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Post-fire regeneration : a spatial and temporal study of tree and vegetation regeneration Leclerc, Marie-Eve 2016-04

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        POST-FIRE REGENERATION: A SPATIAL AND TEMPORAL STUDY OF TREE AND VEGETATION REGENERATION     Marie-Eve Leclerc  FRST 497 April 2016   1  Abstract  Climate change and fire suppression are both important factors in the future of our forests. With drier longer summers, higher fuel loads and denser stand structures, fire risks are imminent. Understanding the dynamics of a growing forest could potentially lead to more efficient reforestation of disturbed sites. At Knife Creek a study was undertaken to spatially and temporally compare vegetation and tree seedling composition between plots that burned at moderate and high severity in contrast to control plots that did not burn. It was found that paper birch, Douglas-fir and trembling aspen have success at establishing the growing season immediately following a fire. The species composition varied across all burn types as well as their dominance. In 2014, the moderate burn sites had the highest diversity, and the control sites had the highest Uncertainty. In 2015, the high burn sites had the highest diversity and the moderate sites the highest Uncertainty.    Key words: Diversity, germinants, post-fire, regeneration, richness, seedlings, vegetation     2   Table of Contents   Abstract…………………………..…………………………………....………………….………..1  Introduction……………..………………………………………….………………………….…3  Methods……………..…………………………………………………………………...…………4  Results & Discussion……………………………………………………………………….....6  Literature Cited………………………………………………………………………...……..18  Appendix………………………………………………………………………………...………20   3  Introduction  A changing climate will undoubtedly impact the existing forests by changing long term weather patterns that have taken the forests years to adapt to overcome disturbances. Potential long term effects of climate change include a shift in moisture levels (Heyerdahl, Brubaker & Agee, 2002); earlier snowmelts leading to longer fire seasons and increasingly extreme summer droughts drying out more fuels (Miller, Safford, Crimmins & Thode, 2009). Not only are there changing climate trends that could influence fire disturbances but there are also other factors like the changes in stand structure and fuel load since the application of fire suppression (Heyerdahl et al., 2002). With fire suppression, fuels have accumulated (Filmon, 2003), leading to a shift in the natural disturbance regime for which these ecosystems have been adapted tp (Odion, Moritz & DellaSala, 2010), increasing the risk of fire spread and intensity. In a study by Miller, Safford, Crimmins and Thode (2009), they found there was a higher frequency of fire starts, with more stand-replacing fires burning at higher severities with higher patch sizes. Fire suppression mixed in with climate change, will lead to more natural disturbances on the landscape; triggering natural regeneration. Understanding the dynamics of a growing forest could potentially lead to more efficient reforestation of disturbed sites.   A wildfire at the Alex Fraser Research forest in 2013 gave the opportunity to quantify natural regeneration of trees and understory vegetation over the next two growing seasons. The fire was 6ha in size and burnt through a pre-commercially thinned stand and resulted in some areas of high-severity and moderate-severity effects. This study’s objectives were to: (1) spatially compare vegetation and tree seedling composition between plots that burned at moderate and high severity in contrast to control plots that did not burn; and (2) temporally compare changes in composition over a period of two growing seasons immediately following the fire. Few studies have reported on post-fire dynamics in the forests of British Columbia.  4  Therefore, a better understanding of vegetation succession and tree regeneration dynamics after disturbance by fire was achieved from this study.  Methods STUDY SITE The Knife Creek block is a 3487 ha plot of land located near 150 Mile House, British Columbia and is next to the San Jose Valley (Alex Fraser Research Forest, 2016). It predominantly is located in the Very Dry Mild (IDFxm) and Dry Cool (IDFdk) subzones of the Interior Douglas-fir biogeoclimatic zone.  