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Responses of high Arctic sedge meadows to climate warning at Alexandra Fiord, Ellesmere Island, since… Hill, Geoffrey E. 2006

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Responses of High Arctic Sedge Meadows to Climate Warming at Alexandra Fiord, Ellesmere Island, since 1980 by Geoff Hill B.Sc, The University of British Columbia, 2002 A Thesis Submitted In Partial Fulfillment of The Requirements For The Degree of Master of Science in The Faculty of Graduate Studies (Geography) The University of British Columbia August 2006 ©Geoff Hill, 2006 ABSTRACT The global climate is changing rapidly and Arctic regions are showing strong responses to recent warming. Tundra response to climate change has been examined primarily through short-term experimental manipulations, which have not been corrobrated by long-term ambient change studies. I investigated changes in above and below ground biomass of wet sedge meadow communities to over two decades of ambient climate warming at Alexandra Fiord, Ellesmere Island, Nunavut, in the Canadian High Arctic (79° N). Above ground standing crop was harvested from five sedge meadow sites in the early 1980s and in 2005 using the same methods, and comparisons between years were made at site and species scales. Similar comparisons were made for below ground biomass at one site. Analysis of climate data from two permanent weather stations (Eureka and Resolute) and from automatic climate stations at the site, showed that over the past 35 years this region of the High Arctic has experienced an increase of ca. 0.7° C per decade in annual average temperature. There has been greater warming in the winter, with temperatures increasing by ca. 1 ° C per decade. Overall, both aboveground and belowground biomass had increased over the 25 year period. This increase is attributed to the warming climate since the 1980s as annual variation in net primary production was found to be insignificant over the period 1980-1984, despite large differences in annual climate. Dominant genera from each functional group showed significant positive response with increases in above and below ground biomass. Responsive genera include Car ex, Eriophorum, Dry as and Polygonum (Bistorta). Increased decomposition and mineralization rates, stimulated by air and soil warming, may have caused elevated productivity, as no differences in over-winter biomass or litter were found between sample periods. These results are validated by short-term experimental studies, conducted in other wet sedge tundra communities, which link fertilization with elevated decomposition, mineralization and tundra productivity. This study is, to my knowledge, the first to show responses in high arctic terrestrial systems to ambient climate change over the past twenty-five years. ii T A B L E O F C O N T E N T S A B S T R A C T i i T A B L E O F C O N T E N T S iii LIST O F T A B L E S iv LIST O F FIGURES v A C K N O W L E D G E M E N T S . vii C O - A U T H O R S H I P S T A T E M E N T viii 1. C L I M A T E C H A N G E AND T U N D R A RESPONSE 1 1.1. Introduction 1 1.2. Literature Review 1 1.2.1. Global Climate Change 1 1.2.2. Arctic Climate Change 2 1.2.3. Arctic Tundra 3 1.2.4. Tundra Response to Arctic Climate Change 3 1.3. Hypothesis 10 1.4. References 11 2. RESPONSES O F H I G H A R C T I C S E D G E M E A D O W S T O C L I M A T E W A R M I N G SINCE 1980 15 2.1. Introduction 15 2.2. Materials and Methods 18 2.2.1. Definitions 18 2.2.2. Study Site 18 2.2.3. Climate Analysis...... 18 2.2.4. Biomass and Soil Sampling 19 2.2.5. Statistics 21 2.3. Results and Discussion 23 2.3.1. Climate Analysis... 23 2.3.2. Sedge Meadow Response: Site A 28 2.3.3. Sedge Meadow Response: Sites B-E 36 2.3.4. Soil Responses 44 iii 2.3.5. Sedge Meadow Response to Winter Warming 44 2.3.6. Biomass / Carbon Dynamics , 45 2.4. References 47 3. Synthesis 52 3.1. Synthesis 52 3.2. Future Research 53 3.2. Tables .. . . 55 3.3. References 60 4. APPENDIX 61 4.1. Plot Dimensions 61 4.2. Additional Data 61 iv LIST OF TABLES Table 2.1. Correlation matrix of yearly average air temperature from 1991-1999 between climate stations at Resolute Bay, Cornwallis Island, Eureka, Ellesmere Island, AF Camp, Ellesmere Island, and AF Meadow, Ellesmere Island 26 Table 3.1. Correlation matrix (r) of point frame estimates with biomass / standing crop measurements from all plots 55 Table 3.2 Mean over-winter biomass and attached dead of species/groups ± standard error 56 Table 3.3. Mean peak above ground biomass and attached dead of species/groups, ± standard error 57 Table 3.4 Site A means of below ground biomass / standing crop ± standard error 59 Table 3.5. Soil pH 59 Table 4.1 a. Total point frame hits within a 50cm by 50cm frame with 5cm intervals (40 points/frame) 62 Table 4.lb. Total point frame hits within a 50cm by 50cm frame with 5cm intervals (40 points/frame) 63 Table 4.2. Plot Coordinates of all major plots at sites A, B, C, D, & E '. 64 s V L I S T O F F I G U R E S Figure 2.1 Alexandra Fiord, Ellesmere Island; an aerial photo from the southwest, with sites labeled A, B, C, D and E 19 Figure 2.2 Summer, yearly, and winter average mean daily air temperature from Resolute Bay, Cornwallis Island and Eureka, Ellesmere Island, from 1970 to 2005 24 Figure 2.3 Summer, yearly, and winter average mean daily air temperature from Alexandra Fiord Camp and Alexandra Fiord Meadow climate stations, from 1990-2001 and 1990-2003 respectively 25 Figure 2.4 Summer, yearly, and winter averaged mean daily soil temperature from Alexandra Fiord Meadow climate station, from 1993-2003 27 Figure 2.5 Site A over-winter above ground standing crop 29 Figure 2.6 Site A peak season above ground standing crop 30 Figure 2.7 Site A dominant species peak season above ground 31 Figure 2.8 Site A minor species peak season above ground 32 Figure 2.9 Site A moss and litter peak season above ground 33 Figure 2.10 Site A below ground standing crop 35 Figure 2.11 Site E over-winter above ground standing crop 37 Figure 2.12 Site B, C, D , E peak season above ground standing crop 38 Figure 2.13 Site B, C, D , E peak season above ground Carex spp.... 39 Figure 2.14 Site B, C, D , E peak season above ground Eriophorum triste and Dry as integrifolia 40 Figure 2.15 NMS of all plots in Site A 42 Figure 2.16 A NMS of all plots harvested for above ground standing & B crop in Site B, C, D , E 43 vi A C K N O W L E D G E M E N T S This M.Sc. thesis would not have been possible without baseline data and supervision provided by Henry GHR. This M.Sc. research was supported by grants to my supervisor, Dr. Greg Henry from NSERC, ArcticNet, and the Northern Scientific Training Program (NSTP), Dept of Indian and Northern Affairs Canada. Logistical support in the field was provided by the Polar Continental Shelf Project and the RCMP. My field assistants, Reed Moore and Sara Lebedoff, deserve many thanks for their help sorting tundra biomass and for their company over many sunny days and sunny nights at Alexandra Fiord. vii C O - A U T H O R S H I P S T A T E M E N T Chapter 2 of this thesis was co-authored with my thesis advisor Dr. Greg Henry. The sample design, data collection, analyses, and preliminary manuscript drafts were, however, completed with minimal input from Dr. Henry. v i i i 1. C L I M A T E C H A N G E AND T U N D R A RESPONSE 1.1. Introduction The global climate is currently changing at a rate unprecedented in the last 400 years (Overpeck 1997, Serreze et al. 2000, IPCC 2001). This literature review summarizes climate change at the global scale, and then narrows to Arctic regions and ecosystems, which are known to be highly sensitive to climate change. The objective of this literature review is to expose the dearth of and need for long term studies on the natural response of tundra to ambient climate variability and change. This research theme will be addressed and the chapter concluded with hypotheses and questions, which provide a foundation for Chapter 2. 1.2. Literature Review 1.2.1. Global Climate Change The Intergovernmental Panel on Climate Change (IPCC), the largest cooperative scientific endeavor conducted in history, published their 3 l d Assessment Report in 2001. The "Climate Change 2001: Synthesis Report", thoroughly reviewed the global impacts of climate change (IPCC 2001). They note a 0.6 ± 0.2 ° C increase in global mean temperature in the last 100 y, with the 1990s being the warmest decade of the millennium. With this warming trend, frost days have been reduced, the growing season has lengthened, and plant phenology has been accelerated. The warming trend noted is predicted to continue at 1.4-5.8 ° C during the 21st century; exceeding any previously recorded warming rate in the last 10,000 y. Warming trends are strongest at high latitudes due to feeback processes involving vast reservoirs and phase changes of ice and snow. When H 2 O changes from solid (ice or snow) to liquid (water) its albedo decreases from 75-95% to as low as 3% allowing one to two orders of magnitude more energy into the terrestrial or marine ecosystem (Wypych and Bokwa 2003). 1 1.2.2. Arctic Climate Change In-depth summaries on the impacts of climate change in Arctic regions have been completed by Serreze et al. (2000), the ACIA (2004) report, and Hinzman et al. (2005). All three sources report similar findings. The Arctic has warmed significantly over the last few decades, most notably in the spring and winter. The rates of warming are almost double those in lower latitudes and are predicted to increase 4-7 ° C in the coming century (ACIA 2004). UV light levels have also increased over the last few decades (ACIA 2004). Snow cover has decreased since 1972 (Serreze et al. 2000). Glaciers are retreating, especially those in sub-polar regions (Serreze et al. 2000). Sea, lake, and river ice extent and duration are decreasing (ACIA 2004). Permafrost has warmed from 2-4 ° C in the last century (Hinzman et al. 2005). Precipitation has increased by 8% in the last century (ACIA 2004). Ecotones including treeline and southern permafrost extent have shifted northward and are predicted to push northward hundreds of kilometers in the next 100 years (ACIA 2004). Disturbances including fire, species invasions, and hydrology changes will alter community composition and diversity (ACIA 2004, Hinzman et al. 2005). Indigenous cultures have changed and are expected to continue doing so as environmental changes become more apparent and widespread in the next century (ACIA 2004). Hinzman et al. (2005) paint a strong and clear picture of system wide response to Arctic climate change. They organized influential impacts into three categories. First order impacts stem from increasing thaw periods and increasing precipitation. Second order impacts result from a longer snow free season and greater winter insulation, which increase active layer depths and stimulate productivity. Tertiary impacts occur when animals respond to primary and secondary impacts. For example, the first order impact of lengthened growing season in northern Alaska has stimulated sedge productivity (2nd order impact), enriching the diet of lactating caribou, increasing the survival rate of young (3rd order impact) (Hinzman et al. 2005). However, Arctic systems are tightly coupled and counteractions and feedback processes exist at many levels (ACIA 2004). For example, winter warming can also enhance the formation of impenetrable ice lenses 2 under the snow, restricting access to the caribou's winter food supply (Hinzman et al. 2005). 