no fires burned during El Niño phases; however, few studies report El Niño data at an annual resolution prior to 1870. It is possible that ENSO-fire relations changed through time. Johnson and Larsen (1991) suggest climate has been cooler and wetter since the end of the Little Ice Age. Short term droughts related to El Niño phases might only have become more important recently. To test this hypothesis more fire data and reliable pre-1870 ENSO records are needed.  I found fires were associated with the negative phase of the PDO, which contrasts with other studies in the western Cordillera (Hessl et al. 2004; Gedalof et al. 2005; Kitzberger et al. 2007; Da Silva 2009), including Schoennagel et al.’s (2005) analysis of fires around Jasper townsite. Half of the fires I documented, including two widespread fires in 1889 and 1905, burned during the long negative PDO phase from 1840 to 1922. Of the remaining nine fires that formed scars prior to 1840, five burned during positive PDO phases including widespread fires in 1772 and 1827. Schoennagel et al. (2005) used 72 fire-scar dates reported by Tande (1977, 1979) for the area around Jasper townsite. Those fire-scar dates are based on ring counts and subsequent crossdating of samples which show several errors (L. Daniels, personal communication July 2012). When I compared my fire-scars dates with Tande’s (1977, 1979) records, I found that eight dates, all of which fell between the mid-19th and early 20th centuries, matched: 1915, 1905, 1901, 1896, 1889, 1878, 1863 and 1846. Six fire-scar dates differed by ≤3 years: 1890, 1831, 1772, 1740, 1724, 1711 and 1677. Only one of these, 1890, was after the mid-76  19th century. All of the rest were between the late 17th and early 19th centuries. Two fire dates, 1827 and 1706, differed by five or six years whereas my oldest fire-scar date, 1646, differed from Tande’s (1977, 1979) oldest fire-scar date, 1665, by 19 years. It is likely some of these discrepancies could be due to crossdating issues.   Another difference is Schoennagel et al.’s (2005) study was based on D’Arrigo et al.’s (2001) tree-ring reconstruction of the PDO which spans from 1700 to 1979. Apart from the shorter time span of the reconstruction which did not capture two of my fire years (1646 and 1677), post-hoc analyses showed other differences between reconstructions. The correlation between D’Arrigo et al.’s (2001) and Gedalof and Smith’s (2001) PDO reconstruction for the 1700 to 1979 interval was relatively low (0.374). Moreover, the result from a superposed epoch analysis using D’Arrigo et al.’s (2001) reconstruction showed a non-significant trend between the positive phase of the PDO and fire occurrence consistent with Schoennagel et al.’s (2005) study.  Fauria and Johnson (2008) associate the occurrence of widespread fires on the west/east side of the Canadian Rockies with negative/positive PDO phases and place JNP at the boundary between different PDO phase influences. However, Fauria and Johnson (2006, 2008) use records  of fire extents spanning from 1959-1999 and 1918-2005, respectively, when a strong fire suppression effect has been identified in many regions of North America (White 1985; Fulé et al. 1997; Brown et al. 1999; Taylor 2000; Veblen et al. 2000; Taylor and Skinner 2003; Hessl et al. 2004; Schoennagel et al. 2004; Arienti et al. 2006), therefore it is not clear if their findings are applicable to understand historic climate-fire interactions. My findings suggested JNP is located 77  in a regional climate that differs from study areas further south in the Rocky Mountains and east in the boreal. “Dipoles” in teleconnections are well documented further south (Westerling and Swetnam 2003; Schoennagel et al. 2005; Trouet et al. 2006; Kitzberger et al. 2007; Heyerdahl et al. 2008; Pederson et al. 2011). To effectively discern effects of teleconnections on the historic fire regime I would need more fire-scar data.  3.4.2 Multi-decadal variation in fire frequency The multi-decadal variation in my fire scar record for the montane forests in JNP, were similar to long-term patterns in other fire reconstructions in western North America. I found: (1) a declining number of fire scars prior to 1772; (2) no fire scars between 1773 and 1826; (3) many fire scars between 1827 and 1915; and (4) no fire scars after 1915. Much of this variation is consistent with well-documented climate variation at the continental to hemispheric spatial scales and with land use changes (Meyn et al. 2007). Both likely explained the variation in fire occurrence in JNP.  Between 1646 and 1772, seven fires burned with one fire every 18 years in the study area, on average. Fires were recorded during this period even though only 39 sites had trees that established prior to 1773 and 9 sites included recorder trees. Fire was likely more frequent than indicated by the fire-scar record due to “disappearing evidence”, an inherent limitation of fire-scar studies (Swetnam et al. 1999). Successive fires, mechanical damage and wood decomposition effectively remove recorders of fire thus decreasing the chances of finding older fire-scar dates (Van Pelt and Swetnam 1990; Parsons et al. 2007; Swetnam et al. 2011).   78  From 1773 to 1826, no fire scars were recorded in my study area. The lack of fire during this period is consistent with the well-documented “fire gap” throughout western North America (Veblen et al. 2000; Heyerdahl et al. 2002; Brown 2006; Sibold and Veblen 2006; Trouet et al. 2006; Kitzberger et al. 2007) and in northern Patagonia in South America (Kitzberger et al. 2001; Veblen and Kitzberger 2002; Kitzberger and Veblen 2003). The potential cause of the fire gap has been attributed to broad-scale climatic variation given the common patterns in North and South America (Kitzberger et al. 2001, 2007). Specifically, the fire gap has been linked to the coldest phase of the Atlantic Multidecadal Oscillation (AMO) since the mid-1600s (Kitzberger et al. 2007); however, I did not find a statistical association between the AMO and fire occurrence in JNP. Alternately, widespread changes in land use throughout North and South America were concurrent with this period (Meyn et al. 2007). Written and oral records indicate smallpox epidemics in the 1780s and 90s affected First Nation communities in JNP and both east and west of the Rocky Mountains (Johnson and Larsen 1991; Wikeem and Ross 2002; Murphy et al. 2007; Payne 2007). In parallel, tuberculosis, influenza, measles and typhoid fever also led to First Nation peoples’ sickness and death in the 18th and 19th centuries across North America (Durie 2003; Waldram et al. 2006). Depopulation would result in a strong decrease in fire ignitions since archaeological and historic records show evidence of First Nation use of fire in the region (Anderson and Reeves 1975; Francis 1997; Hudecek-Cuffe 2000; Murphy 2007; Murphy et al. 2007).  From 1827 to 1915, fires were most frequent and included three widespread fires. High fire frequency in the late 19th and early 20th centuries is a common pattern in fire history studies throughout North America (Veblen et al. 2000; Taylor and Skinner 2003; Beaty and Taylor 79  2008) and South America (Veblen et al. 1999), which reflects climate conditions favourable to fire, increased use of fire by settlers and better conservation of fire-scar evidence. During this period, seven out of eight fires in JNP burned during El Niño phases. The weak relationship with the negative phase of the PDO particularly over the prolonged phase between 1840 and 1922 contrasted with other climate-fire studies conducted in the western Cordillera. Other climate-fire analyses found fires tended to be associated with positive PDO phases (Hessl et al. 2004; Schoennagel et al. 2005; Heyerdahl et al. 2008; Da Silva 2009). Of all these studies, only Hessl et al.’s (2004) used Gedalof and Smith’s (2001) PDO reconstruction; however, they did not use the identified multi-decadal phases. Rather Hessl et al. (2004) compared the PDO indices on an annual basis against the fire dates whereas I used the multi-decadal positive and negative phases identified by Gedalof and Smith (2001). Other climate-fire analyses in the western Cordillera used D’Arrigo et al.’s (2001) or MacDonald and Case’s (2005) PDO reconstructions. Since tree-ring based reconstructions of climate patterns have relatively low correlations especially prior to the 20th century differences between climate-fire interaction analyses are likely (Watson and Luckman 2005). The lack of a relationship with the AMO contrasted with Kitzberger et al.’s (2007) study which found positive AMO phases were related to higher-than-expected fire synchrony across western North America. This period coincided with the presence of increasing European explorers and peoples of mixed-ancestry in Jasper, as well as the establishment of several posts and homesteads within and near the study area, and the development of the Grand Trunk Pacific railway along the Athabasca River (Murphy 2007; Murphy et al. 2007; Payne 2007; Taylor 2007). Settlement has been linked to fire activity both in North and South America (Barrett and Arno 1982; Veblen et al. 1999; Veblen et al. 2000; Taylor and Skinner 2003; Schoennagel et al. 2004; Beaty and Taylor 2008; Jensen and McPherson 2008). 80   No fire scars were recorded after 1915 in the study area, although this is the period during which the sample depth and potential to record fires was greatest. Starting in 1919, I found live trees at 100% of the 172 sites. Since thin-barked Picea and Pinus contorta were the dominant species, chances were high that lower-severity fires would have scarred these trees. The lack of fire scars at all 172 sites for at least 82 consecutive years (1916-1997) is unprecedented in the 533-year fire record for the study area. Climatic variation alone could not explain the absence of fire scars since 1915. Tree-ring proxy indicators of drought and instrumental climate data indicated variable climatic conditions during the 20th century including relatively dry periods from 1916 to 1947 and 1983 to 2009 that were similar to the drought conditions in which historic fires burned. Climate during these periods appeared favourable for fire; however, the lack of scars implies either fire ignition or spread were limiting.   Evidence of lightning and human ignitions exists in the Canadian Rocky Mountain National Parks (Tyrrell 1916; Wierzchowski et al. 2002; Murphy 2007; Murphy et al. 2007; Parks Canada 2013). However, changes over time in rates of lightning strikes and ignitions are not evident (White 1985; Wierzchowski et al. 2002); however, there is strong evidence that human ignitions have changed substantively over time exists. Written, oral and archaeological records document historic and prehistoric First Nation use of fire within and near JNP over hundreds to thousands of years (Anderson and Reeves 1975; Francis 1997; Hudecek-Cuffe 2000; Murphy 2007; Murphy et al. 2007). Written and oral records convey how families living in and nearby the study area between 1895 and 1910 lit fires in the spring to create forage for local wildlife and facilitate hunting (Murphy et al. 2007). However, after 1913, prohibition of fire use 81  and the displacement of local people excluded fire from the landscape (Murphy 2007; Murphy et al. 2007).   