From 1981 to 2010, mean annual temperature was 4.5±0.9°C and total annual precipitation was 308±177mm at Williams Lake, the nearest climatic station (52°10'59N 122°03'15W 940masl; Environment Canada 2015). Maximum monthly precipitation is in June and July, but is less than 60mm per month, typical of a summer-dry cool temperate climate. Being located in the dry subzones of the IDF zone, this area has a disturbance regime that was historically dominated by frequent stand-maintaining fires and infrequent stand-replacing fires (Province of British Columbia, 1995). The topography is mostly flat with some rolling hills (Alex Fraser Research Forest, 2016). The forest is mostly composed of interior Douglas-fir (Pseudotsuga menziesii) with a small portion of lodgepole pine (Pinus contorta), paper birch (Betula papyrifera) and trembling aspen (Populus tremuloides).  DATA COLLECTION I collected data in the summer of 2014 assisted by one individual and in the summer of 2015 by a crew of five individuals. Using a stratified-random research design, a total of 18 sites were sampled. Three were within high severity burn sites, nine within moderate severity burn sites and six controls were established on the outskirts of the burn. Within each of these sites, three circular satellite plots with an area of 16m2 were established five metres from plot centre at 360°, 120° and 240°. Within each satellite plot, the percent ground cover was visually estimated and recorded, (rock, woody debris, forest floor and soil). In this study, forest floor was  5  defined as anything that is organic matter such as needles and leaves and soil is defined as exposed mineral soil.  The regeneration of tree species was identified, tallied and sorted into three size categories: germinants <5cm, small seedlings 5-20cm and large seedlings 20-100cm.  The species of herbs, shrubs, mosses and grasses were identified and percent cover was estimated.  DATA ANALYSIS For each site for both 2014 and 2015, the mean and standard errors for the three satellite plots were calculated for substrate cover (mineral soil, forest floor, rock and coarse woody debris), the number of germinants, small and large seedlings and several vegetation attributes.  Vegetation cover was calculated for individual species and species grouped by life form as grasses, herbs, mosses and shrubs. . A species count was made for every plot to assess richness and an estimate of each species’ cover to assess the range of cover. The lowest value for cover was subtracted from the highest value for cover to assess for evenness.     Simpson and Shannon-Weiner’s indices take into account species richness and evenness and were calculated for each plot, and then averaged to represent species diversity and uncertainty in each satellite plot (Barbour, Burk, Pitts, Gilliam & Schwartz, 1999).  Simpson’s index was used to calculate diversity (D) using the following formula: 𝐷 = 1 −∑𝑝𝑖2𝑠𝑖=1  Pi being the proportion of all individuals in the sample (Barbour, Burk, Pitts, Gilliam & Schwartz, 1999). This diversity index takes into account richness and evenness of the species composition and reflects dominance by giving more weight to the abundant species compared to the rare species (Barbour, Burk, Pitts, Gilliam & Schwartz, 1999). The diversity index emphasizes the abundance measured as percent cover of each species and correlates inversely with dominance among  6  species. High numbers of species that have similar cover in a site result in the higher diversity values.  Uneven cover with high dominance by one or few species result in lower diversity values. Stable environments have lower diversity than patches disturbed at various times (Barbour, Burk, Pitts, Gilliam & Schwartz, 1999).  Shannon-Weiner’s index was used to calculate uncertainty using the following formula: 𝐻′ =∑ 𝑝𝑖𝑠𝑖=1ln 𝑝𝑖   The more variable the species composition of a community, the greater the uncertainty values (Barbour, Burk, Pitts, Gilliam & Schwartz, 1999).   For each variable, visual comparisons between fire severity classes as well as between both years were made using bar graphs.  For germinants, the number of individuals was converted to a logbase of 10 value.  A two-way analysis of variance (ANOVA) was used to compare means of each variable between the different fire severity classes, between the two years and potential interactions between them. For all statistical tests,  = 0.05.  Results & Discussion SUBSTRATE  Exposed mineral soil was most common immediately following fire but significantly decreased by the second year of sampling. In 2014, the percent cover of exposed mineral soil ranged from 78% to 87% on the burned sites (Figure 1A) and in 2015 it dropped to 4% to 30% (Figure 1B-C).  