1.2.3. Arctic Tundra Relative to other ecosystems on Earth, the tundra has received very little attention, due to its low human population density and logistical access barriers (Bliss et al. 1973). The first in-depth studies of tundra ecosystems occurred during the International Biological Program (IBP) in the early 1970s. In North America, the mean July position of the Arctic front is thought to regulate the northern extent of the treeline (Bliss et al. 1973). All land north of the treeline is considered Arctic. The Arctic has been divided into Low, Middle, and High classifications, based primarily on plant diversity and abundance (Polunin 1951). As latitude increases from the Low to High Arctic the influence of abiotic conditions outweighs biotic influences such as competition for sunlight or ground area (Polunin 1951). For example, Low Arctic vegetation can grow to two meters high, while High Arctic counterparts seldom exceed a few centimeters in height (Polunin 1951). Bliss et al. (1973) used the term "fragile" to define the relationship between tundra communities and their environment. This fragility exists in tundra communities due to: easily altered permafrost soils, low temperatures, short seasons (1-2 months in the High Arctic, and 3-4 months in the Low Arctic), frequent sudden synoptic weather changes in spring and fall, and low diversity with few redundant species (Bliss et al. 1973). 1.2.4. Tundra Response to Arctic Climate Change Studies of historical and paleo-environmental change have shown that during past periods of climate change, the tundra has responded by altering community structure and function (Ritchie 1984, Gajewski and Atkinson 2003). The tundra is strongly limited by temperature, moisture, and nutrients, all of which are interconnected (Bliss 1977). Low air and soil temperatures keep water in the solid phase for the majority of the year, which limits decomposition, mineralization, and plant growth. As air temperature and precipitation patterns change with climate change, soil temperature, growing season length, and nutrient availability can be indirectly affected. Changes in these variables can initiate community structure changes, often noted through ecotone shifts. In the last 3 century, both the tree-line and taiga-line have advanced northward in some regions and tundra extent is expected to retreat to the Queen Elizabeth Islands (Maxwell et al. 1997 and Serreze et al. 2000). Structural changes observed at smaller spatial scales include increased shrubbiness from aerial photo comparisons over the last 50 y (Sturm et al. 2001) and elevated productivity between 1981 and 1991 using Normalized Difference Vegetation Index (NDVI) from satellite imagery (Myneni et al. 1997). Functional changes include a switch from a terrestrial CO2 sink (30-100 g m"2 y"1), which has accumulated approximately 300 GT of carbon in the past 105 y, to a CO2 source at rates up to 150 g m"2 y"1 at study sites in northern Alaska (Serreze et al. 2000). With experimental manipulation of the tundra, Arctic research was able to move beyond observation, measurement, and inference, by isolating, controlling, and perturbing variables thought to be important in tundra response processes. These experiments began in earnest in the 1980s, in the laboratory, conducted over short time scales (<10° y). Elevated air temperature and CO2 concentrations in small chambers temporarily stimulated growth of tundra plants (Billings et al. 1984, Chapin and Shaver 1985, Oechel and Billings 1992). After a period of time, from days to weeks, the plants returned to their original growth rate, showing that other processes dominated at longer time scales. Field experiments, which manipulated environmental variables on longer time scales (1-19 y), were better able to induce vegetation responses that had relevance to observable community change, such as increasing shrubbiness from aerial photos, and to the scale of climate change (>10* y). The majority of manipulation experiments in North America have been centered around Toolik Lake, Alaska at the Long Term Ecological Research (LTER) site and at the International Tundra Experiment (ITEX) sites (Phoenix and Lee 2004). Most short term field experiments, lasting only a few years, have stimulated responses that have not been sustained through time, much like the laboratory tests described earlier. Arft et al. (1999) used meta-analysis to summarize the findings of 13 ITEX sites spanning four years of air warming with open top chambers (OTCs). They found a 4 consistent and significant vegetative growth response to warming in the second and third year of treatment, but a highly variable and non-significant fourth year across all functional groups and sites. This pattern was repeated within High Arctic sites and within the graminoid functional group. They were unable to determine if sample size or lagging resource deficiency reversed the trend in the fourth year. However, Arft et al. (1999) noted that their short term experiment did not account for the influence of warming on longer term ecosystem processes including decomposition and mineralization. Rolph (2003) confirmed that experimental warming with OTC's at Alexandra Fiord, Ellesmere Island, increased mineralization after ten years. She found significant increases in inorganic and organic nitrogen in warmed plots in wet tundra. Organic nitrogen, in the form of free amino acids, have been found to turn over rapidly, up to 20x per day, which places organic nitrogen in a more integral role in nutrient cycling than the less labile inorganic forms of nitrogen (Keilland 1995). Wet sedge species are able to utilize organic nitrogen (Chapin et al. 1992) Chapin et al. (1995), at Toolik Lake, AK, reported tussock tundra ecosystem responses three and nine years after experimental manipulations of temperature, nutrients and shading. They found short term (3 y) results to be poor predictors of longer term (9 y) responses, supporting what was summarized over smaller temporal scales but larger spatial scales by Arft et al. (1999). Chapin et al. (1995) also suspected that temperature manipulations over three years did not have a chance to influence soil processes including decomposition and mineralization. With similar results to Rolph (2003) they found measurable increases in soil nutrients after nine years of warming. After three years, above ground productivity of graminoids, non vascular plants, and deciduous shrubs increased (Chapin et al. 1995). However, six years later, only Betula nana, (a deciduous shrub) had sustained the increased productivity (Chapin et al. 1995). Additions of nitrogen and phosphorus, at 5-20 times the estimated annual requirement, enlarged the plant nutrient pool, directly stimulating growth more than any other treatment (Chapin et al. 1995). A reduction in light availability, caused by shading with translucent cloth, increased nutrients in the soil by shifting resource limitation from nutrients to light (Chapin et al. 1995). One of most often discussed findings of Chapin et 5 al. (1995) 's study (Henry 1997), is the matching response of control treatments to manipulated treatments, due to ambient climate change (Chapin et al. 1995). The control plots also showed an increase in dominance of Betula nana, which matched the treatment results (Chapin et al. 1995). The most recent meta-analysis of Low Arctic and alpine tundra responses to experimental manipulation, published by van Wijk et al. (2003), summarized 16 publications on all dominant plant community types near Toolik Lake, Alaska, and Abisko, Sweden. They addressed and supported the three main topics developed thus far in this literature review. (1) Nutrients are the strongest limiting resource in tundra ecosystems and stimulate the most vegetative response when enhanced. (2) Short term responses are not indicative of longer term responses. The relationship between time and growth response across treatments is non-linear at scales spanning days to decades. (3) Species respond individualistically and functional groups responses are often inversely correlated. Warming and fertilization together stimulated the most pronounced and significant response in productivity at both Toolik and Abisko (van Wijk et al. 2003). Warming, independent of fertilization, had much less effect, but was still significant. Deciduous shrubs and graminoids proved the most responsive across the plant community types accompanied by reductions in lichen and non vascular plants (van Wijk et al. 2003). They constrained their input data to experiments spanning more than three years, however most were between five and ten years, with only two out of 18 were greater than 15 years in duration. Walker et al. (2006) provide the most current meta-analysis of Low and High Arctic tundra responses to passive air warming from 11 ITEX sites. They consistently found increases in cover of deciduous shrubs and graminoids, supporting the findings of previous meta-analyses and site specific studies and experiments. They report losses in biodiversity after four years of warming, but due to the unpredictable response of originally dominant species, they were unable to provide predictions as to the future composition of tundra communities. Their results were biased towards communities on dry and mesic soils. 