Fire suppression has directly affected fire regimes in the national parks in western North America during the 20th century (Barrett and Arno 1982; Arno 1985; Gruell 1985; Veblen et al. 2000; Taylor and Skinner 2003; Schoennagel et al. 2004; Jensen and McPherson 2008). Following the implementation of a fire protection and suppression policy in 1913 within JNP (Murphy et al. 2007), park managers were mandated to suppress fires before they spread in size or to an intensity that was difficult to control. Over time, enhanced fire-fighting training, access and equipment have increased the capacity to detect and rapidly suppress fires (Tande 1979; Murphy 1985, Fulé et al. 1997; Brown et al. 1999; Taylor 2000; Veblen et al. 2000; Arienti et al. 2006). For example fire records from Parks Canada (2013) include 101 lightning-ignitions since 1940, eight of which resulted in fires >40 ha in size. Only six wildfires were ignited by lightning in my study area and all were between 2004 and 2009; however, all were suppressed before they exceeded one ha in size.   3.5 Conclusion  The montane forests of Jasper National Park (JNP) provided evidence both climate and humans have influenced the historic fire regime. In particular, the recent absence of fire was associated with a period of active fire suppression in JNP. Eighteen fires from 1646 to 1915 burned during droughts, which had a weak association with the El Niño phase, especially since 1863, and the negative phase of the Pacific Decadal Oscillation. To better understand climate drivers I would need additional data from JNP. Although the climate-fire relations at the inter-82  annual level were ambiguous, multi-decadal scale trends were consistent between JNP and many fire-scar based studies in western North and South America. After accounting for the depleting fire-scar record, fire frequency varied through time consistent with continental to inter-hemispheric climate drivers and changes in land use, including settlement by Europeans, loss of First Nation peoples and their cultural use of fire, and fire suppression policies and practice. JNP provided a long, well-documented human use of fire in montane forests. The increase in fire frequency in the 1800s and early into the 20th century corresponded with settlement; however, fires at that time also consistently burned during El Niño phases. Since 1915, I found a lack of fire scars despite potential recorder trees at all sites and multi-year/decade periods when climate was conducive to fire. Park records substantiated the realisation of fire suppression and its consequent effect on the historic fire regime. 83  Table 3.1 Summary of the fire records for 115 sites west of the Athabasca River. 84  Table 3.1 Continued  85  Table 3.2 Summary of the fire records for 57 sites east of the Athabasca River.  86    Figure 3.1 Fire history sites (n = 172) in the Athabasca River valley in montane and subalpine forests of Jasper National Park. Fire-scar dates are in red. Year of establishment of the oldest tree per site are in black. Squares are homesteads established from 1895 and 1910. Triangles are suppressed lightning-ignited fires from 2004 to 2009. In the inset map, JH2 = Jasper House II (1826-1884), LH = Larocque House (1824-1825), HH = Henry House (1811-1830s) and PP = Pyramid and Patricia lakes.  87   Figure 3.2 Fire history records from 1465 to 2012 at 172 sites. Horizontal lines represent the site-level composite tree-ring records (top to bottom: sites 1 to 115 west of the Athabasca River left column; sites 116 to 172 east of the Athabasca River right column). The length of each line represents the period of record, starting from the pith of the oldest tree to 1997-2000 or 2012 when trees were sampled. Fire evidence includes crossdated, annually-resolved fire scars. For sites lacking fire scars, dashed lines indicate the length of the record determined by the age of the oldest living tree.  88   Figure 3.3 Composite fire records from 1600 to 2012 for a) the 115 sites west of the Athabasca River, b) the 57 sites east of the Athabasca River and c) all 172 sites in the study area. In each composite fire record, the graph shows the number of sites with fire scars (black line) and the number of sites recording a fire (grey bars) over time.   1600 1700Year1800 1900 20000450102002001020N o .   o f    s i t e s   w i t h   f i r e   s c a r s02501020N o .   o f   s i t e s   r e c o r d i n g   f i r ec) All study sites (n = 172)a) West of Athabasca River (n = 115)b) East of Athabasca River (n = 57) 89   Figure 3.4 Climate-growth relations for Pseudotsuga menziesii from 1902 to 2009. Bars are the correlation function coefficients between the Pseudotsuga menziesii residual chronology and monthly precipitation, maximum temperature, and heat-moisture indices and the (top to bottom). Dots are significant correlation function coefficients (α = 0.05).        Correlationcoefficients-0.4-0.20.00.20.4Maximum temperature-0.4-0.20.00.20.4PrecipitationM o n t h a n d s e a s o n r e l a t i v e t o r i n g f o r m a t i o nSummer(prior)Summer(current)Winter(prior)A M J J A S O N D J F M A M J J A S-0.4-0.20.00.20.4Heat-moisture index 90   Figure 3.5 Fire occurrence (black dots) from 1646 to 1985 relative to inter-annual to multi-decadal variation in climate. The residual ring-width chronology represents drought (top), followed by ENSO, PDO and AMO indices reconstructed from tree rings (Cook et al. 2009; Gedalof and Smith 2001; Gray et al. 2004, respectively). Within panels (top to bottom), dark grey (white) areas represent dry (wet) periods (Watson and Luckman 2004), El Niño (non-El Niño) events (Garcia-Herrera et al. 2008; Yu and Kim 2013), positive (negative) phases of the PDO (Gedalof and Smith 2001) and AMO (Gray et al. 2004) time series. For the AMO, light grey areas represent neutral phases (Gray et al. 2004). Residual Index-3-2-10123ENSO Index-2-1012PDO Index-2-1012Year1650 1700 1750 1800 1850 1900 1950AMO Index-3-2-10123 91    Figure 3.6 Departure (%) from the mean of fire years (year 0) relative to the four years preceding and two years following fire for the a) residual chronology, b) ENSO, c) PDO and d) AMO climate patterns from 1642 to 1917. Two dots are significant correlation function coefficients (α = 0.01) derived from 1,000 Monte Carlo simulations.   a) Residual chronology-4 -3 -2 -1 0 1 2-101-101Departure (%)frommean-101-4 -3 -2 -1 0 1 2-101b) ENSOc) PDOd) AMOYears relative to fire (0) 92    Figure 3.7 Tests of association between fire (black) and non-fire (white) years and climatic variation. Years from 1645 to 1915 are stratified by a) multi-year periods of dry and wet climate, b) ENSO (El Niño and non-El Niño), c) positive (+) and negative () PDO, and d) positive (+), neutral (n) and negative () AMO phases, and e-g) two-way interactions between ENSO, PDO and AMO. Chi-squared goodness of fit and p-values indicate significant tests ( = 0.05).  00.20.40.60.8El Niño non-El Niño00.20.40.60.8+PDOEl Niño-PDO +PDOnon-El Niño-PDO00.20.40.60.8b)e)a)DryMulti-year climateENSO phasesENSO x PDO phases+AMOEl NiñonAMO nAMO nAMO nAMO-AMO +AMOnon-El Niño-AMO +AMO+PDO-AMO +AMO-PDO-AMOProportion of yearsProportion of yearsProportion of yearsWetχ  = 4.156p = 0.0412χ  = 2.296p = 0.1302+PDO -PDOc)PDO phasesχ  = 1.355p = 0.2442+AMO nAMO -AMOd)AMO phasesχ  = 0.274p = 0.8722f)ENSO x AMO phasesg)PDO x AMO phases 93   Figure 3.8 Annual ring-width indices by fire years and periods from 1646 to 2009. In each box plot, the black horizontal line represents the median and box boundaries are the 25th and 75th percentiles; bars are the 10th and 90th percentiles; and different letters denote significant differences among mean values (α = 0.05).  Annual ring-width indices012Dryperiod1916-1947Wetperiod1948-1982Unclassifiedperiod1983-2009Dryperiods1646-1915Wetperiods1646-1915Fireyears1646-1915aababbab 94    Figure 3.9 Annual precipitation (top), maximum temperature (middle) and heat-moisture indices (bottom) by period from 1916 to 2009. In each box plot, the black horizontal line represents the median and box boundaries are the 25th and 75th percentiles; bars are the 10th and 90th percentiles; and different letters denote significant differences among mean values (α = 0.05). Dryperiod1916-1947Wetperiod1948-1982Unclassifiedperiod1983-2009Annual precipitation (mm)4006008001000120014001600Annual maximum temperature (°C)56789101112Annual heat-moisture indices01020304050abcabaabab 95  Chapter 4: Conclusions 4.1 Summary and Contribution to Research My thesis contributes to the understanding of the influence of mixed-severity fire regimes and their drivers in the montane forests of Jasper National Park (JNP). The traditional paradigm was that high-severity fire regimes were prevalent in the Canadian Rocky Mountains (Johnson et al. 1990; Masters 1990); however, my findings at a network of sites estimated the fire regime was of mixed-severity with a greater component of high-severity rather than low-severity fires (Chapter 2). This difference in fire regimes is subtle yet the significance for JNP’s forest management is important. Planning for fire hazard mitigation, the protection of species at risk and the restoration of the mixed-severity fire regime as a fundamental ecological process within JNP can benefit from my crossdated, annually resolved fire records. My exploration of climate-fire interactions indicated that fires were most likely to burn during drought years (Chapter 3). Associations with regional-scale climate teleconnections were weak; however, additional crossdated fire records within Jasper and over a broader area in the Southern Canadian Cordillera would increase statistical power and improve understanding of climatic drivers. Such knowledge is needed to support risk and hazard assessments and to plan for future forest and wildfire management given climate change.  4.1.1 Importance of dendrochronological analyses Identifying fire-scar years, even-aged and post-fire cohorts, and veteran trees surviving fires were criteria to classify and differentiate the severity of historic fires through time at individual sites (Chapter 2; Sherriff and Veblen 2006; Heyerdahl et al. 2012). At sites with mixed-severity fire histories, age structures were significantly more discontinuous than at high- 96  severity sites. Mixed-severity sites also had greater diversity in age, size and species than high-severity fire history sites, although differences were not statistically significant. The patterns of uneven and discontinuous age and size structures and tree species diversity at mixed-severity sites that I observed were consistent with other research on mixed-severity fire regimes (Amoroso et al. 2011; Halofsky et al. 2011; Perry et al. 2011; Marcoux et al. 2013). However, wide variation among sites classified as mixed- versus high-severity fire history class made the classes difficult to differentiate without detailed information on tree ages and fire-scar dates.  