It was significantly higher on the burned sites than the control sites, but did not differ between the sites ranged as high and moderate burn severity (Figure 2A). Conversely, forest floor cover ranged from 3% to 7% in 2014, making it significantly less than the control sites (Figure 2B). The following year, there was a significant increase of forest floor cover to 54%-70% on  7  the burn sites and consequently a significant decrease of mineral soil cover. Coarse woody debris had no significant change (Figure 2C) and rock cover significantly increased (Figure 2D)  The substrate cover indicates the effects of the 2013 fire, which included both surface and crown fire (Luu 2014). In the summer of 2014, the first growing season after the fire, the soil in the disturbed sites was largely exposed mineral soil, with most of the forest floor debris burnt from the fire The following year, after a year of growth, leaf litter accumulate from deciduous plants, as well as needles and woody debris falling from the fire-affected trees, the amount of organic material on the forest floor increased in cover, including leaf litter and coarse woody debris.  GERMINANTS, SMALL SEEDLINGS AND LARGE SEEDLINGS The number of germinants varied among species and fire severities and between years. Paper birch had the most germinants on the burn sites with 313,329 and 169,236 germinants/ha in 2014 and 2015, respectively (Figure 3A-F). Between burn severities, the moderate sites had significantly more paper birch than the high burn site (Figure 4A-C). In 2014, Douglas-fir germinants were regenerating in the burned and control sites (Figure 3A-F) but predominantly on the burn sites with no significant difference between the high burn and moderate burn sites, 15,486 seedlings/ha and 19,838 seedlings/ha respectively (Figure 4D-F). From 2014 to 2015, there was a significant loss from 15,486 to 8,958 seedlings/ha on the high burn sites and 19,838 to 12,083 seedlings/ha on the moderate burn sites for Douglas-fir (Figure 4D). In 2015, trembling aspen began to regenerate on the high burn sites (Figure 3A-F) with 1,528 seedlings/ha which was significantly more germinants than the moderate sites (Figure 4G-I). Meanwhile, the number of Douglas-fir and paper birch germinants decreased at the burned sites by 42% and 39% for high and moderate sites for Douglas-fir and by 42% and 46% for high and moderate sites for paper birch (Figure 3A-F).    8  The regeneration of small seedlings was very different from the germinants between burn intensity sites and species. Trembling aspen had the most small seedlings in 2014 in the high burn site with approximately 3000 seedlings/ha on average (Figure 5A-C), significantly more than the moderate burn sites (Figure 4G-I). Douglas-fir small seedlings were only present in the control sites at 729 seedlings/ha (Figure 5A-C). 2015 showed a surge of paper birch seedlings on the high burn sites with an average of 1181 seedlings/ha and 2593 seedlings/ha on the moderate burn sites compared to the lack of regeneration in 2014 (Figure 5A-C).   There was minimal large seedling regeneration. In the large seedlings, there were 104 Douglas-fir seedlings/ha on average in the control areas initially in 2014 and decreased to 35 seedlings/ha in 2015 (Figure 5 D-F). In 2015, there were 70 Douglas-fir seedlings/ha that entered this size in the moderate burn sites (Figure 5D-F). No other species’ seedlings entered this size class.  Douglas-fir and paper birch established germinants successfully and immediately following fire due to their optimal growth being on mineral soil (Safford, Bjorkbom and Zasada, 1990; Hermann and Lavender, 1990). Paper birch is among one of the first species to reforest areas that have been burnt (Farrar, 1995), and regenerate by vegetatively sprouting from surviving roots following disturbances such as fire (Safford, Bjorkbom and Zasada, 1990), facilitating the regeneration process. Douglas-fir is well adapted to wildfire and has a high potential for natural regeneration in open areas with dry climates, especially following wildfires (Klinka et al. 1999). Paper birch had significant more successful germinants on the moderate burn sites potentially from the coverage from neighbouring canopy trees. The moderate sites had more live trees with foliage (Luu 2014) and could potentially have provided cover for the soil and maintained a higher moisture content than the high burn sites. The added cover also provided extra shade; paper birch thrives in shaded areas over full-sun sites (Safford et. al, 1990).     9  Douglas-fir did not have a significant difference between sites that burned at moderate and high severity, although it requires protection on dry and warm sites, it is not as sensitive to open areas as paper birch perhaps because it has a higher tolerance to heat (Klinka., Worrall, Skoda, Varga, & Krajina, 1999). Despite not having a significant difference between high and moderate burn sites, Douglas-fir had more germinants on the moderate sites (Figure 6G). Seed masting for Douglas-fir has been recorded to occur every 1-3 years (K.Day, personal communications, Nov 19. 