6 The contributions by Chapin et al. (1995), Arft et al. (1999), van Wijk et al. (2003), and Walker et al. (2006) addressed in detail the above ground responses to treatments, but did not adequately assess the soil processes and plant microbe interactions in the complex response of ecosystems to warming. Experimental warming has been shown to increase nutrient availability through elevated mineralization (Chapin et al. 1995, Rolph 2003), however, enhanced mineralization may not lead to a larger plant available nutrient pool if microbes are able to out-compete plants and immobilize nutrients into microbial biomass (Nadelhoffer et al. 1992, Schmidt et al. 1999). By comparing the short retention time of carbon in microbial biomass (<1 y) to the much longer retention times of N (>1 y) and P(>10 y), Jonasson et al. (1999a) showed that microbial biomass cycles nutrients tightly, leading to potential competition for nutrients with plant roots (Kaye and Hart 1997). Other studies have recorded negative net mineralization in the summer, when microbes are most active, and positive mineralization in the non growing season, supporting the hypothesis that microbes out compete plants for available nutrients. However, when tested with factorial manipulations of temperature, nitrogen and phosphorus, Jonasson et al. (1999b) found that microbial storage of N, P, or C did not increase with fertilization or warming, while tundra plants did increase their storage reservoirs, as shown in many previously mentioned studies, through increased biomass production. This study showed that tundra species were able to compete adequately for nutrients after fertilization (Jonasson et al. 1999b). Rolph (2003) also found microbial immobilization to not limit the growth of tundra species. It is clear that the Arctic is warming and the tundra is indirectly, but consistently, responsive to warming through elevated mineralization rates (Walker et al. 2006), a process which has the potential to enlarge the pools of available soil nutrients. Direct and indirect fertilization, through warming, consistently stimulate above ground productivity of deciduous shrubs, graminoids, and forbs after an initial and temporary variable response period. What still remains to be addressed in this review is the connection between carbon storage and the source of mineralized nutrients which stimulate tundra productivity. 7 Both Shaver et al. (1998), at Toolik Lake, AK, and Welker et al. (2004), at Alexandra Fiord, Nunavut, measured increases in gross ecosystem productivity (GEP) with experimental warming of wet sedge ecosystems. However, after nine years of OTC warming at Alexandra Fiord, and associated decomposition and mineralization enhancement, ecosystem respiration (Re) increased more than ecosystem photosynthesis (GEP), reducing net ecosystem carbon uptake (NEP) by ca. 20% (Welker et al. 2004). Shaver et al. (1998) found similar results: a combination of fertilization and warming reducing NEP by stimulating R e beyond GEP increases observed with increased biomass. Without investigation into R e, observed enhancement of above ground productivity would lead to postulations that the tundra was acting as a carbon sink. But with elevated R e from warming and fertilization it is apparent that organic matter was being decomposed faster than it was being produced (Mack et al. 2004). Mack et al. (2004) sought out the source of this volatilized carbon by analyzing soil carbon in long term treatment plots at Toolik Lake. They note relatively little decomposition of new litter inputs, and minor levels of root decomposition. By inference they conclude that decomposition of organic carbon deep in the soil column more than offset the above ground carbon sequestered after 20 y of experimental stimulation. Despite a doubling of above ground production, net ecosystem carbon losses were measured at ca. 2000 g m"2 (Mack et al. 2004). A review of tundra response studies has recently been conducted by Phoenix and Lee (2004). They summarize many of the papers and points made here. They also draw attention to: 1) the shortness of response studies, with most spanning less than 20 y; 2) the focus on summer manipulations, despite observations that winter warming has been much stronger than summer warming; and 3) the dearth of natural change studies. The majority of papers devoted to tundra response call for longer term experiments and longer term natural change studies in order to validate shorter term induced responses (Chapin et al. 1995, Chapin and Shaver 1996, Henry 1997, Arft et al. 1999, Johnson et al. 2000, Welker et al. 2004, Mack et al. 2004, Walker et al. 2006). Epstein et al. (2004) generated a model of vegetation response to climate change. Their model predicts that a 8 minimum of two decades of vegetative response to ambient warming may be required before above ground responses become measurable. Experimental control plots at Toolik Lake and other research stations are moving close to Epstein et al. 's (2004) 20 y mark, and will provide valuable validation and/or calibration information on experimentally induced responses. Long term natural change studies provide an alternative to two decades of control plot monitoring, but few have been conducted due to the lack of quality datasets greater than two decades old. Research in the Canadian Arctic was conducted as part of the International Biological Program in the 1970's and provides an excellent resource for repeat / comparison studies. For example, Mitchelutti et al. (2003) conducted a study at Char Lake, Cornwallis Is., Nunavut, with baseline IBP data, and found significant shifts in diatom communities that corresponded with climate change between 1968 and 2000. This type of repeat measure study is also feasible at Alexandra Fiord (AF) Ellesmere Island, Nunavut (78° 52'N, 75° 47'W), where Henry (1987, Henry et al. 1990) conducted his Ph.D. research on "The Ecology of Sedge Meadows" between 1980 and 1984 creating one of the Arctic's oldest datasets (Svoboda and Freedman 1994). Warming experiments were established a decade later at A F as part of the International Tundra Experiment (ITEX) (currently chaired by Henry, www, geog.ubc.ca/itex), creating one of the most appropriate sites to study long term tundra responses to ambient climate change. I investigated changes in above and below ground biomass and soil properties of wet sedge meadow communities to over two decades of ambient climate change at Alexandra Fiord, Ellesmere Island. By analyzing communities in wet soil conditions, the confounding factor of precipitation change was avoided. Comparisons were made at both the site scale, to determine the extent of sedge meadow responses, and at the species scale in order to understand responses influencing sedge meadow community structure. 9 1.3. Hypotheses The primary objective of this study was to make comparisons between samples measured in the early 1980s and again in 2005 at the site and species scale. At the site scale, I hypothesized that warming stimulated above ground sedge meadow productivity. At the species scale, I predicted increases in biomass of the two dominant graminoid species in the wet sedge meadows at Alexandra Fiord (Carex aquatalis stans and Carex membranacea). All valid comparisons are included in Chapter 2. The secondary objective was to ensure this study provided a solid foundation upon which future comparisons could be made. The initial concept for this thesis was drafted on the International Biological Programme's data set from Truelove Lowland, Devon Island, Nunavut. However, the data available were not valid for statistical comparisons. Changes in soil moisture are known to be as influential as changes in temperature when stimulating responses in tundra communities. However, I assumed that due to the saturated nature of wet sedge meadows, changes in precipitation since the 1980s would have had little to no meaningful affect on the soil moisture. 10 1.4. References ACIA (2004) Arctic Climate Impact Assessment. Cambridge University Press, Cambridge. Arft A M , Walker MD, Gurevitch J, et al. (1999) Response of Arctic tundra plants to experimental warming: meta-analysis of the International Tundra Experiment. Ecological Monographs, 69(4), 491-511. Billings WD, Peterson K M , Luken JO, Mortensen D A (1984) Interaction of increasing atmospheric carbon dioxide and soil nitrogen on the carbon balance of tundra microcosms. Oecologia, 65, 26-29. Bliss L C , Courtin G M , Pattie DL, Riewe RR, Whitfield DWA, Widden P (1973) Arctic Tundra Ecosystems. Annual Review of Ecology and Systematics, 4, 359-397. Bliss L C (ed) (1977) Truelove Lowland, Devon Island, Canada: A High Arctic Ecosystem. University of Alberta Press, Edmonton. Chapin FS and Shaver GR (1985) Individualistic growth responses of tundra plant species to experimental manipulations in the field. Ecology, 66, 564-576. Chapin FS and Shaver GR (1996) Physiological and growth responses of arctic plants to a field experiment simulating climatic change. Ecology 77, 822-840. Chapin FS, Jefferies RL, Reynolds JF Shaver GR, Svoboda J (1992) Arctic plant physiological ecology in an ecosystem context. In: Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective, (eds Chapin FS, Jefferies RJ, Reynolds JF, Shaver GR, Svoboda J) pp. 441-450. Academic Press, New York. Chapin FS, Shaver GR, Giblin A E , Nakelhoffer KJ, Laundre JA (1995) Responses of Arctic Tundra to experimental and observed changes in Climate. Ecology, 76(3), 694-711. Epstein HE, Calef MP, Walker MD, Chapin FS, Starfields A M (2004) Detecting changes in Arctic tundra plant communities in response to warming over decadal time scales. Global Change Biology, 10, 1325-1334. Gajewski K and Atkinson DA (2003) Climate Change in Northern Canada. Environmental Reviews, 11, 69-102. 