My comparative analyses of canopy and subcanopy strata between fire-history classes showed composition and size-structure indices were poor indicators of historical fire severity. As a result, the type of information derived from aerial photographs or remote sensing technologies and recorded in standard vegetation resource inventories, and the standard measurements of forest composition and tree size included in field-based timber cruises, will not effectively distinguish sites of different fire histories. To best understand the historic fire regime, detailed dendrochronological analyses are essential to reconstruct disturbance-related mechanisms and processes of change and to differentiate sites with mixed- versus high-severity fire histories.  4.2 Management Implications 4.2.1 Fire regimes and management In many forests of western North America, tree composition is shifting towards shade-tolerant but fire-intolerant species due to fire exclusion (Taylor and Solem 2001; Fulé et al. 2003; Beaty and Taylor 2008; Bekker and Taylor 2010; Perry et al. 2011). In JNP ongoing shifts in species composition were subtle. Forest composition was strongly influenced by past high- 97  severity fires that resulted in even-aged cohorts in the stem-exclusion or under re-initiation stages of stand development. Subcanopy trees were slow-growing poor competitors with limited potential to recruit to the canopy; however, the sapling stratum of most sites was dominated by shade-tolerant, fire-intolerant Picea. Over time, the recruitment of suppressed Picea saplings as canopy gaps form due to tree senescence and/or within stand disturbances would lead to a decrease in species diversity within and among stands. Subcanopy Picea also creates ladder fuels and increases the risk of crown fire. Given the widespread increase in closed-canopy forests in JNP (Rhemtulla et al. 2002), many of which are at similar stages of stand development with increasing ladder fuels due to fire exclusion during the 20th century (Chapter 2), there is risk that the landscape-scale fire regime could shift from a mixed-severity fire regime to exclusively a high-severity, stand-replacing fire regime.  The cumulative effects of homogenization of stand structures, compositional shifts towards Picea and increasing ladder fuels, increase the chance of large crown fires in the montane forests. In combination with climate change, the cumulative effects could jeopardize resilience of montane forests in JNP. In the advent of a wildfire occurring under extreme weather conditions (Johnson and Wowchuck 1993; Bessie and Johnson 1995; Nash and Johnson 1996; Westerling et al. 2006), the greatest impacts would be most likely at sites with mixed-severity fire histories (Schoennagel et al. 2004; Perry et al. 2011). Thus, my results support management actions that increase forest compositional and structural diversity such as thinning, burning and modified response to wildfires. Such active management will restore structures and processes associated with mixed-severity fires and mitigate risk of high-severity fires in locations that would pose a threat to park residents, visitors and infrastructure (Westhaver et al. 2007).   98   4.2.2 Importance of mixed-severity fires for at risk Rangifer tarandus and Ursus arctos populations Wildlife managers in the Canadian Rocky Mountain parks and adjacent areas are concerned about the fragmentation and quality of habitat for at risk woodland caribou (Rangifer tarandus caribou Gmelin) and grizzly bear (Ursus arctos horribilis Linnaeus) populations (O’Neill 2011; Environment Canada 2012). My fire records provided evidence mixed-severity fires historically characterized portions of the landscape (Chapter 2). Mixed-severity fire regimes produce a range of effects on vegetation, including enhancing landscape heterogeneity (Lertzman and Fall 1998; Perry et al. 2011) and providing habitat diversity (Halofsky et al. 2011). Since woodland caribou and grizzly bear require a sequence of seasonal habitat conditions for their wellbeing (Terry et al. 2001; Munro et al. 2006; Nielson et al. 2006; Environment Canada 2012; Stenhouse and Graham 2012), restoring onto portions of the Park’s landscape and surrounding forests of the Rocky Mountain Foothills a mixed-severity fire regime or a silvicultural treatment which emulates a range of fire effects similar to a mixed-severity fire regime could provide and/or enhance habitat quality for at risk populations.  4.3 Future Research 4.3.1 Importance of human versus lightning ignitions Variation in fire frequency over decades in JNP suggested both humans and climate influenced the historical fire regime. However, differentiating human versus lightning sources of ignition for historic fires is very difficult. To better understand the human component I propose to develop fire records for a paired analysis of fire history at sites of similar biophysical  99  characteristics where one group of sites would be adjacent to archaeological sites whereas another group of sites would be removed from archaeological sites. Results could be integrated in a geographic information system to identify whether spatial patterns exist between historic fire occurrence and archaeological sites. To develop a more complete fire scar record, oral history and archaeology could provide further evidence of First Nation peoples’ use of fire in the Park.  4.3.2 Monitoring regeneration and fuel  Monitoring the stands at my network of sites would test the hypothesis that the successional trajectory of increasing Picea at stand to landscape scales. It would also identify sites in which forest composition and structure present a fuel hazard. The observed regeneration in the network of sites was predominantly Picea. In the absence of fire, future regeneration is most likely to continue to be Picea as it is shade tolerant and does not need exposed mineral soil to regenerate (Burns and Honkala 1990; Klinka et al. 2002). Quantifying and monitoring fuels at my sites would anticipate local fire effects should a fire burn there.  4.3.3 Climate-fire relations  To better understand climate-fire interactions in JNP would require annually resolved fire-scar records with sufficient fire dates. Increasing the amount of data would also improve understanding of historic human ignited fires in the Park. Theresa Dinh, M.Sc. candidate, at the University of Guelph, Ontario, crossdated 170 fire-scarred samples from Tande’s (1977, 1979) study. In addition to increasing the number of crossdated fire-scar samples in JNP, a second approach would be to compare fire records among the Canadian Rocky Mountain parks and in the Canadian Cordillera. Expanding the current study to include annually-resolved fire-scar  100  records from Kootenay National Park (Kubian 2013), the montane forests of the Southern Rocky Mountain Trench in British Columbia (BC) (Cochrane 2007; Daniels et al. 2011) and the Joseph and Gold Creek watersheds near Cranbrook, BC (Da Silva 2009; Marcoux 2013; Marcoux et al. 2013) would allow a regional-scale assessment of the associations between spatio-temporal climate patterns and fire. Improved knowledge of variation of climate-fire interactions over the Southern Canadian Cordillera would help to anticipate the conditions conducive to extreme fire events, especially given projected climate change in the region. It would also support the practice of ecosystem-based management guided by range of fire-disturbance variation.     101  References Agee, J.K. (1981). Fire effects on Pacific Northwest forests: Flora, fuels, and fauna. In: Northwest Forest Council proceedings, Northwest Forest Fire Council, Portland, OR, USA. pp. 54–66. Agee, J.K. (1993). Fire Ecology of Pacific Northwest Forests. Island Press, Washington DC, DC, USA. 493 p. Agee, J. K. (1997). The severe weather wildfire: Too hot to handle? Northwest Science, 71: 253–256. Agee, J.K. (1998). The landscape ecology of western forest fire regimes. Northwest Science, 72: 24–34. Allan, R.J. (2000). ENSO and climatic variability in the past 150 years. In: Diaz, H.F. and Markgraf, V. (eds). El Niño and the Southern Oscillation: Multiscale variability and global and regional impacts. Cambridge University Press, Cambridge, UK. pp. 3–55. Allen, C.D., Macalady, A.K., Chenchouni, H., Bachelet, D., McDowell, N., Vennetier, M., Kitzberger, T., Rigling, A., Breshears, D.D., Hogg, E.H., Gonzalez, P., Fensham, R., Zhang, Z., Castro, J., Demidova, N., Lim, J., Allard, G., Running, S.W., Semerci, A. and Cobb, N. (2009). A global overview or drought and heat-induced tree mortality reveals emerging climate change risks for forests. Forest Ecology and Management, 259: 660–684. Amoroso, M.M., Daniels, L.D., Bataneih, M. and Andison, D.W. (2011). Evidence of mixed-severity fires in the foothills of the Rocky Mountains of west-central Alberta, Canada. Forest Ecology and Management, 262: 2240–2249, doi:10.1016/j.foreco.2011.08.016. Anderson, R. and Reeves, B.O.K. (1975). Jasper National Park Archaeological Inventory. National Historic Parks and Sites Branch Manuscript Report Number 158, Parks Canada, Ottawa. 185 p.  102  Andison, D.W. (2012). The influence of wildfire boundary delineation on our understanding of burning patterns in the Alberta foothills. Canadian Journal of Forest Research, 42(7): 1253–1263, doi:10.1139/X2012-074. Antos, J.A. and Parish, R. (2002). Dynamics of an old-growth, fire-initiated, subalpine forest in southern interior British Columbia: Tree size, age, and spatial structure. Canadian Journal of Forest Research, 32(11): 1935–1946, doi:10.1139/X02-116. Arienti, M.C., Cumming, S.G. and Boutin, S. (2006). Empirical models of forest fire initial attack success probabilities: The effects of fuels, anthropogenic linear features, fire weather, and management. Canadian Journal of Forest Research, 36(12): 3155–3166, doi:10.1139/X06-188. Arno, S.F. (1985). Ecological effects and management implications of Indian fires. In: Lotan, J.E., Kilgore, B.M, Fischer, W.C. and Mutch, R.W. (eds.). Proceedings: Symposium and workshop on wilderness fire, Missoula, MT, USA. General technical report INT-182. Intermountain Forest and Range Experiment Station, U.S. Forest Service, Ogden, UT, USA.  pp. 81–86. Arno, S.F. and Fiedler, C.E. (2005). Mimicking nature’s fire: Restoring fire-prone forests in the West. Island Press, Washington DC, DC, USA. 242 p. Bahre, C.J. (1991). A Legacy of change: Historic human impact on vegetation in the Arizona borderlands. University of Arizona Press, Tucson, AZ, USA. 231 p. Baisan, C.H. and Swetam, T.W. (1990). Fire history on a desert mountain range: Rincon Mountain Wilderness, Arizona, USA. Canadian Journal of Forest Research, 20: 1559–1569. Baker, F.S. (1949). A revised tolerance table. Journal of Forestry, 47: 179–181. Balling, R.C., Meyer, G.A. and Wells, S.G. (1992a) Relation of surface climate and burned area in Yellowstone National Park. Agricultural and Forest Meteorology, 60: 285–293.  