2015). It was noted that 2013 was a heavy seed crop year across the IDF. Many foresters reported a “very high year” for seed cones (M. Waterhouse, personal communications, Feb 16. 2016), as well as visually assessed as “high” in trials in the IDFxm (Waterhouse, & Daintith, 2016). There has also been observations of increasing bumper seed years from hot and dry summers in the region (K.Day, personal communications, Nov 19. 2015). Additionally the stand had just undergone juvenile spacing, provding more open space, providing more light for the germinants (K.Day, personal communications, Nov. 19, 2015).   A significant decrease in Douglas-fir in germinants from 2014 to 2015 could be attributed to the germinants growing and moving into the next two size classes or mortality due to the overall increase cover of grasses and herbs (Figure 6A-C). The grasses compete for moisture, increases the level of shade to an intolerable level, leaves from herbs can smother the seedlings and they are all additional competition for moisture (Hermann and Lavender, 1990). Additional competition for moisture may have been a contributing factor to the loss of paper birch, being more sensitive to water deficiency (Klinka., Worrall, Skoda, Varga, & Krajina, 1999). Also, best germination for paper birch occurs on mineral soil and greatly diminishes on humus and undisturbed liter (Safford, Bjorkbom and Zasada, 1990). In the case of paper birch, these losses from the <5cm size class cannot be only attributed to death, but might be due to the germinants growing and entering the next height class. For all changes through time, any positive gains demonstrate that new establishments are greater than mortalities.   10  Trembling aspen had the fastest growth of all small seedlings in 2014 and already was in a higher size class; they grow quickly in their first year of germination (Perala, 1990). The high growth rate on the burn sites could be due to the seedlings developing a long tap root (Perala, 1990), accessing water from a lower water table, as well as the increased light reaching the ground from the reduced canopy (Luu, 2014). Additionally, trembling aspen is a sucker and can also be sustained by the parent root system, receiving all the water and nutrients needed for growth (Perala, 1990). In 2015, there are germinants in addition to small seedlings potentially due to the decrease in optimal mineral soils for germination and due to an increase of coverage from grasses; although trembling aspen does not require light for germination, it does for secondary growth (Perala, 1990)  Paper birch grew into a new size class in 2015, with an increase in humus availability, providing more nutrients and facilitating secondary growth (Safford, Bjorkbom and Zasada, 1990).  The first year of growth for Douglas-fir can be slow due to moisture limitations which can trigger dormancy in midsummer (Hermann and Lavender, 1990), which is possibly reflected in the lack of small and large seedlings (Figure 5 E-I). However, in the control site, small and large seedlings were recorded, most likely which predate the fire and not recorded in the first year of data collection.( Figure 5H-I). However, these could have potentially had very favourable microsites with increased tree protection, or vegetation cover, allowing for fast growth, which is possible in their first 5 years (Klinka., Worrall, Skoda, Varga, & Krajina, 1999).  When assessing the germinant and seedlings, it is difficult to differentiate whether a decrease in one size class means the new establishments grew into a new age class, or if it’s mortality. Additionally, for germinants in the middle height class, it is difficult to identify if these seedlings were germinants previously and grew into the class or if they are very fast growing new establishments.    11   VEGETATION The different sites all had similar species but did not share the same composition. The moderate severity sites had the most species overall with 36 in 2014 and 40 in 2015 (Table 1). The high severity sites had the least species overall with 20 and 27 in both 2014 and 2015 respectively (Table 1). On the high severity sites, there was a species increase from 2014 to 2015 for shrubs and mosses from 4 to 6, and herbs from 10 to 16 (Table 1). The moderate sites saw an increase of 2 species for herbs and 1 for both mosses and shrubs (Table 1),  Table 1 Total species count sorted for each site type and growth form  2014 2015 High Severity Moderate Severity Control High Severity Moderate Severity Control Grass 2 3 2 2 3 2 Moss 4 7 9 6 8 10 Herb 10 20 11 16 22 19 Shrub 4 7 9 6 8 10 Total 20 36 29 27 40 