11 Henry GHR (1987) Ecology of Sedge Meadow Communities of a Polar Desert Oasis: Alexandra Fiord, Ellesmere Island, Canada. Ph.D. Dissertation, University of Toronto. Henry GHR (ed) (1997) The International Tundra Experiment (ITEX): Short-term Responses of Tundra Plants To Experimental Warming. Global Change Biology, 3, Supplement 1. Henry GHR, Freedman B, Svoboda J (1990) Standing crop and net production of ungrazed sedge meadows of a polar desert oasis. Canadian Journal of Botany, 68, 2660-2667. Hinzman LD, Bettez ND, Bolton WR et al. (2005) Evidence and implications of recent climate change in northern Alaska and other Arctic Regions. Climate Change, 72(3), 251-298. IPCC (2001) Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II, and III to the Third Assessment Report of the Integovernmental Panel on Climate Change (eds. Watson, R.T. and the Core Writing Team). Cambridge University Press, Cambridge, and New York, 398 pp. Johnson L C , Shaver GR, Cades D H Rastetter E, Nadelhoffer K, Giblin A, Laundre J, Stanley A (2000) Plant carbon-nutrient interactions control C O 2 exchange in Alaskan wet sedge tundra ecosystems. Ecology, 81(2), 453-469. Jonasson S, Michelsen A, Schmidt IK (1999a) Coupling of nutrient cycling and carbon dynamics in the Arctic, integration of soil microbial and plant processes. Applied Soil Ecology, 11, 135-146. Jonasson S, Michelsen A, Schmidt IK, Nielsen E V (1999b) Responses in Microbes and Plants to Changed Temperature, Nutrient, and Light Regimes in the Arctic. Ecology, 80(6), 1828-1843. Kaye JP and Hart SC (1997) Competition for nitrogen between plants and soil microorganisms. Trends in Ecology and Evolution, 12, 139-143. Kielland K (1995) Landscape pattern of free amino acids in Arctic tundra soils. Bio geochemistry 31, 85-98. 12 Mack M C , Shuur E A G , Bret-Harte MS, Shaver GR, and Chapin FS (2004) Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization. Nature, 431, 440-443. Maxwell B (1997) Responding to global climate change in Canada's Arctic, Volume II of the Canada Country Study: Climate impacts and adaptation. Environment Canada, 104 pp. Michelutti N, Douglas MSV, Smol JP (2003) Diatom response to recent climatic change in a high arctic lake (Char Lake, Cornwallis Island, Nunavut). Global and Planetary Change, 38, 257-271. Myneni RB, Keeling CD, Tucker CJ, Asrar G, Nemanl RR (1997) Increased plant growth in the northern high latitudes from 1981 to 1991. Nature, 386, 698-702. Nadelhoffer KJ, Giblin A E , Shaver GR, Linkins A E (1992) Microbial processes and plant nutrient availability in Arctic soils. In: Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective, (eds Chapin FS, Jefferies Rj, Reynolds JF, Shaver GR, Svoboda J) pp. 441-450. Academic Press, New York. Oechel WC, Billings WD (1992) Anticipated effects of global change on carbon balance of arctic plants and ecosystems. In: Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective, (eds Chapin FS, Jefferies RJ, Reynolds JF, Shaver GR, Svoboda J) pp. 139-168. Academic Press, New York. Overpeck JT, Hughen K A , Hardy DR et al. (1997) Arctic Environmental Change of the Last Four Centuries. Science 278, 1251-1256. Phoenix GK and Lee JA (2004) Predicting impacts of arctic climate change: past lessons and future challenges. Ecological Research, 19, 65-74. Ritchie JC (1984) Past and Present Vegetation of the Far Northwest of Canada. University of Toronto Press, Toronto. Rolph S (2003) Effects of Experimental Warming on Nitrogen Cycling in the Canadian High Arctic. M.Sc. thesis, University of British Columbia, Vancouver. Schmidt IK, Jonasson S, Michelsen A (1999) Mineralization and microbial immobilization of N and P in arctic soils in relation to season, temperature and nutrient amendment. Applied Soil Ecology, 11, 147-160. 13 Serreze M C , Walsh JE, Chapin FS et al. (2000) Observational evidence of recent change in the northern high latitude environment. Climatic Change, 46, 159-207. Shaver GR, Johnson C, Cades DH, Murray G, Laundre JA, Rastetter EB, Nadelhoffer KJ, Giblin A E (1998) Biomass and C O 2 Flux in Wet sedge tundra: response to nutrients, temperature, and light. Ecological Monographs, 68(1), 15-91. Sturm M , Racine C, Tape K (2002) Increased shrub abundance in the Arctic. Nature, 411, 546-547. Svoboda J and Freedman B (1994) Ecology of a polar desert oasis. Captus University Press, Toronto. van Wijk MT, Clemmensen K E , Shaver GR et al. (2003) Long-term ecosystem level experiments at Toolik Lake, Alaska, and at Abisko, Northern Sweden: generalizations and differences in ecosystem and plant type responses to global change. Global Change Biology. 10, 105-123. Walker MD, Wahren C H , Hollister RD, Henry GHR et al. (2006) Plant community responses to experimental warming across the tundra biome. Proceedings of the National Academy of Sciences USA, 103, 1342-1346. Welker JM, Fahnestock J, Henry GHR et al. (2004) C02 exchange in three Canadian High Arctic ecosystems: response to long-term experimental warming. Global Change Biology, 10, 1981-1995. Wypych S and Bokwa A, 2003. Urban Climate, Jagiellonian University - Cracow / Poland, viewed 22/8/2006 < http://www.atmosphere.mpg.de/enid/3rv.html > . 14 2. RESPONSES OF H I G H A R C T I C S E D G E M E A D O W S T O C L I M A T E W A R M I N G SINCE 19801 2.1. Introduction The global climate is changing rapidly and Arctic regions are showing strong warming responses due to a complex network of feedback processes (Maxwell 1997, Hughen 2000, Sereeze et al. 2000, Polyakov et al. 2002, Michelutti et al. 2003, ACIA 2004). Arctic plants, strongly limited by temperature and soil nutrient availability, respond directly and indirectly to climate change. Indirect effects caused by changes in soil temperature, including changes in active layer depth and nutrient availability, and changes in precipitation affecting soil moisture are usually found to be more important than direct effects of climate on tundra plants (Chapin et al. 1992, Schmidt et al. 1999, Tinker and Ineson 1990, Johnson et al. 2000). Species composition and abundance in Arctic tundra ecosystems have been responsive to historic climate fluctuations, as measured through pollen analysis (Kaakinen and Eronen 2000). Current warming trends are causing dramatic responses measurable over the past 10 to 30 years with remote and direct measurement techniques (Sereeze et al. 2000, Hinzman et al. 2005, Rayback and Henry 2005, Welker et al. 2005). An understanding of the magnitude of changes taking place in the Arctic will enable more accurate prediction of changes expected in the near future. Responses of tundra vegetation to real and simulated climate warming have been studied across a broad range of communities and spatial scales. A common thread found among all such studies is the non-linear nature of tundra species responses to climate change over time (Phoenix and Lee 2004). Time delayed nutrient deficiencies were often cited as the cause of this notable response (Billings et al. 1984, Chapin and Shaver 1985, Oechel and Billings 1992, Chapin et al. 1995, Phoenix and Lee 2004). Fertilization 1 A version of this chapter has been submitted to Global Change Biology as of August 2006. Hill GB and Henry GHR, Responses of High Arctic Sedge Meadows to Climate Warming since 1980. 15 experiments have consistently shown tundra systems to be more responsive to additions of nitrogen and phosphorus than to changes in temperature, light, or C 0 2 (Chapin et al. 1995, Hobbie and Chapin 1998, Shaver et al. 1998, van Wijk et al 2003). If climate warming only influenced tundra species directly through temperature, responses would likely be much smaller than those recorded or experimentally induced. However, elevated temperature has been repeatedly shown to indirectly enhance growth and productivity by enhancing decomposition and mineralization (Chapin et al. 1995, Robinson et al. 1995, Schmidt et al. 2002, Welker et al. 2004, Walker et al. 2006). Increases in productivity, through fertilization or warming, were most pronounced in deciduous dwarf shrubs, including Betula nana (Low Arctic) and Salix arctica (High Arctic), and graminoids, including Carex and Eriophorum spp. (Henry et al. 1986, Chapin et al. 1995, Shaver et al. 1998, Arft et al. 1999, Jones et al. 1999, vanWijk et al. 2003, Walker et al. 2006). Experiments relating increased biomass with warming have been supported by the similar response of control plots to ambient climate warming (Chapin et al. 1995), satellite imagery which showed increases in photosynthesis between 1980 and 1990 through NDVI measures (Myneni et al. 1997), and repeat aerial photography which depicted increasing shrub cover over the last 50 years (Sturm 2001). Despite the relatively large number of temperature and fertilization experiments in tundra systems, most span less than two decades in duration (Chapin et al. 1995, Shaver et al. 1998, Arft et al. 1999, Johnson et al. 2000, vanWijk et al. 2003, Welker et al. 2004, Mack et al. 2004, Walker et al. 2006). Using a dynamic vegetation model, Epstein et al. (2004) predicted that a minimum of two decades are needed before ecosystem response to natural climate change can be effectively measured. Due to notable non linear responses of tundra species with time, many researchers have identified the need for longer-term studies to validate short-term experimental results (Chapin et al. 1995, Arft et al. 1999, Phoenix and Lee 2004; Walker et al. 2006). Additionally, most experiments have been conducted during the summer and in the Low Arctic, primarily in Alaska (Phoenix and Lee 2004) or in northern alpine systems (e.g. vanWijk et al. 2003). 16 Between 1980 and 1984, Henry (1987, Henry et al. 1990) studied sedge meadow ecosystems at Alexandra Fiord (AF), Ellesmere Island, Nunavut (78° 52' N, 75° 47' W), establishing one of Canada's oldest Arctic tundra datasets (Svoboda and Freedman 1994). Warming experiments were established a decade later at A F as part of the International Tundra Experiment (ITEX) (currently chaired by Henry, www.geog.ubc.ca/itex), creating one of the most appropriate sites to study long term tundra responses to ambient climate change. We hypothesized that the climate had warmed over the last two decades at Alexandra Fiord enhancing growth and productivity of sedge meadow species. We assumed that precipitation changes spanning the duration of the study (25 y) had little or no effect on soil moisture in the saturated sedge meadows. It was our objective to compare above and below ground biomass, active layer depth, and soil characteristics between the early 1980s and 2005 seasons. Comparisons were made at both the site scale, to determine the extent of sedge meadow responses, and at the species scale in order to understand responses influencing sedge meadow community structure. 17 2.2. Materials and Methods 2.2.1. Definitions Biomass refers to all live above or below ground plant tissue. Standing crop refers to all green and attached dead vegetation, above or below ground. Litter is unattached above ground dead plant material. 