103  Balling, R.C., Meyer, G.A. and Wells, S.G. (1992b). Climate change in Yellowstone National Park: is the drought-related risk of wildfires increasing? Climatic Change, 22: 35–45. Barrett, S.W. (1988). Fire suppression's effects on forest succession within a central Idaho wilderness. Western Journal of Applied Forestry, 3: 76–80. Barrett, S.W. and Arno, S. (1982). Indian fires as an ecological influence in the northern Rockies. Journal of Forestry, 80: 647–651. Beamish, R.J., Neville, C.M. and Cass, A.J. (1997). Production of Fraser River sockeye salmon (Oncorhynchus nerka) in relation to decadal scale changes in the climate and the ocean. Canadian Journal of Fisheries and Aquatic Sciences, 56: 516–526. Beaty, M.R. and Taylor, A.H. (2008). Fire history and the structure and dynamics of a mixed conifer forest landscape in the northern Sierra Nevada, Lake Tahoe Basin, California, USA. Forest Ecology and Management, 225: 707–719, doi:10.1016/j.foreco.2007.09.044. Bekker, M.F. and Taylor, A.H. (2010). Fire disturbance, forest structure, and stand dynamics in montane forests of the southern Cascades, Thousand Lakes Wilderness, California, USA. Écoscience, 17(1): 59–72, doi:10.2980/17-1-3247. Bergeron, Y. and Archambault, S. (1993). Decreasing frequency of forest fires in the southern boreal zone of Québec and its relation to global warming since the end of the ‘Little Ice Age’. The Holocene, 3(3): 255–259, doi:10.1177/095968369300300307. Bergeron, Y., Gauthier, S., Kafka, V., Lefort, P. and Lesieur, D. (2000). Natural fire frequency for the eastern Canadian boreal forest: Consequences for sustainable forestry. Canadian Journal of Forest Research, 31(3): 384–391, doi:10.1139/cjfr-31-3-384. Bessie, W.C. and Johnson, E.A. (1995). The relative importance of fuels and weather on fire behaviour in subalpine forests. Ecology, 76: 747–762, doi:10.2307/1939341.  104  Biondi, F. and Waikul, K. (2004). Dendroclim2002: A C++ program for statistical calibration of climate signals in tree-ring chronologies. Computers & Geosciences, 30: 303–311, doi:10.1016/j.cageo.2003.11.004. Biondi, F., Gershunov, A. and Cayan, D.R. (2001). North Pacific decadal climate variability since 1661. Journal of Climate, 14: 5–10. Bitz, C.M. and Battisti, D.S. (1999). Interannual to decadal variability in climate and the glacier mass balance in Washington, Western Canada, and Alaska. Journal of Climate, 12: 3181–3196. Bridgland, M.P. (1924). Photographic surveying, Department of the Interior, Ottawa, ON, Canada. Topographical Survey of Canada, 56 Brown, P.M. (2006). Climate effects on fire regimes and tree recruitment in Black Hills ponderosa pine forests. Ecology, 87(10): 2500–2510. Brown, P.M. and Swetnam, T.W. (1994). A cross-dated fire history from coast redwood near Redwood National Park, California. Canadian Journal of Forest Research, 24: 21–31. Brown, P.M., Kaufmann, M.R. and Shepperd, W.D. (1999). Long-term, landscape patterns of past fire events in a montane ponderosa pine forest of central Colorado. Landscape Ecology, 14(6): 513–532. Buechling, A. and Baker, W.L. (2004). A fire history from tree rings in a high-elevation forest of Rocky Mountain National Park. Canadian Journal of Forest Research, 34: 1259–1273. Burns, R.M. and Honkala, B.H. (1990). Silvics of North America: Volume 1, Conifers. Agriculture Handbook 654. U.S. Department of Agriculture, Forest Service, Washington, DC, USA. 675 p.  Chavardès, R.D., Daniels, L.D., Waeber, P.O, Innes, J.L. and Nitschke, C.R. (2012). Unstable climate-growth relations for white spruce in southwest Yukon, Canada. Climatic Change, 16: 593–611, doi:10.1007/s10584-01-0503-8.    105  Cochrane, J.D. (2007). Characteristics of historical forest fires in complex mixed-conifer forests of southeastern British Columbia. MSc thesis, University of British Columbia, Vancouver, BC, Canada. Cochrane, J.D. and Daniels, L.D. (2008). Striking a balance: Safe sampling of partial stem cross-sections in British Columbia. BC Journal of Ecosystems and Management, 9(1): 38–46. Cohen, J., Foster, J., Barlow, M., Saito, K. and Jones J. (2010). Winter 2009–2010: A case study of an extreme Arctic Oscillation event. Geophysical Research Letters, 37, L17707: 1–6, doi:10.1029/2010GL044256. Cohen, S. and Miller, D.C. (1978). The big burn: The Northwest’s forest fire of 1910. Pictorial Histories Publishing Company, Missoula, MT, USA. 88 p. Cole, J.E. (2001). A slow dance for El Niño. Science, 291: 1496–1497. Cole, J.E., Overpeck, J.T. and Cook, E.R. (2002). Multiyear La Niña events and persistent drought in the contiguous United States. Geophysical Research Letters, 29(13): 1–4 doi:10.1029/2001GL013561. Cook, E.R. (1985). A time series analysis approach to tree-ring standardization. PhD thesis, University of Arizona, Tucson, AZ, USA. Cook, E.R. (1992). Using tree rings to study past El Niño/Southern Oscillation influences on climate. In: Diaz, H.F. and Markgraf, V. (eds). El Niño: Historical and paleoclimatic aspects of the Southern Oscillation. Cambridge University Press, Cambridge, UK. pp. 203–241. Cook, E.R. and Holmes, R.L. (1986). User manual for program ARSTAN. In: Holmes, R.L., Adams, R.K. and Fritts, H.C. (eds). Tree-ring chronologies of Western North America, California, Eastern Oregon and Northern Great Basin. University of Arizona Press, Tucson, AZ, USA. pp. 50–65.  106  Cook, E.R, D’Arrigo R.D. and Anchukaitis, K.J. (2009). Tree ring 500 year ENSO index reconstructions. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2009-105. NOAA/NGDC Paleoclimatology program, Boulder, CO, USA. Retrieved from: www.ncdc.noaa.gov/paleo/recons.html [Verified 10 August, 2013]. Covington, W.W. and Moore, M.M. (1994a). Southwestern ponderosa pine forest structure and resource conditions: Changes since Euro-American settlement. Journal of Forestry, 92(1): 39–47. Covington, W.W. and Moore, M.M. (1994b). Postsettlement changes in natural fire regimes: Ecological restoration of old-growth ponderosa pine forests. Journal of Sustainable Forestry, 2: 153–181, doi:10.1300/J091v02n01_07. Cumming, S.G. (2005). Effective fire suppression in boreal forests. Canadian Journal of Forest Research, 35: 772–786, doi:10.1139/X04-174. Cumming, G.S. and Collier, J. (2005). Change and identity in complex systems. Ecology and Society, 10: 1–13. Curtis, J.T. and McIntosh, R.P. (1951). An upland forest continuum in the prairie-forest border region of Wisconsin. Ecology, 32: 476–496. Cyr, D., Gauthier, S. and Bergeron, Y. (2007). Scale-dependent determinants of heterogeneity in fire frequency in a coniferous boreal forest of eastern Canada. Landscape Ecology, 22(9): 1325–1339, doi:10.1007/s10980-007-9109-3. D'Arrigo, R., Villalba, R. and Wiles, G. (2001). Tree-ring estimates of Pacific decadal climate variability. Climate Dynamics, 18: 219–224. D'Arrigo, R.D., Cook, E.R., Mann, M.E. and Jacoby, G.C. (2003).Tree-ring reconstructions of temperature and sea-level pressure variability associated with the warm-season Arctic Oscillation since AD 1650. Geophysical Research Letters, 30(11): 1549, doi:10.1029/2003GL017250.  107  D'Arrigo R., Cook, E.R., Wilson, R.J., Allan, R. and Mann, M.E. (2005). On the variability of ENSO over the past six centuries. Geophysical Research Letters, 32, L03711: 1–4, doi:10.1029/2004GL022055. Daniels, L.D. and Watson, E. (2003). Climate-fire-vegetation interactions in the Cariboo Forests: A dendrochronological analysis. Forest Innovation and Investment Forest Research Program Final Report. 57 p. Daniels, L.D., Cochrane, J. and Gray, R.W. (2007). Mixed-severity fire regimes: Regional analysis of the impacts of climate on fire frequency in the Rocky Mountain Forest District. Report to Tembec Inc., BC Division, Canadian Forest Products Ltd., Radium Hot Springs, and the Forest Investment Account of British Columbia, BC, Canada. 36 p. Daniels, L.D., Maertens, T.B., Stan, A.B., McCloskey, S.P.J., Cochrane, J.D. and Gray, R.W. (2011). Direct and indirect impacts of climate change on forests: Three case studies from British Columbia. Canadian Journal of Plant Pathology, 33(2): 108–116, doi:10.1080/07060661.2011.563906. Da Silva, E. (2009). Historic controls of wildfire in the Joseph-Gold Creek Watershed, British Columbia: Implications of climate change and fire suppression. MSc thesis, University of Guelph, Guelph, ON, Canada. Dale, V.H., Joyce, L.A., McNulty, S., Neilson, R.P., Ayres, M.P., Flannigan, M.D., Hanson, P.J., Irland, L.C., Lugo, A.E., Peterson, C.J., Simberloff, D., Swanson, F.J., Stocks, B.J. and Wotton, M.B. (2001). Climate change and forest disturbances. BioScience, 51(9): 723–734. Dey, D.C. and Guyette, R.P. (2000). Anthropogenic fire history in red oak forests in South-Central Ontario. The Forestry Chronicle, 76(2): 339–347. Diaz, H.F. and Kiladis, G.N. (1992). Atmospheric teleconnections associated with the extreme phases of the Southern Oscillation. In: Diaz, H.F. and Markgraf, V. (eds). El Niño: Historical and paleoclimatic aspects of the Southern Oscillation. Cambridge University Press, Cambridge, UK. pp. 7–28.  108  Dieterich, J.H. and Swetnam, T.W. (1984). Dendrochronology of a fire-scarred ponderosa pine. Forest Science, 30(1): 238–247. Dillon, W.R. and Goldstein, M. (1984). Multivariate analysis: Methods and application. John Wiley and Sons, New York, NY, USA. pp. 163–367. Dobbs, R.C. (1976). White spruce seed dispersal in Central British Columbia. The Forestry Chronicle, 52: 225–228. Duncan, R. (1989). An evaluation of errors in tree age estimates based on increment cores in kahikatea (Dacrycarpus dacrydioides). New Zealand Natural Sciences, 16: 31–37. Ehle, D. and Baker, W.L. (2003). Disturbance and stand dynamics in ponderosa pine forests in Rocky Mountain National Park, USA. Ecological Monographs, 73(4): 543–566. Enfield, D.B., Mestas-Nuñez, A.M. and Trimble, P.J. (2001). The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the continental U.S. Geophysical Research Letters, 28(10): 2077–2080. Environment Canada (2012). Recovery strategy for the woodland caribou (Rangifer tarandus caribou), boreal population, in Canada. Species at Risk Act, Recovery Strategy Series. Environment Canada, OT, Canada. 138 p. Environment Canada (2014). Canadian Climate Normals 1981–2010: Jasper, Alberta. National Climate Data and Information Archive, Ottawa, Ontario, Canada. Retrieved February 25, 2014, from: http://climate.weather.gc.ca/climate_normals/ [ESRI] Environmental Systems Research Institute Limited (2011). ArcGIS version 10. Environmental Systems Research Institute Limited, Redlands, CA, USA. Falk, D.A., Miller, C., McKenzie, D. and Black, A.E. (2007). Cross-scale analysis of fire regimes. Ecosystems, 10: 809–823, doi:10.1007/s10021-007-9070-7.  