38   In both 2014 and 2015 there were species only found on the burn sites, the species with the highest percent cover being Epilobium angustifolium, Marchantia polymorpha and Ceratodon purpureus. There were species that were also only found on the control sites, the species with the highest percent cover being Dicranium polysetum, Hylocomium splendens and Rhytidiadelphus triquetrus. Some species were only found on control sites in 2014, but by 2015 they were found on the moderate sites such as: Vaccinium caespitosum, Lilium columbianum, Goodyera oblongifolia. Agoseris glauca and Agrostis gigantean was a new species found on both moderate and control sites only in 2015. Sonchus arvensis, Rubus ideaeus and Cirsium arvense  12  were new in the high severity burn. Viola adunca, was only present on certain moderate sites in 2014 and only present on other moderate sites in 2015 in different plots. This was also the case for Fragaria virginiana and Vicia Americana. Calamagrostis sp. was consistently found on all site types.   Some species dominated the sites and is apparent with high evenness values. The high severity sites had the lowest total spread in cover between species with 120 in 2014, and 158 in 2015 (Table 2). The control sites had the highest total spread with 176 and 172 in 2014 and 2015, respectively (Table 2).   Table 2 The range of species cover and summed spread, sorted for each site type and growth form   2014 2015 High Severity Moderate Severity Control High Severity Moderate Severity Control Grass 1-66 1-39 1-47 1-59 1-54 1-69 Moss 1-10 1-49 1-91 1-34 1-29 1-64 Herb 1-44 1-26 1-6 1-64 1-76 1-19 Shrub 1-4 1-12 1-36 1-5 1-7 1-24 Total 120 122 176 158 162 172  In 2014, grasses dominated the high severity sites with an evenness value of 66 followed by herbs (Table 2) and consequently had the highest cover among life forms and site types (Figure 6A). In 2014, Calamagrostis sp. had a cover of up to 70% and Epilobium angustifolium‘s highest cover was 45%. In 2015, Calamagrostis sp.had a cover up to 60% and Epilobium angustifolium increased to 65%, making the herbs have the highest evenness value with 64 and increased the overall grass and herb cover (Figure 6B-C). Ceratadon purpureus and Marchantia polymorpha increased in cover, increasing the overall moss cover from 4% to 8% (Figure 6C) but  13  the increase remained insignificant (Figure 7A-D). Shrubs increased insignificantly in cover (Figure 7A-D) in 2015 by less than 1%.  Mosses had the most cover on the moderate sites with an evenness value of 49 followed by grasses with 39, in 2014. The moderate severity sites were dominated by Marchantia polymorpha and Calamgrostis sp. with the highest cover being 50% and 45%, respectively. In 2015, herbs had the highest cover in the moderate severity sites with 76, dominated by Epilobium angustifolium. Shrubs decreased by less than 1% in cover (Figure 6C).   On the control sites, Pleurozium schreberi dominated followed by Calamagrostis sp in both years. Pleurozium schreberi highest cover was 92% in 2014, resulting in a high evenness value of 91 for mosses in 2014, and 63 in 2015 (table 2), Calamagrostis sp. highest cover was 50% in 2014 and 70% in 2015, leading to the highest evenness values of 69 (Table 2). Overall, the control sites had the highest cover for grasses and mosses, which increased from 17% to 34% for grasses and 15% to 17% for mosses (Figure 6C) The control sites had the highest vegetative cover by a significant amount for mosses and shrubs, but not for herbs where it was significantly lower, and grasses where there was no significant difference (Figure 7A-D). On the control sites, there was an increase in the number of both herb and shrub species (Table 1) despite there being a decrease in cover for shrubs by 1.5% (Figure 6C).   Throughout all the sites, Epilobium angustifolium maintained the same density from one summer to the next, however, there was an increase in the number of herb species present. In all sites, herbs provided the highest number of species followed by shrubs despite having the lowest cover. Generally, Spirea betufolia and Arctostaphylos uva-ursi decreased in cover and the diversity of shrubs existing in 2015 saw a decrease.    14  The overall values for both diversity and uncertainty among the sites were similar (Figure 8-9).The moderate severity burn sites had the highest diversity at 0.68 in 2014, with also the lowest difference in cover between species on average for both years with a range of 21 in 2014.Following the moderate sites, the control sites had a diversity value of 0.66 and the highest difference in cover for both years, with a range of 49 (Figure 10), and the most number of species per site with an average of approximately 12 (Figure 11). There were no significant differences in diversity (Figure 12). The control sites had significantly higher evenness values (Figure 13). The level of uncertainty was the highest in the control site in 2014 with a value of 1.51 (Figure 9).  