2.2.2. Study Site The lowland at Alexandra Fiord is a glacial sandur (ca. 8 km 2) and is 90% vegetated, 20% of which is dominated by sedge meadows with wet-mesic organic soils (Muc et al. 1989). The lowland is surrounded by steep cliffs (500-700 m a.s.l.) and supplied by snow and glacier melt water throughout the growing season, which is drained by one large river and three smaller streams. Overland flow, through a network of hummocks and hollows, also occurs throughout most sedge meadows at a 1-3% slope. The soils of most sedge meadow communities are saturated throughout the growing season and as a result, associated low decomposition rates have allowed thick litter and organic layers to accumulate. These nutrient deficient cryosols typically have more than 90% of total nitrogen complexed with organic compounds, which limits plant growth and development (Henry 1987, Henry et al. 1986, Rolph 2002). Additional site details can be found in Henry (1987, 1998), Henry et al. (1990), and Svoboda and Freedman (1994). 2.2.3. Climate Analysis Regional mean daily air temperature data were obtained from the Meteorological Service of Canada for Resolute Bay, Cornwallis Island and Eureka, Ellesmere Island between 1970 and 2005. These stations have operated since the early 1950's and are the closest meteorological stations to Alexandra Fiord. Local average daily air temperature at 1.5 m above the ground was measured at two automatic climate stations at Alexandra Fiord, A F Camp (since 1980) and A F Meadow (since 1989). Soil temperature at -10 cm was also measured at the A F Meadow station. Temperature trends were analyzed using linear regressions of: summer (day 90-270), winter (day 271-89), and yearly averages of temperature against time from the beginning of the recording period to 2005. 18 2.2.4. Biomass and Soil Sampling Sedge meadows were analyzed for long-term response to climate change by comparing above and below ground biomass harvests and soil samples taken in 1980-1984 (Henry 1987, Henry et al. 1990) with repeated measurements made at five of the same meadow sites in 2005 (Figure 2.1). Site A was the largest meadow on the lowland (ca. 50 ha), sloped at 1% grade to the coast (north) and had an equal proportion of micro-topographical hummock/hollow cover. Site B was smaller (ca. 3 ha), ca. 600 m south of site A, and had similar site conditions to site A. Site C was located on a plateau, 20-30 m above the lowland, sloped south at 2-3%, and had slightly smaller hummock features. The conditions of sites A, B, and C were similar to those given in Henry (1987). Site D, located on the sandy edge of a small floodplain has experienced multiple flood events in the past 25 years, with one large event in 2001. Site E was on a sandy delta formed by a tributary stream draining into the SW part of the lowland. In the late 1980s overland flow that used to pass through Site E became diverted into channels, which now circumscribe the site. Figure 2.1. Alexandra Fiord, Ellesmere Island; an aerial photo from the southwest, with sites labeled A, B, C, D and E. Distance from Camp to Site E is approximately 2 km. 19 Henry (1987) sampled the sedge meadows with a stratified random design. Above and below ground standing crop was collected from five plots per site per sample period (Henry et al. 1990). In 2005, 30 m transects were established in the same part of the site sampled in the 1980s. Site A was intensively sampled using four transects whereas each of the Sites B, C, D, and E were sampled with only one transect and are referred to as the extensive sites. Each transect began from the first located stake used in Henry's (1987) study and was then extended at a randomly determined bearing. Eight samples were taken from each transect in Site A and six samples were taken from Sites B, C, D, and E. Above ground (AG) standing crop, which included all live green, attached dead, and plant litter above the soil level, was harvested twice during each growing season. The over-winter material was sampled between June 10-20th, immediately following snow melt and surface thaw. Only one transect (with 6 plots) in Site A was used for over-winter sampling. In the 1980's only Sites A & E were sampled for over-winter standing crop. The peak crop was sampled between July 28th-August 3rd, at the estimated maximum standing crop. A G standing crop was harvested within a 20 cm by 50 cm quadrat, using the same methods as Henry (1987). The A G material was sorted by species and then into live green growth (Gr) and attached dead (Att). In order to reduce identification error and increase statistical power, Carex was analyzed as a genus (labeled Carex spp.) with the exception of Carex misandra, which was easily distinguishable. Moss was not included in plot totals due to high uncertainty regarding the above/below ground transition. Samples were dried at 30-40°C for 24-48 hours in the field laboratory and again at 60°C in a drying oven for 24 hours prior to weighing in the lab at UBC (±0.001 g). Below ground biomass was extracted with a ten cm deep by six cm diameter soil corer two to three days after the above ground biomass had been harvested. Two below ground samples were taken from each above ground plot. The samples were washed to remove inorganic sediment, shipped in coolers, and sorted into live and dead roots, live and dead rhizomes, and shrub roots in the lab at UBC. 20 In order to compare soil pH and soil organic carbon between the 1980s and 2005, soil samples were extracted from plots in Site A with the same methodology as belowground biomass. Soil samples were washed and the majority of roots were removed, dried at 50-60 ° C in the field laboratory and again at 60 ° C in a drying oven at UBC, pulverized by hand, and sieved through a two mm screen. Total organic carbon was determined by loss on ignition at 750 ° C for two hours. Soil pH was measured with a glass electrode in a 1:5 soil to distilled water solution. Measurement of soil pH was the only method that may have differed between this study and Henry's (1987) due to an unknown ratio of soil to solution. 2.2.5. Statistics The data from Henry (1987) and the current study were entered using the same format. Species and community data were predominantly non-normally distributed; therefore, all statistical analyses employed were non-parametric. An alpha value of 0.05 was used for all tests. Wilcoxon / Kruskal Wallis tests were used to compare single sites, species, and below ground components between sample years using JMP 4 & 6 for Macintosh. Multi response permutation procedure (MRPP), the non parametric equivalent to M A N O V A , was employed for multiple group means testing, including tests of all sites and species between sample years. McCune and Grace (2002) strongly recommend MRPP over parametric testing procedures when data are not normally distributed and simple sample designs have been utilized. Non Metric Scaling (NMS), also known as multi-dimensional scaling, ordinations were used to visually display and summarize the relationships between plots and sites. McCune and Grace (2002) also strongly recommend NMS ordinations when analyzing plant community data, due to minimal assumptions of sample size and distribution. NMS ordinations were conducted with the 'Thorough Auto-Pilot mode' with preset standards and Sorensen distance (McCune and Grace 2002). Stress values have been included and are used to assess the strength of the structure: values from five to ten are considered good with little real risk of drawing false conclusions, values from 10-20 are acceptable, and values >20 are associated with weakly structured ordinations (McCune and Grace 2002). An in-depth review of NMS 21 and stress values can be found in McCune and Grace (2002). MRPP and NMS analyses were conducted with PC-ORD 4 for PC. 22 2.3. Results and Discussion 2.3.1. Climate Analysis Air temperature records at Resolute and Eureka depict a warming trend in the Canadian High Arctic over the last 30+ years (Figure 2.2). Trends at A F were similar, but winters warmed much more than summers during the 1990s (Figure 2.3). This pattern matches trends predicted by global climate models and observations made at other Eastern Arctic / Northern Atlantic locations (Serreze et al. 2000, ACIA 2004). Both air temperature records at A F correlate strongly (rAFcamP=0.87, rAFmedow=0.93) with the record at Eureka (Table 2.1), which shows warming of 0.8 ° C per decade since 1970 (Figure 2.2). Soil temperature recorded at A F Meadow (Site B) also shows winter warming (p<0.05) to be significantly stronger than summer warming (p>0.05) (Figure 2.4). The winter soil warming trend was likely non linear, given that the slope of the linear regression line (5 ° C per decade) was more than double that of longer term soil warming trends from other coastal Arctic locations (Majorowitz et al. 2004 and Osterkamp 2005). 23 4-1970 1975 1980 1985 1990 1995 2000 2005 Year Figure 2.2. Summer, yearly, and winter average mean daily air temperature from Resolute Bay, Cornwallis Island and Eureka, Ellesmere Island, from 1970 to 2005. Linear regressions represented with dashed lines. Significant linear regression equations (p<0.05) denoted by *. -5 -10 - 1 5 -20 -25 -30 -35 ^ y = 0.051x - 3.9 — — C a m p Summer M | | | [ 1 | u , | — M> y = -0.036x - 2.9 AF Meadow Summer y = 0.13x - 15 Ah Camp Yearly — - -— — • — — *"""" y = 0.051X - 15 — A F Meadow Yearly -40 y = 0.20x - 27 y = 0.13x - 27 AF Camp Winter •AF Meadow Winter 1970 1975 1980 1985 1990 Y e a r 1995 2000 Figure 2.3. Summer, yearly, and winter average mean daily air temperature from Alexandra Fiord Camp and Alexandra Fiord Meadow climate stations, from 1990-2001 and 1990-2003 respectively. Linear regressions represented with dashed lines. Significant linear regression equations (p<0.05) denoted by *. Table 2.1. Correlation matrix (r) of yearly average air temperature from 1991-1999 between climate stations at Resolute Bay, Cornwallis Island, Eureka, Ellesmere Island, A F Camp, Ellesmere Island, and A F Meadow, Ellesmere Island. Correlation Matrix (r) Resolute Eureka AF Camp AF Meadow Resolute 1 Eureka 0.77 1 A F Camp 0.67 0.87 1 A F Meadow 0.67 0.93 0.92 1 26 • Summer Average Temperature •Average Yearly Temperature •Winter Average Temperature 1993 1998 Year 2003 Figure 2.4. Summer, yearly, and winter averaged mean daily soil temperature from Alexandra Fiord Meadow climate station, from 1993-2003. Linear regressions represented with dashed lines. Significant linear regression equations (p<0.05) denoted by *. 