109  Fauria, M.M. and Johnson, E.A. (2006). Large-scale climatic patterns control large lightning fire occurrence in Canada and Alaska forest regions. Journal of Geophysical Research, 111, G04008: 1–17, doi:10.10289/2006JG000181. Fauria, M.M. and Johnson, E.A. (2008). Climate and wildfires in the North American boreal forest. Philosophical Transactions of the Royal Society Biological Sciences, 363: 2315–2327, doi: 10.1098/rstb.2007.2202. Fauria, M.M., Michaletz, S.T. and Johnson, E.A. (2011). Predicting climate change effects on wildfires requires linking processes across scales. Wiley Interdisciplinary Reviews: Climate Change, 2(1): 99–112, doi:10.1002/wcc.92. Fedorov, A.V. and Philander, S.G. (2000). Is El Niño changing? Science, 288(5473): 1997–2002. Ferguson, C.W. and Parker, M.L. (1965). IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series CANA026. NOAA/NGDC Paleoclimatology program, Boulder, CO, USA. Retrieved from: www.ncdc.noaa.gov/paleo/recons.html [Verified 15 March, 2012]. Filmon, G. (2004). Firestorm 2003 provincial review. Government of British Columbia, BC, Canada. 100 p. Retrieved July 20, 2013, from: http://www.2003firestorm.gov.bc.ca/firestormreport/FirestormReport.pdf. Flannigan, M.D., Stocks, B.J. and Weber, M.G. (2003). Fire regimes and climatic change in Canadian forests. In: Veblen, T., Baker, W. and Swetnam, T. (eds.). Fire and climatic change in temperate ecosystems of the western americas. Springer-Verlag, New York, NY, USA. pp. 97–119. Flannigan, M.D., Bergeron, Y., Engelmark, O. and Wotton, B.M. (1998). Future wildfire in circumboreal forests in relation to global warming. Journal of Vegetation Science, 9: 469–476, doi: 10.2307/3237261.  110  Flannigan, M.D., Stocks, B.J., Turetsky, M.R. and Wotton, B.M. (2008). Impacts of climate change on fire activity and fire management in the circumboreal forest. Global Change Biology, 15: 549–560, doi: 10.1111/j.1365-2486.2008.01660.x. Folke, C., Carpenter, S., Walker, B., Scheffer, M., Elmqvist, T., Gunderson, L. and Holling, C.S. (2004). Regime shifts, resilience, and biodiversity in ecosystem management. Annual Review of Ecology, Evolution, and Systemics, 35: 557–581, doi:10.1146/annurev.ecolsys.35.021103.10511. Francis, P.D. (1997). Threatened archaeological sites in the mountain parks. Cultural Resource Management, 20(4): 39–42. Franklin, J.F., Spies, T.A., Pelt, R.V., Carey, A.B., Thornburgh, D.A., Berg, D.R., Lindenmayer, D.B., Harmon, M.E., Keeton, W.S., Shaw, D.C., Bible, K. and Chen, J. (2002). Disturbances and structural development of natural forest ecosystems with silvicultural implications, using Douglas-fir forests as an example. Forest Ecology and Management, 155(1-3): 399–423. Frelich, L.E. and Reich, P.B. (1999). Neighborhood effects, disturbance severity, and community stability in forests. Ecosystems, 2: 151–166. Fritts, H.C. (1976). Tree rings and climate. Academic Press Incorporated, London, UK. 567 p. Fulé, P.Z., Covington, W.W. and Moore, M.M. (1997). Determining reference conditions for ecosystem management of southwestern ponderosa pine forests. Ecological Applications, 7(3): 895–908. Fulé, P.Z., Crouse, J.E., Heinlein, T.A., Moore, M.M., Covington, W.W. and Verkamp, G.  (2003). Mixed-severity fire regime in a high-elevation forest: Grand Canyon, Arizona. Landscape Ecology, 18: 465–486. Gadd, B. (1986). Handbook of the Canadian Rockies. Corax Press, Jasper, AB, Canada. 831 p.  111  Gedalof, Z. and Smith, D.J. (2001). Interdecadal climate variability and regime-scale shifts in Pacific North America. Geophysical Research Letters, 28(8): 1515–1518. Gedalof, Z., Peterson, D.L. and Mantua, N.J. (2005). Atmospheric, climatic and ecological controls on extreme wildfire years in the northwestern United States. Ecological Applications, 15(1): 154–174. Gershunov, A. and Barnett, T.P. (1998). Interdecadal modulation of ENSO teleconnections. Bulletin of the American Meteorological Society, 79(12): 2715–2725. Gershunov, A., Barnett, T.P. and Cayan, D.R. (1999). North Pacific interdecadal oscillation seen as factor in ENSO-related North American climate anomalies. EOS, Transactions, American Geophysical Union, 80: 25–30, doi:10.1029/99EO00019. Government of Canada (2013). Get prepared. Wildfires. Retrieved March 10, 2014, from: http://www.getprepared.gc.ca/cnt/hzd/wldfrs-eng.aspx. Gray, S.T., Graumlich, L.J., Betancourt, J.L. and Pederson, G.T. (2004a). A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A.D., Geophysical Research Letters, 31, L12205: 1–4, doi:10.1029/2004GL019932. Gray, S.T., Graumlich, L.J., Betancourt, J.L. and Pederson, G.T. (2004b). Atlantic Multidecadal Oscillation (AMO) index reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-062 NOAA/NGDC Paleoclimatology program, Boulder, CO, USA. Retrieved from: www.ncdc.noaa.gov/paleo/recons.html [Verified 10 August, 2013]. Greene, D.F. and Johnson, E.A. (2000). Tree recruitment from burn edges. Canadian Journal of Forest Research, 30: 1264–1274. Greene, G.A. (2011). Historical fire regime of the Darkwoods: Quantifying the past to plan for the future. MSc thesis, University of British Columbia, Vancouver, BC, Canada.  112  Grissino-Mayer, H.D. (2001a). Evaluating crossdating accuracy: A manual and tutorial for the computer program COFECHA. Tree-Ring Research, 57(2): 205–221. Grissino-Mayer, H.D. (2001b). FHX2–Software for analyzing temporal and spatial patterns in fire regimes from tree rings. Tree-Ring Research, 57(1): 115–124. Grissino-Mayer, H.D. and Swetnam , T.W. (2000). Century-scale climate forcing of fire regimes in the American Southwest. Holocene, 10(2): 213–220, doi:10.1191/095968300668451235. Gruell, G.E. (1985). Indian fires in the interior West. In: Lotan, J.E., Kilgore, B.M, Fischer, W.C. and Mutch, R.W. (eds.). Proceedings: symposium and workshop on wilderness fire, Missoula, MT, USA. General technical report INT-182, Intermountain Forest and Range Experiment Station, U.S. Forest Service, Ogden, UT, USA. pp. 68–74. Gutsell, S.L. and Johnson, E.A. (2002). Accurately ageing trees and examining their height-growth rates: Implications for interpreting forest Dynamics. Journal of Ecology, 90: 153–166. Halofsky, J.E., Donato, D.C., Hibbs, D.E., Campbell, J.L., Cannon, M.D., Fontaine, J.B., Thompson, J.R., Anthony, R.G., Bormann, B.T., Kayes, L.J., Law, B.E., Peterson, D.L. and Spies, T.A. (2011). Mixed-severity fire regimes: Lessons and hypotheses from the Klamath-Siskiyou Ecoregion. Ecosphere, 2(4): 1–19, doi:10.1890/ES10-00184.1. Hartmann, B. and Wendler, G. (2005). The significance of the 1976 Pacific climate shift in the climatology of Alaska. Journal of Climate, 18: 4824–4839. Heinselman, M.L. (1973). Fire in the virgin forests of the Boundary Waters Canoe Area, Minnesota. Quaternary Research, 3: 329–385. Heinselman, M.L. (1981). Fire and succession in the conifer forests of North America. In: West, D.C., Shugart, H.H. and Botkin, D.B. (eds.). Forest succession: Concepts and application. pp. 374–406.  113  Hessl, A.E., McKenzie, D. and Schellhaas, R. (2004). Drought and Pacific Decadal Oscillation linked to fire occurrence in the inland Pacific Northwest. Ecological Applications, 14(2): 425–442, doi:10.1890/03-5019. Hessl, A., Miller, J., Kernan, J., Keenum, D. and McKenzie, D. (2007). Mapping paleo-fire boundaries from binary point data: Comparing interpolation methods. The Professional Geographer, 59(1): 87–104. Hessburg, P.F., Salter, R.B. and James, K.M. (2005). Dry forests and wildland fires of the inland Northwest USA: Contrasting the landscape ecology of the pre-settlement and modern eras. Forest Ecology and Management, 211(1-2): 117–139, doi:10.1015/j.foreco.2005.02.016. Hessburg, P.F., Salter, R.B. and James, K.M. (2007). Re-examining fire severity relations in pre-management era mixed conifer forests: inferences from landscape patterns of forest structure. Landscape Ecology, 22: 5–24, doi:10.1007/s10980-007-9098-2. Heyerdahl, E.K., Brubaker, L.B. and Agee, J.K. (2001). Spatial controls of historical fire regimes: A multiscale example from the interior west, USA. Ecology, 82(3): 660–678. Heyerdahl, E.K., Brubaker, L.B. and Agee, J.K. (2002). Annual and decadal climate forcing of historical fire regimes in the interior Pacific Northwest, USA. Holocene, 12(5): 597–604, doi:10.1191/0959683602hl570rp. Heyerdahl, E.K., Miller, R.F. and Parson, R.A. (2006). History of fire and Douglas-fir establishment in a savanna and sagebrush-grassland mosaic, southwestern Montana, USA. Forest Ecology and Management, 230: 107–118, doi:10.1016/j.foreco.2006.04.024. Heyerdahl, E.K., Lertzman, K. and Karpuk, S. (2007). Local-scale controls of a low-severity fire regime (1750–1950), southern British Columbia, Canada. Écoscience, 14(1): 40–47. Heyerdahl, E.K., Lertzman, K. and Wong, C.M. (2012). Mixed-severity fire regimes in dry forests of southern interior British Columbia, Canada. Canadian Journal of Forest Research, 42: 88–98, doi:10.1139/X11-160.  114  Heyerdahl, E.K., McKenzie, D., Daniels, L.D., Hessl, A.E., Littell, J.S. and Mantua. N.J. (2008). Climate drivers of regionally synchronous fires in the inland Northwest (1651–1900). International Journal of Wildland Fire, 17: 40–49, doi:10.1071/WF07024. Hidalgo, H.G. (2004). Climate precursors of multidecadal drought variability in the western United States. Water Resources Research, 40, W12504: 1–10, doi: 10.1029/2004WR003350. Holland, W.D. and Coen, G.M. (1982). Ecological (biophysical) land classification of Banff and Jasper National Parks, Volume II, Soil and vegetation resources. Alberta Institute of Pedology Publication, Edmonton, AB, Canada. 603 p. Hudecek-Cuffe, C. (2000). Final report Department of Anthropology University of Alberta archaeological field school Jasper National Park, July 13–August 19, 1998. Permit No. WRA 98-03. 241 p. [IPCC] Intergovernmental Panel on Climate Change (2007a). Climate change 2007: Impacts, adaptation and vulnerability. Cambridge University Press, Cambridge, UK. 842 p. [IPCC] Intergovernmental Panel on Climate Change (2007b). Climate change 2007: The physical science basis. Cambridge University Press, Cambridge, UK. 940 p. [IPCC] Intergovernmental Panel on Climate Change (2013). Climate change 2013: The physical science basis. Cambridge University Press, Cambridge, UK. 1552 p. Jensen, S.E. and McPherson, G.R. (2008). Living with fire: Fire ecology and policy for the twenty-first century. University of California Press, Berkeley, CA, USA. 180 p. Li, J. Xie, S., Cook, E.R., Huang, G., D’Arrigo, R., Liu, F., Ma, J. and Zheng, X. (2011). Interdecadal modulation of El Niño amplitude during the past millennium. Nature Climate Change, 1: 114–118, doi:10.1038/nclimate1086. Johnson, E.A. (1992). Fire and vegetation dynamics: Studies from the North American boreal forest. Cambridge University Press, New York, NY, USA. 129 p.  115  Johnson, E.A. and Van Wagner, C.E. (1985) The theory and use of two fire history models. Canadian Journal of Forest Research, 15: 214–220. Johnson, E.A. and Larsen, C.P.S. (1991) Climatically induced change in fire frequency in the Southern Canadian Rockies. Ecological Society of America, 72(1): 194–201. Johnson, E.A. and Wowchuk, D.R. (1993). Wildfires in the Southern Canadian Rocky Mountains and their relationship to mid-tropospheric anomalies. Canadian Journal of Forest Research, 23: 1213–1222. Johnson, E.A. and Gutsell, S.L. (1994). Fire frequency models, methods and interpretations. Advances in Ecological Research, 25: 239–287. Johnson, E.A., Fryer, G.I. and Heathcott, M.J. (1990). The influence of man and climate on the fire frequency in the interior Wet Belt Forest, British-Columbia. Journal of Ecology, 78: 403–412. Johnson, E.A., Miyanishi, K. and Weir, J.M.H. (1998). Wildfires in the Western Canadian boreal forest: Landscape patterns and ecosystem management. Journal of Vegetation Science, 9: 603–610. Johnson, E.A., Miyanishi, K. and O’Brien, N. (1999). Long-term reconstruction of the fire season in the mixedwood boreal forest of Western Canada. Canadian Journal of Botany, 77: 1185–1188. Johnson, E.A., Miyanishi, K. and Bridge, S.R.J. (2001). Wildfire regime in the boreal forest and the idea of suppression and fuel buildup. Conservation Biology, 15: 1554–1557. Jonsson, B., Holm, S. and Kallur, H. (1992). A forest inventory method based on density-adapted circular plot size. Scandinavian Journal of Forest Research, 7(1-4): 405–421. Jordan, G.J., Fortin, M.J. and Lertzman, K. (2005). Assessing spatial uncertainty associated with forest fire boundary delineation. Landscape Ecology, 20(6): 719–731, doi:10.1007/s10980-005-0071-7.  