However, the following summer, the moderate severity had the lowest diversity value at 0.63 (Figure 8), but increased to the highest Uncertainty value of 1.53 (Figure 9), with an increased difference among species cover to 33 in 2015 (Figure 10) and in richness by three species (Figure 11). Overall, 2015 was significantly richer (Figure 14). The control sites and the high burn sites had the least change in diversity from 2014 to 2015 with an insignificant <0.01 change in value (Figure 12) and also an insignificant increase in Uncertainty (Figure 15).  The site’s diversity immediately after the fire, forms a bell shaped curve; the amount of diversity peaks on the moderate sites in 2014 (Figure 7). This reflects Huston’s (1979) explanation of natural diversity, the “intermediate disturbance hypothesis.” The theory states that at a certain frequency of disturbance, the diversity of species will be greater than at equilibrium; post disturbances, diversity increases with time up to a point, then dominance by a few long-lived, large-sized species reverses the trend and diversity falls thereafter (Barbour, Burk, Pitts, Gilliam & Schwartz, 1999). Too frequent or intense disturbances will initially lower species diversity, as seen in the high severity burn site (Figure 7) but an optimal disturbance severity or intensity maximizes diversity, as it does on the moderate severity burn sites. Diversity is most influenced by cover abundance, so plots with a higher species  15  count but with a few species with a really high abundance will have a lower calculated diversity than a plot with a smaller species count but with a less of a divide between species’ cover. The moderate burn sites had the most even cover between all species on average, and highest total species count, resulting in the highest diversity value in 2014 and Uncertainty value in 2015.  The results suggest that at equilibrium, there are a few key species with a high dominance, mixed with a low percent cover of an abundant number of species; the control sites are the closest to being in equilibrium and in both years, had the highest values for richness and evenness. Initially following a disturbance, only some species are adapted to grow on less than favourable conditions, such as Calamagrostis sp. which is a “very aggressive colonizer after disturbances” (Pojar & Mackinnon, 1994, p. 321). The transition of species from one site type to the next can almost be seen as seral stages in a forest. For example, the high severity burn site had the highest moss gain over a year because Ceratodon purpureus and Marchantia polymorpha both thrive on mineral soil (Pojar & Mackinnon, 1994) but these species weren’t found on control sites due to different site conditions. As the site conditions change, a different species compostition emerges. Huston (1979) explains certain species being present immediately after a disturbance that are not present when the site is at equilibrium and vice versa; “r-selected” taxa are present in locally favorable microsites and “k-selected” taxa are present at equilibrium. With more frequent disturbances, “k-selected taxa” decrease and at equilibrium, “r-selected taxa” decrease. When the optimum disturbance frequency or intensity is achieved, then the maximum amount of “r” and “k” selected taxa are present. In these plots, Epilobium angustifolium, Ceratodon purpurus and Marchantia polymorpha could be “R-selected species” and Dicranium polysetum, Hylocomium splendens and Rhytidiadelphus triquetrus could be “K-selected species”.   Over time, both the high and moderate sites show a growing gap between species evenness, suggesting that a few key species begin to dominate the cover, until an equilibrium is met. In 2015, the dominant species on the moderate sites (Epilobium  16  angustifolium and Calamagrostis sp.) increased in cover, creating a bigger difference between the dominant species and the others, possibly making it difficult for shrubs to grow due to these long, tall grasses and herbs shading them, leading to a lower diversity value. Conversely, the Uncertainty index does not weigh abundance as heavily as Simpson’s index and has the highest value for the moderate site in 2015 (Figure 9). In 2015, the high severity burn sites also increased in uncertainty (Figure 10), reflecting the increasing trends in both evenness and richness (Figure 10 & 11). Although the control sites had an increase in species count from 2014 to 2015, it had only one main species increasing in cover, Calamagrostis sp .to which diversity and Uncertainty decreased. The high severity burn sites saw an increase in diversity due to the vegetation cover of more than just the dominant species increasing.  