2.3.2. Sedge Meadow Response: Site A The above ground over-winter standing crop at Site A was analyzed first, to determine the comparability of the site between sample years; no significant differences were found at the site scale (Figure 2.5). However, we did find peak season standing crop to be significantly greater in 2005 compared with the mean of the 1980, 1981, 1982, and 1983 sample seasons (Figure 2.6). The community in Site A was analyzed at the species scale to determine which species were responsible for the increased overall site green biomass and attached dead. In both Figure 2.7 and Figure 2.8, it can be seen that the response was generally community wide across dominant and minor species. There was no significant variability among the means of the 1980s sample seasons (p>0.05, not shown here) despite variable climate conditions, including significantly different mean peak season surface temperatures and active layer depths (p<0.05) (Henry 1987). Thus, it can be effectively assumed that responses measurable through comparisons of sedge meadow standing crop are relatively insensitive to short term changes in environmental conditions, and one season of sampling in 2005 can accurately represent the short term stable state of sedge meadows at AF. Supporting this inference, five years of temperature enhancement with open top greenhouses did not induce changes in sedge meadow cover at A F (Henry et al. in preparation). 28 a. c u c d w Vi - a c 3 o a (U > c E 450 400 350 300 250 200 150 100 50 • 1980's • 2005 1981 1982 1983 2005 Year Figure 2.5. Site A over-winter above ground standing crop. Data are means with standard error. Significantly different means (p<0.05) between years within site denoted by *. n i 9 8 i , i 9 8 2 . i 9 8 3 A=5, n2 005 A=6. TWO plots in 1983 contained anomoalously large Dryas integrifolia and litter masses. O c U O/J c d a C>0 5ij 300 200 100 1980-1983 Year 2005 Figure 2.6. Site A peak season above ground standing crop. Data are means with standard error bars. Significantly different means (p<0.05), between 1980-1983 and 2005, denoted by *. n 1 9 8o s A=20, n 2 0 0 5 A=30. % 31 c 3: P . ra g H O -; CT cf5' s p ft c a a O 5 s A O b L/l o ? n n a >•< n PL (t a o S & a* * to O o era c o to C-o •g o n 5' BS •J-. 0 3 is c < o H a c a p-cra H n h a 5" ca o N s—* P3 & S O =r n a I n 31 c 0 r f &3 —. C 5 c a Green A b o v e Ground Biomass and Attached Dead (g/m 2) Carex (Gr) Carex (Att) C. misandra (Gr) C. misandra (Att) Eriophorum triste (Gr) Eriophorum triste (Att) Dryas int. (Gr) Dryas int. (Att) 100 Moss Litter Figure 2.9. Site A moss (not included in plot totals) and litter peak season above ground standing crop. Data are means with standard error bars. No significantly different means between years. ni 9 8o s A=20, n2oo5 A=30. In order to account for the discrepancy between the elevated peak standing crop (Figure 2.6) and the stable over-winter standing crop (Figure 2.5), decomposition likely increased, removing senesced leaves and litter from the now more productive above ground meadows. In addition, Figure 2.9 shows that there was no measurable difference in litter masses between years, strengthening the inference that decomposition has increased. However, it is possible that litter weights are not only controlled by decomposition, but also by the spring melt and overland flow which has the potential to remove litter each year. Spring melt was not collected and filtered for litter material. Decomposition comparisons were also not conducted, but increased rates were expected (Phoenix & Lee 2004) and have been shown to occur through wet sedge tundra warming experiments (Welker et al. 2004). Increased decomposition has been shown to lead to elevated mineralization or partial mineralization of organic nitrogen, both of which are useable by Carex species (Chapin et al. 1993, Rolph 2003). The vast majority (>90%) of the biomass in arctic wet sedge communities occurs belowground in roots and rhizomes (Bliss 1977, Henry et al. 1990). We expected increases in below ground standing crop and biomass to occur with climate warming, given the above allocation ratio and the results of wet sedge fertilization experiments (Shaver et al. 1998). Despite observations of high spatial heterogeneity, univariate and multivariate comparisons showed that within Site A, live and dead roots, live rhizomes, and the community as a whole had all significantly increased biomass or standing crop since the early 1980s (p<0.05) (Figure 2.10). 34 1980-1983 2005 a. o i-U oo wo O J Lti 1000 2000 3000 4000 5000 Figure 2.10. Site A below ground standing crop. Data are means with standard error bars. Significantly different means (p<0.05), between 1980-1983 and 2005, denoted by *. ni 9 8 0sA=19, n 2 0 05 A=24. 2.3.3. Sedge Meadow Response: Sites B, C, D, &E Site E contained up to ca. 5 times more over-winter (Figure 2.11) and peak season (Figure 2.12) mean standing crop in 2005 when compared with 1981, largely due to significantly greater masses of live and attached dead Carex spp. (p<0.05) (Figure 2.13) compared to Eriophorum triste or Dryas integrifolia (Figure 2.14) and litter (p<0.05). In 2005 litter contributed 360 ± 77 g m" to the total standing crop while in 1981 it contributed only 53 ± 13 g m~2. This response was likely affected by a changing flood disturbance regime in the late 1980s when glacial melt was diverted, channeling water around Site E instead of flowing through it. The change of flood regime and resulting lowering of the local water table may have initiated slight drying and aeration of the soil, which could have stimulated increases in productivity and standing crop in addition to increases associated with climate warming. This response is supported by Gebauer et al. (1996) who showed a four to eight fold increase in soil nitrogen with increased aeration in the later (drier) half of an arctic growing season in both sedge meadows and tussock tundra. Sites B and C showed no significant difference in mean peak standing crop between sampling periods (Figure 2.12). Small sample sizes may explain this lack of significance as the mean Shannon diversity index, location and soil properties are very similar to Site A (Henry 1987). Site D also showed no significant difference between sample years, although mean standing crop was slightly lower in 2005 than in 1981 (Figure 2.12). Site D was disturbed by multiple flooding events, the most recent in 2001, which covered all above ground vegetation with sediment, likely muting any response to climate warming. 36 600 -t 1981 2005 Figure 2.11. Over-winter above ground standing crop at Site E (Sites B-D in the 1980's were not sampled for over-winter standing crop). Data are means with standard error bars. Significantly different means (p<0.05) between years within site denoted by *. nm E=5, n2005 E=6. Figure 2.12. Site B, C , D, and E peak season above ground standing crop. Data are means with standard error bars. Significantly different means (p<0.05), between 1981 and 2005, denoted by *. ni 9 8 i B,C,D,E=5, n 2 0 0 5 B,C,D,E=6. •S-. s. rt E c s C E O 00 o > o C D Carex spp. (Gr) B C D Carex spp. (Att) Figure 2 .13 Site B , C , D and E mean peak season above ground green biomass ( G ) and attached dead (Att) o f Carex spp and standard error bars. S ign i f i can t ly different means (p<0.05) between years w i t h i n sites and species denoted by *. n 1 9 8 i B,C,D,E=5, n 2 0 05 B,C,D E=6. F i g u r e 2 . 1 4 . S i t e B , C , D a n d E p e a k s e a s o n a b o v e g r o u n d g r e e n b i o m a s s ( G ) a n d a t t a c h e d d e a d ( A t t ) o f Eriophorum triste a n d Dryas integrifolia. D a t a a r e m e a n s w i t h s t a n d a r d e r r o r b a r s . N o s i g n i f i c a n t l y d i f f e r e n t m e a n s b e t w e e n y e a r s w i t h i n s i t e s a n d s p e c i e s d e s p i t e a p p a r e n t l y l a r g e d i f f e r e n c e s i n m e a n s a n d n o n o v e r l a p p i n g e r r o r b a r s . nm\ B,C,D,E=5, n 2oo5 B,C.D,E=6. The majority of common species at Site A showed significantly higher mean peak above ground green biomass or attached standing crop in 2005 than in the early 1980s (Figure 2.7 & Figure 2.8). In sites B, C, D, and E the three dominant genera/species, Carex spp. (Figure 2.13), Eriophorum angustifolium triste, and Dryas integrifolia (Figure 2.14) showed consistently higher, but largely non-significant, biomass and standing crop in 2005 compared with 1981. This positive community wide response of increased biomass and standing crop over time is depicted in NMS ordinations by the shift in positions between sample periods (1980s and 2005) of plots in Site A (Figure 2.15) and those in Sites B-E (Figure 2.16). MRPP test results support distinctive grouping by years in Site A (p<0.01)(Figure 2.15). MRBP (blocked) tests could not be used to test extensive site yearly grouping (Figure 2.16) as multiple measures within blocks were not permitted in PC-ORD 4. Species that were significantly different in biomass between sampling periods in Site A (Figure 2.7 & Figure 2.8) and Sites B-E (Figure 2.13 & Figure 2.14) were highly correlated with the axes of the NMS ordinations, which resulted in low (adequate) stress values (Figure 2.15 & Figure 2.16). 41 to • 4^  • • • • 4 • • • • * • • • • * • •» • * • • • » 1980s • * 2005 • A x i s 1 Figure 2.15. NMS of all plots in Site A. Axes 1, 2 and 3 significant (p<0.02). Final Stress = 14. Strong axis 1 correlations (r>0.6): E. triste. (Gr, Att), D. integrifolia. (Gr, Att). Strong axis 2 correlations (r>0.5): Carex spp. (G,Att), E. triste (G, Att), Dryas int. (G, Att). Litter square root transformed to remove dominance on axis. Significant MRPP grouping by years (p<0.001). AXK2 1 Axis 2 Figure 2.16A) NMS of all plots harvested for above ground standing crop in Sites B , C, D, E. Final stress-10.1. B ) . Site means plotted from NMS plot coordinates in A) with standard error bars on both axes. Directional response arrows denote site shifts in multivariate space between 1981 and 2005. Strong axis 2 correlations (r>0.4): D. integrifolia (Att), litter. Strong axis 3 correlations (r=0.5): Carex spp. (Att), D. integrifolia (Att), litter. Shaver et al. (1998) studied warming and fertilization of wet sedge tundra for 6-9 years at Toolik Lake, Alaska, where ecosystem productivity, dominated by graminoids, including Carex spp. and Eriophorum spp., responded positively and significantly to fertilization. Carex cordorhizza was found to be the most responsive to nutrient additions (Shaver et al. 1998), much like the response of Carex membranacea and Carex aquatilis stans, the two dominant graminoids in sedge meadows at A F (Henry et al. 1986). However, species diversity was not dramatically altered at Toolik Lake (Shaver et al. 1998), nor at A F (Shannon diversity values at site A ± SE: Hi9 8 0 s=1.90 ± 0.06, H 2 0 o5=L98± 0.03) due to less dramatic but consistent community wide response. Sedge meadow community diversity in both the Eastern High Arctic and Western Low Arctic appears less responsive to warming than responses in community productivity. 