116  Jordan, G.J., Fortin, M.J. and Lertzman, K. (2008). Spatial pattern and persistence of historical fire boundaries in southern interior British Columbia. Environmental Ecological Statistics, 15: 523–535, doi:10.1007/s1061-007-0063-7. Kay, C.E. (1995). Aboriginal overkill and native burning: Implications for modern ecosystem management. Western Journal of Applied Forestry, 10: 121–126. Kay, C.E., and White, C.A. (1995). Long-term ecosystem states and processes in the central Canadian Rockies: A new perspective on ecological integrity and ecosystem management. In: Linn, R.E. (ed.). Contributed Papers of the 8th Conference on Research and Resource Management in Parks and on Public Lands, 17–21 April 1995, Portland, OR, USA. The George Wright Society, Hancock, MI, USA. pp. 119–132. Kernan, J.T. and Hessl, A.E. (2010). Spatially heterogeneous estimates of fire frequency in ponderosa pine forests of Washington, USA. Fire Ecology, 6(3): 117–135, doi:10.4496/fireecology.0603117. Kerr, R.A. (2000). A North Atlantic climate pacemaker for the centuries. Science, 288: 1984– 1986. Kimmins, J.P. (2004). Forest Ecology: A foundation for sustainable management. Prentice-Hall, Upper Saddle River, NJ, USA. 611 p. Kipfmueller, K.F. and Baker, W.L. (1998). A comparison of three techniques to date stand-replacing fires in lodgepole pine forests. Forest Ecology and Management, 104: 171–177. Kipfmueller, K.F. and Baker, W.L. (2000). A fire history of a subalpine forest in south-eastern Wyoming, USA. Journal of Biogeography, 27: 71–85. Kitzberger, T. and Veblen, T.T. (2003). Influences of climate on fire in Northern Patagonia, Argentina. In: Veblen, T.T., Baker, W.L., Montenegro, G. and Swetnam, T.W. (eds.). Fire and climatic change in temperate ecosystems of the western Americas. Springer-Verlag, New York, NY, USA. pp. 296–321, doi:10.1007/0-387-21710-X_10.  117  Kitzberger, T., Swetnam, T.W. and Veblen, T.T. (2001). Inter-hemispheric synchrony of forest fires and the El Niño-Southern Oscillation. Global Ecology and Biogeography, 10: 315–326. Kitzberger, T., Brown, P.M., Heyerdahl, E.K., Swetnam, T.W. and Veblen, T.T. (2007). Contingent Pacific-Atlantic Ocean influence on multi-century wildfire synchrony over western North America. Proceedings of the National Academy of Sciences of the USA, 104(2): 543–548, doi:10.1073/pnas.0606078104. Klinka, K., Worrall, J., Skoda, L. and Varga, P. (2000). The distribution and synopsis of the ecological and silvical characteristics of tree species of British Columbia’s forests. Canadian Cartographics Limited, Coquitlam, BC, Canada. 180 p. Knight, J.R., Folland, C.K. and Scaife, A.A. (2006). Climate impacts of the Atlantic Multidecadal Oscillation. Geophysical Research Letters, 33, L17706: 1–4, doi: 10.1029/2006GL026242. Kottek, M., Grieser, J., Beck, C., Rudolf, B. and Rubel, F. (2006). World map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift, 15: 259–263.  Kubian, R. (2013). Characterizing the mixed-severity fire regime of the Kootenay Valley, Kootenay National Park. MSc thesis, University of Victoria, Victoria, BC, Canada. Larsson, L. (2011a). CooRecorder program of the CDendro package version 7.4. Cybis Elektronik & Data AB. Retrieved September 15, 2011, from: http://www.cybis.se. Larsson, L. (2011b). CDendro program of the CDendro package version 7.4. Cybis Elektronik & Data AB. Retrieved September 15, 2011, from: http://www.cybis.se. Lentile, L.B., Smith, F.W. and Shepperd, W.D. (2006). Influence of topography and forest structure on patterns of mixed severity fire in ponderosa pine forests of the South Dakota Black Hills, USA. International Journal of Wildland Fire, 15(4): 557–566, doi:10.1071/WF05096.  118  Lertzman, K.P. and Fall, J. (1998). From forest stands to landscapes: Spatial scales and the roles of disturbances. In: Peterson, D.L. and Parker, V.T. (eds.). Ecological scale: Theory and applications. Columbia University Press, New York, NY, USA. pp. 339–367. Lertzman, K., Fall, J. and Dorner, B. (1998). Three kinds of heterogeneity in fire regimes: At the crossroads of fire history and landscape ecology. Northwest Science, 72: 4–23. Lessard, V.C., Drummer, T.D. and Reed, D.D. (2002). Precision of density estimates from fixed-radius plots compared to n-tree distance sampling. Forest Science, 48(1): 1–6. Lewis, H.T. (1985). Why Indians burned: Specific versus general reasons. In: Lotan, J.E., Kilgore, B.M., Fischer, W.C., and Mutch, R.W. (eds.). Proceedings, symposium and workshop on wilderness fire. Intermountain Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, Missoula, MT, USA. pp. 75–86. Linsley, B.K., Wellington, G.M. and Shrag, D.P. (2000). Decadal sea surface temperature variability in the subtropical South Pacific from 1726 to 1997 A.D. Science, 290: 1145–1148, doi:10.1126/science.290.5494.1145. Littell, J.S., Oneil, E.E., McKenzie, D., Hicke, J.A., Lutz, J.A., Norheim, R.A. and Elsner, M.M. (2010). Forest ecosystems, disturbance, and climatic change in Washington State, USA. Climatic Change, 102: 129–158, doi:10.1007/s10584-010-9858-x. Longley, R.W. (1970). Climatic classification for Alberta forestry. In: Powell, J.M. and Nolasco, C.F. (eds). Proceedings of the third microclimate symposium. Canadian Department of Fisheries and Forestry, Canadian Forest Service, Forest Research Laboratory, Calgary, AB, Canada, pp. 147–153. MacDonald, G.M. and Case, R.A. (2005). Variations in the Pacific Decadal Oscillation over the past millennium. Geophysical Research Letters, 32, L08703: 1–4, doi:10.1029/2005GL022478. MacLaren, I.S. (2007). Introduction. In: MacLaren, I.S. (ed.). Culturing wilderness in Jasper National Park. The University of Alberta Press, Edmonton, AB, Canada. pp. XV–XLIII.  119  Magne, M. (1997). How much archaeological inventory in large national parks is enough? Cultural Resource Management, 20(4): 33–35. Mahalanobis, P. (1930). On tests and measures of group divergence. Journal and Proceedings of the Asiatic Society of Bengal, 26: 541–588. Malone, M.P., Roeder, R.B. and Lang, W.L. (1991). Montana: A history of two centuries. University of Washington Press, Seattle, WA, USA. 466 p. Mantua, N.J., Hare, S.R., Zhang, Y., Wallace, J.M. and Francis, R.C. (1997). A Pacific interdecadal climate oscillation with impact on salmon production. Bulletin of the American Meteorological Society, 78: 1–11. Mantua, N.J. and Hare, S.R. (2002). The Pacific decadal oscillation. Journal of Oceanography, 58: 35–44. Marcoux, H.M., Gergel, S.G. and Daniels, L.D. (2013). Mixed-severity fire regimes: How well are they represented by existing fire-regime classification systems? Canadian Journal of Forest Research, 43(7): 658−668, doi:10.1139/cjfr-2012-0449. Marcoux, H.M., Daniels, L.D., Gergel, S.G., Da Silva, E., Gedalof, Z.M. and Hessburg, P.F. Reconsidering the evidence for mixed- versus high-severity fire regimes in mixed-conifer forests. Submitted. Margolis, E.Q. and Balmat, J. (2009). Fire history and fire–climate relationships along a fire regime gradient in the Santa Fe Municipal Watershed, NM, USA. Forest Ecology and Management, 258(11): 2416–2430, doi:10.1016/j.foreco.2009.08.019. Martell, D.L. (2001). Forest fire management. In: Johnson E.A. and Miyanishi, K. (eds.). Forest fires: Behavioural and ecological effects. Academic Press, London, UK. pp. 527–583. Masters, A.M. (1990). Changes in forest fire frequency in Kootenay National Park, Canadian Rockies. Canadian Journal of Botany, 68: 1763–1767.  120  McCabe, G.J., and Dettinger, M.D. (1999). Decadal variations in the strength of ENSO teleconnections with precipitation in the Western United States. International Journal of Climatology, 19: 1399–1410. McCabe, G.J., Palecki, M.A. and Betancourt, J.L. (2004). Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States. Proceedings of the National Academy of Sciences of the United States of America, 101(12): 4136–4141, doi:10.1073/pnas.0306738101. McCabe, G.J., Betancourt, J.L., Gray, S.T., Palecki, M.A. and Hidalgo, H.G. (2008). Associations of multi-decadal sea-surface temperature variability with US drought. Quaternary International, 188: 31–40. McKenzie, D., Gedalof, Z., Peterson, D.L. and Mote, P. (2004). Climatic change, wildfire, and conservation. Conservation Biology, 18: 890–902. Meyer, D.A. and Roe, J. (2007). Archaeology along Canada's Rocky Mountain eastern slopes: Excavations at the Upper Lovett campsite, Alberta. Expedition, 49(2): 28–35. Meyn, A., White, P.S., Buhk, C. and Jentsch, A. (2007). Environmental drivers of large, infrequent wildfires: The emerging conceptual model. Progress in Physical Geography, 31(3): 287–312, doi:10.1177/0309133307079365. Millar, C.I. and Woolfenden, W.B. (1999). The role of climate change in interpreting historical variability. Ecological Applications, 9(4): 1207–1216. Millar, C.I., Stephenson, N.L. and Stephens, S.L. (2007). Climate change and forests of the future: Managing in the face of uncertainty. Ecological Applications, 17(8): 2145–2151. Miller, A.M. (2010). Living with boreal forest fires: Anishinaabe perspectives on disturbance and collaborative forestry planning, Pikangikum First Nation, Northwestern Ontario. PhD thesis, University of Manitoba, Winnipeg, MB, Canada.  