Conclusions & Recommendations Disturbances play an important role in shaping the landscape, variation such as intensity and severity create the nuances within each ecosystem. The Knife Creek fire provided the opportunity to compare the tree and vegetative growth following both a crown and surface fire as well as observe the changes the regeneration undergoes over the period of two growing seasons.   The growing season immediately following the fire, Douglas-fir, paper birch and trembling aspen grew back, having adaptations to fires and growing best on bare mineral soil; paper birch had the most germinants on the moderate burn sites, whereas the trembling aspen had the smallest seedlings on both burn sites. The second growing season lead to the decrease of germinants but to an influx of small seedlings as the Douglas-fir and paper birch germinants grew or possibly mortality. Trembling aspen saw a decrease in small seedlings from mortality.   The vegetative regeneration had many overlapping species across the control, high and moderate severity sites, however the cover was not necessarily the same. Epilobium angustifolium was prominent on the burn sites but not on the control.  17  However, Calamagrostis sp. was a dominant species across all three site types. The moderate sites had the highest diversity in 2014 and the control sites had the highest Uncertainty. But in 2015, the high severity burn site had the highest diversity from being the site with the least increase in evenness value, and moderate burn sites has the highest Uncertainty.   These results are based on only two seasons of data and could be reflecting interannual variation rather than a long term trend. Other factors including weather could have impacted the regeneration of the sites.  Further data collecting should be done to confirm these trends. Additional plots and sites could also help calculate the diversity and Uncertainty indices as they were not a consistent trend across the plots, they varied greatly. Some increased from one year to the next, while others in the same sites notably decreased.     18  Literature cited  Alex Fraser Research Forest. (N.d.) About the Alex Fraser research forest. Retrieved  from  Barbour, M.G., Burk, J,H., Pitts, W.D., Gilliam, F.S., & Schwartz., M.,W. (1999).  Terrestrial Plan Ecology: Third Edition. Menlo Park, California: Benjamin/Cummings  Environment Canada. (2015). Canadian Climate Normals. Retrieved from  Farrar, J., L. (1995). Trees in Canada. Markham, Ontario: Fitzhenry & Whiteside  Limited.  Filmon G. (2003).  Firestorm 2003 Provincial Review.  Retrieved from  Hermann, R.K. & Lavender, D.P. (1990). Pseudotsuga menziesii. Pp. 527-540 in R.M.  Burns and B.H. Honkala (technical coordinators) Silvics of North America, Vol. 1. Agri. Handbook 654, USDA For. Serv., Washington, D.C.   Heyerdahl, E.K., Brubaker, L.B., & Agee, J.K. (2002).  Annual and decadal climate  forcing of historical fire regimes in the interior Pacific Northwest, USA. The Holocene, 12(5), 597-604. Retrieved from  Huston, M. A. (1979). A general hypothesis of species diversity. American Naturalist  113, 81-101.   Klinka, K., Worrall, J., Skoda, L., Varga, P., & Krajina, V.J. (1999). The distribution and  synopsis of ecological and silvical characteristics of tree species in British Columbia’s forests. 2nd edition. Coquitlam, BC: Canadian Cartographics Ltd.  Luu, V. (2014). An Analysis of Fire’s Direct and Indirect Effects on the IDFdk Zone.  Graduating Essay, Faculty of Forestry, University of British Columbia, Vancouver. 51p.  Miller, J. D., Safford, H.D., Crimmins, M., & Thode, A.E. (2009). Quantitative evidence  for increasing forest fire severity in the Sierra Nevada and Southern Cascade mountains, California and Nevada, USA.  Ecosystems, 12, 16-32.  DOI: 10.1007/s10021-008-9201-9  19   Ministry of Forests, Lands and Natural Resource Operations. (2012). Wildfire  Management Branch Strategic Plan 2012-2017. Retrieved from  Odion, D. C., Moritz, M. A., & DellaSala, D. A.. (2010). Alternative Community States  Maintained by Fire in the Klamath Mountains, USA. Journal of Ecology, 98(1), 96–105. Retrieved from  Perala, D.A. (1990). Populus tremuloides. Pp. 555-569 in R.M. Burns and B.H.  Honkala (technical coordinators) Silvics of North America, Vol 2. Agri. Handbook 654, USDA For. Serv., Washington, D.C.  