2.3.4. Soil Responses Soil organic carbon, permafrost depths, and soil pH were analyzed for differences in sample year means, but only pH was significantly different. However, yearly means differed by a pH of 0.2; the pH in 1982 was 6.3, and in 2005 was 6.1. This small difference is unlikely to be ecologically meaningful but may be worthy of note for subsequent studies at this site (H. Schrier, pers. comm., 2005). 2.3.5. Sedge Meadow Response to Winter Warming A cause and effect relationship between air/soil warming and elevated sedge meadow productivity cannot be generated without experimental manipulation and controls. Because there are no available controls for ambient climate change on Earth, reliance must be placed upon inference, elimination, and comparisons with other experimental findings. Irrespective of season, multi-factor manipulation experiments show that the influence of temperature is minor in comparison with nutrient additions (Chapin et al. 1995, Phoenix & Lee 2004, van Wijk et al. 2003). Warming at A F was greatest in the winter and sedge meadows likely responded indirectly to elevated winter temperatures through a suite of factors leading to enhanced nutrient availability including lengthened growing seasons, increased decomposition and mineralization rates and/or duration, and 44 enhanced nutrient pools (Rolph 2003). In order to better understand the mechanisms behind tundra response to High Arctic climate warming, field experiments need to focus on winter perturbations where warming has been observed and is predicted to continue (Phoenix & Lee 2004). 2.3.6. Biomass / Carbon Dynamics Carbon fluxes were not measured as part of this study and the long term natural changes remain unknown. However, nine years of experimental warming on ecosystem C 0 2 exchange at Site A showed stronger stimulation of ecosystem respiration than photosynthesis, and much of the increased respiration was likely due to greater decomposition rates (Welker et al. 2004). The results from Welker et al. (2004) are similar to longer studies in Alaska where deep soil organic material was found preferentially decomposed in comparison with near surface or litter material leading to a net loss of carbon (2000 g m" over 20 years) from the tundra ecosystem (Mack et al. 2004). Elevated above ground productivity at A F appears to have been balanced by elevated litter decomposition rates, given that over-winter and litter standing crops were not significantly different between the sample periods. However, the strong increase in below ground standing crop (Figure 2.10), especially dead roots (3706 ± 663 g m" in 2005 and 826 ± 140 g m"2 in the 1980s), indicates that decomposition rates in the soil have not increased in step with root production. Despite supervision by Dr. Henry, the potential for human bias and error during below ground biomass sorting was greater than bias and errors introduced during above ground biomass sorting. Sedge meadows at Site A were experimentally warmed with open top greenhouses as part of the ITEX network. Over a five year period, warming showed no significant changes in plant cover in any meadow functional group, including graminoids (Henry in prep., Walker et al. 2006). However, the long-term (25 y) nature of our ambient change study clearly showed increased productivity at the site and species scale, contributing information that could not be obtained nor induced from short-term experimentation. These results should stimulate the search for sites and data sets that can be revisited and 45 resampled, such as those established during the International Biological Program in the early 1970s (Bliss 1977, Michelutti etal. 2003). The secondary objective was to enable statistical comparisons between 2005 and future study years. Point frame data was collected from peak above ground biomass plots prior to harvest in order to simplify future comparisons. The point frame method and correlations with biomass are reported in the appendix. 46 2.4. References ACIA (2004) Arctic Climate Impact Assessment. Cambridge University Press, Cambridge. Arft A M , Walker MD, Gurevitch J et al. (1999) Response of arctic tundra plants to experimental warming: meta-analysis of the International Tundra Experiment. Ecological Monographs, 69, 491 -511. Billings WD, Peterson K M , Luken JO, Mortensen DA (1984) Interaction of increasing atmospheric carbon dioxide and soil nitrogen on the carbon balance of tundra microcosms. Oecologia, 65, 26-29. Bliss L C (ed) (1977) Truelove Lowland, Devon Island, Canada: A High Arctic Ecosystem. University of Alberta Press, Edmonton. Chapin FS and Shaver GR (1985) Individualistic growth responses of tundra plant species to experimental manipulations in the field. Ecology, 66, 564-576. Chapin FS, Jefferies RL, Reynolds JF Shaver GR, Svoboda J (1992) Arctic plant physiological ecology in an ecosystem context. In: Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective, (eds Chapin FS, Jefferies RJ, Reynolds JF, Shaver GR, Svoboda J) pp. 441-450. Academic Press, New York. Chapin FS, Moilanen L, Kielland K (1993) Preferential use of organic nitrogen for growth by a non-mycorrhizal arctic sedge. Nature, 361, 150-153. Chapin FS, Shaver GR, Giblin A E , Nakelhoffer KJ, Laundre JA (1995) Responses of Arctic Tundra to experimental and observed changes in Climate. Ecology, 76(3), 694-711. Gebauer RLE, Tenhunen JD, and Reynolds JF (1996). Soil aeration in relation to soil physical properties, nitrogen availability, and root characteristics within an arctic watershed. Plant and Soil, 178(1), 37-48. Epstein HE, Calef MP, Walker MD, Chapin FS, Starfields A M (2004) Detecting changes in Arctic tundra plant communities in response to warming over decadal time scales. Global Change Biology, 10, 1325-1334. 47 Henry GHR (1987) Ecology of Sedge Meadow Communities of a Polar Desert Oasis: Alexandra Fiord, Ellesmere Island, Canada. Ph.D. Dissertation, University of Toronto. Henry GHR (ed) (1997) The International Tundra Experiment (ITEX): Short-term Responses of Tundra Plants To Experimental Warming. Global Change Biology, 3, Supplement 1. Henry GHR (1998) Environmental influences on the structure of sedge meadows in the Canadian High Arctic. Plant Ecology, 134, 119-129. Henry GHR, Freedman B, Svoboda J (1986) Effects of fertilization on three tundra plant communities of a polar desert oasis. Canadian Journal of Botany, 64, 2502-2507. Henry GHR, Freedman B, Svoboda J (1990) Standing crop and net production of ungrazed sedge meadows of a polar desert oasis. Canadian Journal of Botany, 68, 2660-2667. Hinzman LD, Bettez ND, Bolton WR et al. (2005) Evidence and implications of recent climate change in northern Alaska and other Arctic Regions. Climate Change, 72(3), 251-298. Hobbie S and Chapin FS (1998) The response of tundra plant biomass, aboveground production, nitrogen and flux to experimental warming. Ecology, 79(5), 1526-1544. Hughen K A , Overpeck JT, Anderson RF (2000) Recent warming in a 500yr old Palaeotemperature record from varved Sediments, Upper Soper Lake, Baffin Is. The Holocene. 10,1, 9-19. Jones M H , Fahnestock JT, Welker JM (1999) Early and Late Winter C02 Efflux from Arctic Tundra in the Kuparuk River Watershed, Alaska, U.S.A. Arctic and Alpine Research, 31, 187-19 Johnson L C , Shaver GR, Cades D H Rastetter E, Nadelhoffer K, Giblin A, Laundre J, Stanley A (2000) Plant carbon-nutrient interactions control C 0 2 exchange in Alaskan wet sedge tundra ecosystems. Ecology, 81(2), 453-469. Kaakinen A and Eronen M (2000) Holocene pollen stratigraphy indicating climatic and tree-line changes derived from a peat section at Ortino, in the Pechora lowland, northern Russia. The Holocene, 10(5), pp 611-620. 48 Mack MC, Shuur E A G , Bret-Harte MS, Shaver GR, and Chapin FS (2004) Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization. Nature, 431, 440-443. Majorowitz JA, Skinner WR, Safanda J (2004) Large ground warming in the Canadian Arctic inferred from inversions of temperature logs. Earth and Planetary Science Letters, 221, 15-25. Maxwell B (1997) Responding to global climate change in Canada's Arctic, Volume II of the Canada Country Study: Climate impacts and adaptation. Environment Canada, 104 pp. McCune B. and Grace JB (2002) Analysis of ecological communities. MjM Software, Glenedon Beach, Oregon, 302 pp. Michelutti N, Douglas MSV, Smol JP (2003) Diatom response to recent climatic change in a high arctic lake (Char Lake, Cornwallis Island, Nunavut). Global and Planetary Change, 38, 257-271. Muc M , Freedman B, Svoboda J (1989) Plant communities of a polar oasis at Alexandra Fiord (79° N), Ellesmere Island. Canadian Journal of Botany, 67, 1126-1136. Myneni RB, Keeling CD, Tucker CJ, Asrar G, Nemanl RR (1997) Increased plant growth in the northern high latitudes from 1981 to 1991. Nature, 386, 698-702. Oechel WC and Billings WD (1992) Anticipated effects of global change on carbon balance of arctic plants and ecosystems. In: Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective, (eds Chapin FS, Jefferies RJ, Reynolds JF, Shaver GR, Svoboda J) pp. 139-168. Academic Press, New York. Osterkamp T E (2005) The recent warming of permafrost in Alaska. Global and Planetary Change, 49, 187-202 Phoenix G K and Lee JA (2004) Predicting impacts of arctic climate change: past lessons and future challenges. Ecological Research, 19, 65-74. Polyakov I, Akasofau I, Bhatt U et al. (2002) Trends and variations in the Arctic climate system. EOS, Transactions of the American Geophysical Union, 83, 457-458. Rayback SA, Henry GHR (2005) A A A R paper in press. Ritchie JC (1984) Past and Present Vegetation of the Far Northwest of Canada. University of Toronto Press, Toronto. 