121  Min, S., Zhang, X. and Zwiers, F. (2008). Human-induced Arctic moistening. Science, 320(5875): 518–520, doi:10.1126/science.1153468. Minobe, S. (1997). A 50–70 year climatic oscillation over the North Pacific and North America. Geophysical Research Letters, 24: 683–686, doi: 10.1029/97GL00504. Minobe, S. (2000). Spatio-temporal structure of the pentadecadal variability over the North Pacific. Progress in Oceanography, 47: 381–408, doi:10.1016/S0079-6611(00)00042-2. Morgan, J.L, Gergel, S.E. and Coops, N.C. (2010). Aerial photography: A rapidly evolving tool for ecological management. BioScience, 60(1): 47–59, doi:10.1525/bio.2012.60.1.9. Morgan, P., Hardy, C.C., Swetnam, T.W., Rollins, M.G. and Long, D.G. (2001). Mapping fire regimes across time and space: Understanding coarse and fine-scale fire patterns. International Journal of Wildland Fire, 10: 329–342, doi:10.1071/WF01032. Mote, P., Canning, D., Fluharty, D., Francis, R., Franklin, J., Hamlet, A., Hershman, M., Holmberg, M., Ideker, K.G., Keeton, W., Lettenmaier, D., Leung, R., Mantua, N., Miles, E., Noble, B., Parandvash, H., Peterson, D., Snover, A. and Willard, S. (1999). Impacts of climate variability and change: Pacific Northwest. JIASO Climate Impacts Group, Office of Global Programs, National Oceanic and Atmospheric Administration, University of Washington, Seattle, WA, USA. 116 p. Munro, R.H.M., Nielson, S.E., Price, M.H., Stenhouse, G.B. and Boyce, M.S. (2006). Seasonal and diel patterns or grizzly bear diet and activity in West-Central Alberta. Journal of Mammalogy, 87(6): 1112–1121, doi:10.1644/05-MAMM-A-410R3.1. Murphy, P.J. (1985). History of forest and prairie fire control policy in Alberta. Alberta Energy and Natural Resources, Edmonton, AB, Canada. 407 p. Murphy, P.J. (2007). “Following the base of the foothills”: Tracing the boundaries of Jasper Park and its adjacent Rock Mountains Forest Reserve. In: MacLaren I.S. (ed.). Culturing wilderness in Jasper National Park. The University of Alberta Press, Edmonton, AB, Canada. pp.  71–121.  122  Murphy, P.J., Udell, R., Stevenson, R.E. and Peterson, T.W. (2007). A hard road to travel: Land, forests and people in the Upper Athabasca region. Foothills Model Forest, Hinton, AB, Canada. 306 p. Nash, C.H. and Johnson, E.A. (1996). Synoptic climatology of lightning-caused forest fires in subalpine and boreal forests. Canadian Journal of Forest Research, 26: 1859–1874. Nesbitt, J.H. (2010). Quantifying forest fire variability using tree rings Nelson, British Columbia 1700–present. MSc thesis, University of British Columbia, Vancouver, BC, Canada. Neu, D. and Graham, C. (2006). The birth of a nation: Accounting and Canada’s First Nations, 1860–1900. Accounting, Organizations and Society, 31(1): 47–76, doi:10.1016/j.aos.2004.10.002. Nielson, S.E., Stenhouse, G.B and Boyce, M.S. (2006). A habitat-based framework for grizzly bear conservation in Alberta. Biological Conservation, 130(2): 217–229, doi:10.1016/j.biocon.2005.12.016. Oliver, C.D. and Larson, B.C. (1996). Forest stand dynamics. John Wiley and Sons, New York, NY, USA. 467 p. O’Neill, N.A. (2011). Transboundary regional planning collaboration for climate change adaptation: A case study of Jasper National Park, Mount Robson Provincial Park, and Willmore Wilderness Park. MSc thesis, University of Waterloo, Waterloo, ON, Canada. Parker, A.J. (1982). The topographic relative moisture index: An approach to soil-moisture assessment in mountain terrain. Physical Geography, 3(2): 160–168. Parks Canada (2013). Fire ignition and suppression geospatial database 1929–2012: Jasper National Park, AB, Canada. Received October 21, 2013, from Parks Canada. Parsons, R.A., Heyerdahl, E.K., Keane, R.E, Dorner, B. and Fall, J. (2007). Assessing accuracy of point fire intervals across landscapes with simulation modelling. Canadian Journal of Forest Research, 37(9): 1605–1614, doi:10.1139/X07-013.  123  Payette, S. (1992). Fire as a controlling process in the North American boreal forest. In: Shugart, H.H., Leemans, R. and Bonan, G.B. (eds.). A systems analysis of the global boreal forest. Cambridge University Press, New York, NY, USA. pp. 144–169. Payne, M. (2007).The fur trade on the Upper Athabasca River, 1810–1910. In: MacLaren, I.S. (ed.). Culturing wilderness in Jasper National Park. The University of Alberta Press, Edmonton, AB, Canada. pp. 1–39. Pederson, G.T., Gray, S.T., Woodhouse, C.A., Betancourt, J.L, Fagre, D.B., Littell, J.S., Watson, E., Luckman, B.H. and Graumlich, L.J. (2011). The unusual nature of recent snowpack declines in the North American Cordillera. Science, 333(6040): 332–335, doi:10.1126/science.1201570. Peet, R.K. (2000). Forests and meadows of the Rocky Mountains. In: Barbour, M.G. and Billings, W.D. (eds.). North American terrestrial vegetation. Cambridge University Press, New York, NY, USA. pp. 76–121. Perry, D.A., Hessburg, P.F., Skinner, C.N., Spies, T.A., Stephens, S.L., Taylor, A.H., Franklin, J.F., McComb, B. and Riegel, G. (2011). The ecology of mixed severity fire regimes in Washington, Oregon, and Northern California. Forest Ecology and Management, 262(5): 703–717, doi:10.1016/j.foreco.2011.05.004. Pierce, J.L., Meyer, G.A. and Jull, T.A.J. (2004). Fire-induced erosion and millennial-scale climate change in northern ponderosa pine forests. Nature, 432: 87–90, doi:10.1038/nature03058. Podur, J.J. and Martell, D.L. (2009). The influence of weather and fuel type on the fuel composition of the area burned by forest fires in Ontario, 1996–2006. Ecological Applications, 19(5): 1246–1252. Pohl, K.A., Hadley, K.S. and Arabas, K.B. (2002). A 45-year drought reconstruction for central Oregon. Physical Geography, 23(4): 302–320.  124  Powell, S., Daniels, L. and Jones, T. (2009). Temporal dynamics of large woody debris in small streams of the Alberta foothills, Canada. Canadian Journal of Forest Research, 39: 1159–1170. Price, C. and Rind, D. (1994). The impact of a 2 X CO2 climate on lightning-caused fires. Journal of Climate, 7: 1484–1494. Rajora, O.P. and Dancik, B.P. (2000). Population genetic variation, structure, and evolution in Engelmann spruce, white spruce, and their natural hybrid complex in Alberta. Canadian Journal of Botany, 78: 768–780. Redmond, K.T. and Koch, R.W. (1991). Surface climate and streamflow variability in the western United States and their relationship to large–scale circulation indices. Water Resources Research, 27: 2381–2399. Reeves, B.O.K. (1974). Prehistoric archaeological research on the eastern slopes of the Canadian Rocky Mountains 1967–1971. Canadian Archaeological Association, 6: 1–31. Rhemtulla, J.M., Hall, R.J., Higgs, E.S. and Macdonald, S.E. (2002). Eighty years of change: Vegetation in the montane ecoregion of Jasper National Park, Alberta, Canada. Canadian Journal of Forest Research, 32: 2010–2021, doi:10.1139/X02-112. Rogeau, M.P. (1999). Detailed disturbance history mapping of the montane, Jasper National Park 1997–1998. Unpublished report to Foothills Research Institute. 44 p. Romme, W.H. and Despain, D.G. (1989). Historical perspective on the Yellowstone fires of 1988. BioScience, 39: 695–699. Romme, W.H. and Knight, D.H. (1981). Fire frequency and subalpine forest succession along a topographic gradient in Wyoming. Ecology, 62(2): 319–326. Rothermel, R.C. (1983). How to predict the spread and intensity of forest and range fires. General Technical Report INT-143. U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station, Ogden, UT, USA. 161 p.  125  Sanborn, P., Lamontagne, L. and Hendershot, W. (2011). Podzolic soils of Canada: Genesis, distribution, and classification. Canadian Journal of Soil Science, 91: 843–880, doi:10.4141/CJSS10024. Sarachik, E.S. and Cane, M.A. (2010). The El Niño–Southern Oscillation phenomenon. Cambridge University Press, Cambridge, UK. 369 p. SAS Institute Incorporated (2011). SAS 9.3 Documentation. SAS Institute Incorporated, Cary, NC, USA. Retrieved October 10, 2011, from: http://support.sas.com/documentation/93/index.html. Schoennagel, T., Veblen, T.T. and Romme, W.H. (2004). The interaction of fire, fuels, and climate across Rocky Mountain forests. Bioscience, 54: 661–676, doi:10.1641/0006-3568(2004)054[0661:TIOFFA]2.0.CO;2. Schoennagel, T., Veblen, T.T., Kulakowski, D. and Holz, A. (2007). Multidecadal climate variability and climate interactions affect subalpine fire occurrence, western Colorado (USA). Ecology, 88: 2891–2902. Schoennagel, T., Veblen, T.T., Romme W.H., Sibold, J.S. and Cook, E.R. (2005). ENSO and PDO variability affect drought-induced fire occurrence in Rocky Mountain subalpine forests. Ecological Applications, 15(6): 2000–2014. Scholl, A.E. and Taylor, A.H. (2010). Fire regimes, forest change, and self-organization in an old-growth mixed-conifer forest, Yosemite National Park, USA. Ecological Applications, 20(2): 362–380, doi:10.1890/08-2324.1. Seager, R.M., Tzanova, A. and Nakamura, J. (2007). Model projections of an imminent transition to a more arid climate in Southwestern North America. Science, 316: 1181–1184. Shannon, C.E. and Weaver, W. (1949). The mathematical theory of communication. University of Illinois Press, Urbana, IL, USA. 125 p.  126  Sherriff, R.L. and Veblen, T.T. (2006). Ecological effects of changes in fire regimes in Pinus ponderosa ecosystems in the Colorado Front Range. Journal of Vegetation Science, 17: 705–718. Sibold, J.S. and Veblen, T.T. (2006). Relationships of subalpine forest fires in the Colorado Front Range with interannual and multidecadal-scale climatic variation. Journal of Biogeography, 33: 833–842, doi:10.1111/j.1365-2699.2006.01456.x. Smith, C.A.S., Meikle, J.C. and Roots, C.F. (2004). Ecoregions of the Yukon Territory – Biophysical properties of Yukon landscapes. Agriculture and Agri-Food Canada, Summerland, BC, Canada. 313 p. Soverel, N.O. (2010). Validating burn severity classification using Landsat imagery across western Canadian National Parks. MSc thesis, University of British Columbia, Vancouver, BC, Canada. Stahle, D.W., D’Arrigo, R.D., Krusic, P.J., Cleaveland, M.K., Cook, E.R., Allan, R.J., Cole, J.E., Dunbar, R.B., Therrell, M.D., Gay, D.A., Moore, M.D., Stokes, M.A, Burns, B.T., Villanueva-Diaz, J. and Thompson, L.G. (1998). Experimental dendroclimatic reconstruction of the Southern Oscillation. Bulletin of the American Meteorological Society, 79(10): 2137–2152. Starker, T.J. (1934). Fire resistance in the forest. Journal of Forestry, 32: 462–467. Stenhouse, G. and Graham, K. (2012). Grizzly bear program 2011 annual report. Foothills Research Institute, Hinton, AB, Canada. 309 p. Stringer, P.W. and LaRoi, G.H. (1970). The Douglas-fir forests of Banff and Jasper National Parks, Canada. Canadian Journal of Botany, 48: 1703–1726. Stocks, B.J., Mason, J.A., Todd, J.B., Bosch, E.M., Wotton, B.M., Amiro, B.D., Flannigan, M.D., Hirsch, K.G., Logan, K.A., Martell, D.L. and Skinner, W.R. (2002). Large forest fires in Canada, 1959–1997. Journal of Geophysical Research: Atmospheres, 107 (D1): FFR 5-1–FFR5-12, doi:10.1029/2001JD000484.  