Pojar, J., & MacKinnon, A. (1994). Plants of coastal British Columbia. Vancouver, BC:  Lone Pine Publishing  Province of British Columbia. (1995). Biodiversity Guidebook. Retrieved from   Safford, L.O., Bjorkbom, J.C., & Zasada, J. C. 1990. Betula papyrifera. Pp. 158-171 in  R.M. Burns and B.H. Honkala (technical coordinators) Silvics of North America, Vol 2. Agri. Handbook 654, USDA For. Serv., Washington, D.C   Waterhouse, M. & Daintith, N. (2016). Managing dry. Douglas-fir forests in central  British Columbia: The Farwell Canyon project: Year 10 stand dynamics. Draft.            20  Appendix                A)                                                                             B)                                                                               C)                                                                                                                                        Figure 1 Substrate cover in high and moderate burn sites and control sites in 2014 (A), 2015 (B) and a change in both years (C)     Percent Cover (%)  21  A)                                                                                                                                  B)                                             C)                                                                                                                                      D)                                             Figure 2 Significant differences of substrate covers between 2014-2015 and different burn site Percent Cover (%)  22    A)                                                                B)                                                                     C)                             D)                                                                       E)                                                                        F)   Figure 3 Germinants <5cm  density (A-C) and logbase 10 of germinants <5cm density(D-F) Density (seedlings/ha) Density LogBase10(seedlings/ha)  23     A)                                                                B)                                                            C)               D)                                                                     E)                                                                    F)                          G)                                                                    H)                                                                     I)               Figure 4  The statistical significance between 2014-2015 and the different sites for  paper birch (A-C), Douglas-fir (D-F) and trembling aspen (G-I) Density (seedlings/ha)  24     A)                                             B)                               C)                              D)                                                               E)                                                             F)                Figure 5  Seedling density for small seedlings 5-20cm (A-C) and large seedlings (D-F)   Density (seedlings/ha)  25            A)                                                                              B)                                                                                C)         Figure 6  Vegetation cover in high and moderate burn sites and control sites in 2014 (A), 2015 (B) and a change in both years (C)         Percent Cover (%)  26   A)                                                                                                                               B)                                                C)                                                                                                               D)                                    Figure 7  Significant differences of vegetation cover between 2014-2015 and different burn types (A-D)Percent Cover (%)  27                                                     Figure 8 Calculated diversity for high, moderate burn sites and control sites               Figure 9 The average Shannon-Weiner index for high, moderate burn sites and control sites s                                                           Figure 10 Calculated evenness for species in high, moderate burn sites and control site          Figure 11 Average species count for high, moderate burn sites and control sites     28                                                         Figure 12 Significant difference in evenness between sites and years                                          Figure 13 Significant difference in evenness between sites and years                                                                   Figure 14 Significant difference in richness between sites and years                                           Figure 15 Significant difference in Uncertainty between sites and years 


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