127  Stokes, M.A. and Smiley, T.L. (1996). An introduction to tree-ring dating. University of Chicago Press, Chicago, IL, USA. 73 p. Sutton, R.T. and Hodson D.L.R. (2003). Influence of the ocean on North Atlantic climate variability 1871– 1999. Journal of Climate, 16: 3296– 3313. Sutton, R.T. and Hodson, D.L. (2005). Atlantic Ocean forcing of North American and European summer climate. Science, 309(5731): 115–118, doi:10.1126/science.1109496. Swetnam, T.W. (1993). Fire history and climate change in giant sequoia groves. Science, 262(5135): 885–889. Swetnam, T.W. and Betancourt, J.L. (1990). Fire-southern oscillation relations in the Southwestern United States. Science, 249: 1017–20. Swetnam, T.W. and Baisan, C.H. (1996). Historical fire regime patterns in the Southwestern United States since AD 1700. In: Allen, C.D. (ed.). Fire effects in Southwestern forests: Proceedings of the second La Mesa fire symposium, Los Alamos, NM, USA, March 29–31, 1994. Forest Service General Technical Report, RM-GTR-286, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO, USA. pp. 11–32. Swetnam, T.W. and Betancourt, J.L. (1998). Mesoscale disturbance and ecological response to decadal climatic variability in the American southwest. Journal of Climate, 11: 3128–3147. Swetnam, T.W. and Anderson, S.R. (2008). Fire climatology in the western United States: Introduction to special issue. International Journal of Wildland Fire, 17: 1–7, doi:10.1071/WF08016. Swetnam, T., Allen, C. and Betancourt, J. (1999). Applied historical ecology: Using the past to manage for the future. Ecological applications, 9(4): 1189-1206. Swetnam, T., Falk, D.A., Hessl, A.E. and Farris, C. (2011). Reconstructing landscape pattern of historical fires and fire regimes. In: McKenzie, D., Miller C. and Falk, D.A. (eds.). The landscape ecology of fire. Springer, New York, NY, USA. pp. 165–192.  128  Systat Software Incorporated (2013). Sigmaplot 12.5. Systat Software Incorporated, San Jose, CA, USA. Tande, G.F. (1977). Forest fire history around Jasper townsite, Jasper National Park, Alberta. MSc thesis, University of Alberta, Edmonton, AB, Canada. Tande, G.F. (1979). Fire history and vegetation pattern of coniferous forests in Jasper National Park, Alberta. Canadian Journal of Botany, 57: 1912–1931. Taylor, A.H. (2000). Fire regimes and forest changes in mid and upper montane forests of the southern Cascades, Lassen Volcanic National Park, California, USA. Journal of Biogeography, 27(1): 87–104. Taylor, A.H. and Skinner, C.N. (1998). Fire history and landscape dynamics in a late successional reserve, Klamath Mountains, California, USA. Forest Ecology and Management, 111: 285–301. Taylor, A.H. and Solem, M.N. (2001). Fire regimes and stand dynamics in an upper montane forest landscape in the southern Cascades, Caribou Wilderness, California. Journal of the Torrey Botanical Society, 128(4): 350–361. Taylor, A.H. and Skinner, C.N. (2003). Spatial patterns and controls on historical fire regimes and forest structure in the Klamath Mountains. Ecological Applications, 13(3): 704–719. Taylor, A.H. and Beaty, R.M. (2005). Climatic influences on fire regimes in the northern Sierra Nevada Mountains, Lake Tahoe Basin, Nevada, USA. Journal of Biogeography, 32(3): 425–438, doi:10.1111/j.1365-2699.2004.01208.x. Taylor, A.H., Trouet, V. and Skinner, C.N. (2008). Climatic influences on fire regimes in montane forests of the southern Cascades, California, USA. International Journal of Wildland Fire, 17: 60–71, doi:10.1071/WF07033.  129  Taylor, S.W., Pike, R.G. and Alexander, M.E. (1996). Field guide to the Canadian forest fire behaviour prediction (FBP) system. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC, Canada. 86 p. Taylor, C.J. (2007). The changing habitat of Jasper tourism. In: MacLaren, I.S. (ed.). Culturing wilderness in Jasper National Park. The University of Alberta Press, Edmonton, AB, Canada. pp. 199–231. Terry, E.L., McLellan, B.N. and Watts, G.S. (2001). Winter habitat ecology of mountain caribou in relation to forest management. Journal of Applied Ecology, 37: 589–602. Tyrrell, J.B. (ed.). (1916). David Thompson’s narrative. The Champlain Society, Toronto, ON, Canada. 582 p. Trenberth, K.E. and Hoar, T.J. (1997). El Niño and climate change. Geophysical Research Letters, 24(23): 3057–3060. Trouet, V., Taylor, A.H., Carleton, A.M. and Skinner, C.N. (2009). Interannual variations in fire weather, fire extent, and synoptic-scale circulation patterns in northern California and Oregon. Theoretical and Applied Climatology, 95: 349–360, doi: 10.1007/s00704-008-0012-x. Trouet, V., Taylor, A.H., Wahl, E.R., Skinner, C.N. and Stephens, S.L. (2010). Fire-climate interactions in the American West since 1400 CE. Geophysical Research Letters, 37, L04702: 1–5, doi: 10.1029/2009GL041695. Turner, M.G. (2010). Disturbance and landscape dynamics in a changing world. Ecology, 91(10): 2833–2849. Turner, M.G. and Romme, W.H. (1994). Landscape dynamics in crown fire ecosystems, Landscape Ecology, 9(1): 59–77. Turner, M.G., Romme, W.H. and Tinker, D.B. (2003). Surprises and lessons from the 1988 Yellowstone fires. Frontiers in Ecology and the Environment, 1(7): 351–358.  130  Turner, M.G., Hargrove, W.W., Gardner, R.H. and Romme, W.H. (1994). Effects of fire on landscape heterogeneity in Yellowstone National Park, Wyoming. Journal of Vegetation Science, 5(5): 731–742. Turner, M.G., Baker, W.L., Peterson, C.J. and Peet, R.K. (1998). Factors influencing succession: Lessons from large, infrequent natural disturbances. Ecosystems, 1: 511–523. Turner, N.J., Davidson-Hunt, I.J. and O’Flaherty, M. (2003). Living on the edge: Ecological and cultural edges as sources of diversity for social-ecological resilience. Human Ecology, 31(3): 439–461. Urban, F.E., Cole, J.E. and Overpeck, J.T. (2000). Influence of mean climate change on climate variability from a 155-year tropical Pacific coral record. Nature, 407: 989–993. Van Wagner, C.E. (1978). Age-class distribution and the forest fire cycle. Canadian Journal of Forest Research, 8: 220–227. Van Wagner, C.E., Finney, M.A. and Heathcott, M. (2006). Historical fire cycles in the Canadian Rocky Mountain parks. Forest Science, 52(6): 704–717. Varem-Sanders, T.M.L. and Campbell, I.D. (1996). Dendroscan: A tree-ring width and density measurement system. Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, AB, Canada. 131 p. Veblen, T.T. (1992). Regeneration dynamics. In: Glenn-Lewin, D.C., Peet, R.K. and Veblen, T.T. (eds.). Plant succession: Theory and prediction. Chapman and Hall, London, UK. pp. 152–187. Veblen, T.T. (2003). Historic range of variability of mountain forest ecosystems: Concepts and applications. The Forestry Chronicle, 79(2): 223–226, doi:10.5558/tfc79223-2. Veblen, T.T. and Kitzberger, T. (2002). Inter-hemispheric comparison of fire history: The Colorado Front Range, U.S.A., and the Northern Patagonian Andes, Argentina. Plant Ecology, 163: 187–207.  131  Veblen, T.T., Kitzberger, T. and Donnegan, J. (2000). Climatic and human influences on fire regimes in ponderosa pine forests in the Colorado Front Range. Ecological Applications, 10(4): 1178–1195. Wadleigh, L. and Jenkins, M.J. (1996). Fire frequency and the vegetative mosaic of a spruce-fir forest in northern Utah. Great Basin Naturalist, 56(1): 28–37. Wang, H., Schubert, S., Suarez, M. and Koster, R. (2010). The physical mechanisms by which the leading patterns of SST variability impact U.S. precipitation. Journal of Climate, 23: 1815–1836, doi: 10.1175/2009JCLI3188.1. Wang, T., Hamann, A., Yanchuck, A., O'Neill, G.A. and Aitken, S.N. (2006). Use of response functions in selecting lodgepole pine populations for future climates. Global Change Biology, 12: 2404–2416. Wang, T., Hamann, A., Spittlehouse, D.L. and Murdock, T.Q. (2012). ClimateWNA–High-resolution spatial climate data for western North America. Journal of Applied Meteorology and Climatology, 51: 16–29. Watson, E. and Luckman, B.H. (2001a). Dendroclimatic reconstruction of precipitation for sites in the Canadian Rockies. Holocene, 11: 203–213. Watson, E. and Luckman, B.H. (2001b). The development of a moisture-stressed tree-ring chronology network for the Southern Canadian Cordillera. Tree-Ring Research, 57: 149–168. Watson, E. and Luckman, B.H. (2002). The dendroclimatic signal in Douglas-fir and ponderosa pine tree-ring chronologies from the Southern Canadian Cordillera. Canadian Journal of Forest Research, 32: 1858–1874. Watson, E. and Luckman, B.H. (2004). Tree-ring based reconstructions of precipitation for the Southern Canadian Cordillera. Climatic Change, 65: 209–241.  132  Watson, E. and Luckman, B.H. (2005). Spatial patterns of preinstrumental moisture variability in the Southern Canadian Cordillera. Journal of Climate, 18: 2847–2863. Westerling, A.L. and Swetnam, T.W. (2003). Interannual to decadal drought and wildfire in the western United States. EOS, Transactions American Geophysical Union, 84(49): 545–560. Westerling, A.L., Hidalgo, H.G., Cayan, D.R. and Swetnam, T.W. (2006). Warming and earlier Spring increase western U.S. forest wildfire activity. Science, 313: 940–943, doi:10.1126/science.1128834. Westhaver, A., Revel, R.D. and Hawkes, B.C. (2007). Firesmart®-ForestWise: Managing wildlife and wildfire risk in the wildland/urban interface-a Canadian case study. USDA Forest Service Proceedings, RMRS-P-46CD: 347–365. White, C.A. (1985). Wildland fires in Banff National Park, 1880–1980. Parks Canada, Canadian Department of the Environment, Ottawa, ON, Canada. 106 p. White, P.S. and Pickett, S.T.A. (1985). The ecology of natural disturbance and patch dynamics. Academic Press, San Francisco, CA, USA. 472 p. White, P.S., MacKenzie, M.D. and Busing, R.T. (1985). Natural disturbance and gap phase dynamics in southern Appalachian spruce–fir forests. Canadian Journal of Forest Research, 15: 233–240. Whitlock, C., Shafer, S.L. and Marlon, J. (2003). The role of climate and vegetation change in shaping past and future fire regimes in the northwestern US and the implications for ecosystem management. Forest Ecology and Management, 178(1-2): 5–21, doi:10.1016/S0378-1127(03)00051-3. Wierzchowski, J., Heathcott, M. and Flannigan, M.D. (2002). Lightning and lightning fire, central cordillera, Canada. International Journal of Wildland Fire, 11: 41–51, doi:10.1071/WF01048.  133  Wirth, C., Lichstein, J.W., Dushoff, J., Chen, A. and Chapin, F.S. (2008). White spruce meets black spruce: Dispersal, postfire establishment, and growth in warming climate. Ecological Monographs, 78: 489–505, doi: 10.1890/07-0074.1. Wong, C.M. and Lertzman, K.P. (2001). Errors in estimating tree age: Implications for studies of stand dynamics. Canadian Journal of Forest Research, 31: 1262–1271, doi:10.1139/cjfr-31-7-1262. Woodhouse, C.A. (1993). Tree-growth response to ENSO events in the central Colorado Front Range. Physical Geography, 14: 417–435. Wright, C.S. and J.K. Agee. (2004). Fire and vegetation history in the eastern Cascade Mountains, Washington. Ecological Applications, 14(2): 443–459. Wyatt, M.G., Kravtsov, S. and Tsonis, A.A. (2011). Atlantic Multidecadal Oscillation and Northern Hemisphere’s climate variability. Climate Dynamics, 38: 929–949, doi:10.1007/s00382-011-1071-8. Yu, J. and Kim, S.T. (2013). Identifying the types of major El Niño events since 1870. International Journal of Climatology, 33: 2105–2112, doi: 10.1002/joc.3575. Zhang, Y., Wallace, J.M. and Battisti, D. (1997). ENSO-like interdecadal variability: 1900–93. Journal of Climate, 10: 1004–1020. 

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