49 Robinson C H , Wookey PA, Parsons AN, Potter JA, Callaghan TV, Lee JA, Press M C , Welker JM (1995) Responses of plant litter decomposition and nitrogen mineralization to simulated environmental change in a high arctic polar semi-desert and a sub arctic dwarf shrub heath. Oikos, 74 (3), 503-512. Rolph S (2003) Effects of Experimental Warming on Nitrogen Cycling in the Canadian High Arctic. M.Sc. thesis, University of British Columbia, Vancouver. Schmidt IK, Jonasson S, Michelsen A (1999) Mineralization and microbial immobilization of N and P in arctic soils in relation to season, temperature and nutrient amendment. Applied Soil Ecology, 11, 147-160. Schmidt IK, Jonasson S, Shaver GR, Michelsen A, Nordin A. (2002) Mineralization and distribution of nutrients in plants and microbes in four arctic ecosystems: responses to warming. Plant and Soil, 242, 93-106. Serreze M C , Walsh JE, Chapin FS et al. (2000) Observational evidence of recent change in the northern high latitude environment. Climatic Change, 46, 159-207. Shaver GR, Johnson C, Cades DH, Murray G, Laundre JA, Rastetter EB, Nadelhoffer KJ, Giblin A E (1998) Biomass and CO2 Flux in Wet sedge tundra: response to nutrients, temperature, and light. Ecological Monographs, 68(1), 75-97. Sturm M , Racine C, Tape K (2002) Increased shrub abundance in the Arctic. Nature, 411, 546-547. Svoboda J and Freedman B (1994) Ecology of a polar desert oasis. Captus University Press, Toronto. Tinker PB and Ineson P (1990) Soil Organic matter and Biology in relation to climate change. In: Soils on a Warmer Earth (eds Scharpenseel H.W. and Schomaker M . and Ayoub A) pp. 71-87, Nairobi, van Wijk MT, Clemmensen K E , Shaver GR et al. (2003) Long-term ecosystem level experiments at Toolik Lake, Alaska, and at Abisko, Northern Sweden: generalizations and differences in ecosystem and plant type responses to global change. Global Change Biology. 10, 105-123. Walker MD, Wahren CH, Hollister RD, Henry GHR et al. (2006) Plant community responses to experimental warming across the tundra biome. Proceedings of the National Academy of Sciences USA, 103, 1342-1346. 50 Welker JM, Fahnestock J, Henry GHR et al. (2004) C02 exchange in three Canadian High Arctic ecosystems: response to long-term experimental warming. Global Change Biology, 10, 1981-1995. Welker JM, Rayback SA and Henry GHR (2005) Arctic and North Atlantic Oscillation phase changes are recorded in the isotopes (dl80 and dl3C) of Cassiope tetragona plants. Global Change Biology, 11: 991'-1002. 51 3. Synthesis The primary objective of this study was to make comparisons between samples measured in the early 1980s and again in 2005. All valid comparisons were included in Chapter 2. The secondary objective was to ensure this study provided a solid foundation upon which future comparisons could be made. This chapter outlines steps taken during the 2005 sample season to ensure this secondary object was met, and provides a synthesis of the results. 3.1 Synthesis In the 15 years the climate at Alexandra Fiord, Ellesmere Island, has warmed, as shown through increasing yearly and winter averages of mean temperature. These records correlate strongly with regional records of longer duration at Eureka, Ellesmere Island, and Resolute Bay, Cornwallis Island, all of which are supported by general trends and predictions published in reviews of Arctic climate change (Serreze et al. 2000, ACIA 2004, Hinzman et al. 2005). I hypothesize that since the early 1980s air and, more importantly, soil warming stimulated the decomposition of organic carbon enhancing soil nutrients which elevated the productivity and standing crop of wet sedge meadows at Alexandra Fiord. Overall, both aboveground and belowground biomass had increased over the 25 year period. This increase can likely be attributed to the warming climate since the 1980s as annual variation in net primary production was found to be insignificant over the period 1980-1984, despite large differences in annual climate. Dominant genera from each growth form showed significant positive response with increases in above and below ground biomass. Our study is, to our knowledge, the first to show responses in high arctic terrestrial systems to ambient climate change over the past twenty-five years. 52 3.2. Future Research Plant cover estimates were sampled in both time periods, but due to incomparable techniques, comparisons using species cover data were not made. Visual estimation of cover was commonly used in the 1980s, but due to large inconsistencies between researchers, more standardized estimates have been adopted. We utilized point frame quadrats, due to their higher degree of objectivity (Barbour Burke and Pitts 1987, Walker 1996, Bean and Henry 2003) on all above ground plots in all sites one week prior to peak season harvests in the 2005 season. We used 50 cm x 50 cm quadrats, which were partitioned into 100 points at five cm intervals on both axes. The point frame was positioned identically over each harvest plot and 40 points were taken within the 20cm by 50cm harvest quadrat. The objective of this sampling was to create a baseline data set of cover estimates. In the future, these quadrats could be sampled as repeat measurements over time to produce a time series of community cover change with much less effort than repeating biomass harvests. A complete repeat of the 2005 point frame sampling across all sites and transects would take approximately two weeks, including training, sampling, and data entry. A complete resampling of the 2005 peak biomass harvest across all sites and transects, including sorting, drying, weighing, and data entry would take six to eight weeks. In order to validate the cover estimates, each species cover estimate was correlated with biomass / standing crop values in all plots sampled with both techniques (Table 3.1). Species correlations were similar to those found in ITEX permanent plots at Site A and in other communities in the AF lowland (Henry unpublished). Common species score higher correlations than rare species due to the limited number of point in a plot (40) and the dense network of species in sedge meadow hummocks. Shrubs score high correlations due to their horizontal spreading growth form which is more likely to intercept a vertical point than is the leaf of a sedge due to is vertical growth form. Negative correlations show the limited use of point frame / biomass correlations for rare species. 53 To enable statistical comparisons in future years, summary data tables of over-winter above ground biomass (Table 3.2) peak above ground biomass (Table 3.3) below ground biomass (Table 3.4), and soil pH (Table 3.5) have been included. Transect stake locations were recorded with GPS, and left in situ to facilitate the relocation of quadrat frames for cover and biomass comparisons in the future (Appendix). 54 3.2. Tables Table 3.1. Point frame hits correlated (r) with biomass / standing crop mass from all plots sampled with both techniques Species r Carex spp. (Gr) 0.33 Carex spp. (Att) 0.58 C. stans (Gr) 0.75 C. Stans (Att) 0.86 C. mem (Gr) 0.41 C. mem (Att) 0.73 C. misandra (Gr) 0.56 C. misandra (Att) 0.09 C. capilaris (Gr) 0.43 C. capilaris (Att) 0.45 is. /rate (Gr) 0.49 E. triste (Att) 0.40 Kobresia spp. (Gr) 0.71 Kobresia spp. (Att) 0.44 Arctagrostis lat. (Gr) 0.80 Arctagrostis lat. (Att) -0.07 Juncus spp. (Gr) -0.09 Juncus spp. (Att) -0.10 Polygonum viviparum (Gr) 0.51 Polygonum viviparum (Att) 0.23 Equisetum spp. (Gr) 0.98 Saxifraga spp. (Gr) 0.48 Saxifraga spp. (Att) 0.82 Z). integrifolia (Gr) 0.79 D. integrifolia (Att) 0.78 Sa/z'x arctica (Gr) 0.90 SaZ/x arctica (Att) 0.52 Moss 0.50 Total PF Hits / Total Biomass 0.54 55 Table 3.2. Mean over-winter biomass and standing crop (, ri2005E=6. _2 g m" ) of species/] 'groups ± standard error. n80'sA=15, n2oo5A=6, n8iE=5, Species 1980s Site A 2005 Site A 1981 Site E 2005 Site E Carex spp. (Gr) 5.04 ± 0.67 9.07 ± 1 . 1 6 2.89 ± 0 . 2 5 12.28 ± 2 . 1 9 Carex spp. (Att) 34.96 ± 4.7 49.18 ± 7 . 1 7 50.42 ± 10.13 96.62 ± 15.87 E. triste. (Gr) 5.79 ±1.17 4.33 ± 1 . 9 2 0.05 ± 0.03 0.38 ± 0 . 1 6 E. triste. (Att) 34.08 ± 6.92 24.46 + 11.84 0.34 ± 0 . 3 2.27 ± 1.01 Kobresia spp (Gr) 0.11 ± 0 . 0 7 0.37 ± 0 . 1 7 0.00 ± 0 0.01 ± 0 Kobresia spp. (Att) 0.68 ± 0 . 3 6 4.69 ± 2 . 1 1 0.00 ± 0 0.13 ± 0 . 0 7 A. latifolia. (Gr) 0.00 ± 0 0.00 ± 0 0.08 ± 0.07 0.03 ± 0.03 A., latifolia (Att) 0.03 ± 0.02 0.00 ± 0 0.19 ± 0 . 1 4 0 . 1 8 ± 0 . 1 8 Juncus spp. (Gr) 0.09 ± 0.06 0.02 ± 0.02 0.00 ± 0 0.00 ± 0 Juncus spp. (Att) 0.01 ± 0 . 0 1 0 . 1 7 ± 0 . 1 2 0.00 ± 0 0.00 ± 0 P.viviiparum. (Gr) 0.00 ± 0 0.07 ± 0.05 0.00 ± 0 0.02 ± 0.02 P. viviparum. (Att) 0.00 ± 0 0.66 ± 0.57 0.00 ± 0 0.09 ± 0.09 Pedicularis spp. (Gr) 0.00 ± 0 0.02 ± 0.02 0.00 ± 0 0.01 ± 0 . 0 1 Pedicularis spp. (Att) 0.00 ± 0 0.09 ± 0.09 0.00 ± 0 0 . 1 9 ± 0 . 1 7 Equisetum spp. (Gr) 0.34 ±.22 0.83 ± 0 . 7 3 0.00 ± 0 0.00 ± 0 Saxifraga spp. (Gr) 0.13 ±.08 0.00 ± 0 0.00 ± 0 0.00 ± 0 Saxifraga spp. (Att) 1.18 + 78 0.00 ± 0 0.00 ± 0 0.00 ± 0 Z). integrifolia (Gr) 13.62 ± 4 . 7 4 1.22 ± 0 . 6 6 0.23 ± 0 . 1 9 0.00 ± 0 D. integrifolia (Att) 28.20 ± 9.66 45.73 ± 17.39 0.95 ± 0 . 8 6 0.00 ± 0 Salix arctica. (Gr) 0.85 ±.39 0.04 ±0.030 5.33 ± 1.92 0.56 ± 0 . 4 1 Safe arctica. (Att) 0.47 + 32 1.11 ± 0 . 4 8 0.34 ± 0 . 3 4 13.15 ± 8 . 8 9 Litter 110.63 ±18.03 81.72 ±13.99 60.53 ± 28.34 367.98 ± 27.39 Table 3.3. Mean peak above ground biomass and attached dead (g/m2) of all species or groups ± standard error, niggos A=20, n2oo5 A=30, n)98i B,C,D,E=5, n2005 B,C,D,E=6. 1980s Site 2005 Site 1981 Site 2005 Site 1981 Site 2005 Site 1981 Site 2005 Site 1981 Site 2005 Site Species A A B B C C D D E E 10.4± 23.7± 9.8± 44.3± 11.3± 24.0+ 13.8± 25.5± 18.0+ 43.5± Carex (Gr) 1.9 1.7 4.3 7.8 2.4 6.1 3.7 4.4 5.8 4.3 15.01 34.4± 32.6± 67.0+ 30.5± 63.2± 37.3± 32.3± 23.5± 109.0+ Carex (Att) 2.4 4.3 15.2 9.0 8.4 21.7 10.0 5.6 6.4 9.5 C. misandra 1.1± 2.2+ 2.4± 0.6± 1.3± 0.2± (GT) 0.3 0.3 1.1 0.0±0 0.4 0.5 0.2 0.0±0 0.0±0 0.0±0 C. misandra 4.3± 14.3± 16.8± 3.2± 9.1± 0.4± (Att) 1.3 2.2 9.5 0.0±0 1.9 2.5 0.4 0.0±0 0.0+0 0.0+0 13.7± 17.1± 8.0± 11.2± 4.3± 15.1± 1.6± 14.5± 0.4± 1.1± E. triste. (Gr) 1.8 1.1 2.2 2.9 1.4 5.1 1.2 3.7 0.3 0.4 23.5± 31.5± 18.9+ 16.6± 7.3± 41.1+ 4.3± 15.1± 0.3± 4.0± E. triste (Att) 3.5 3.3 6.3 4.2 1.4 15.6 3.8 2.6 0.2 1.4 Kobresia spp. 0.9± 0.4± 0.4± 0.0± 0.7± 0.0± (Or) 0.5 0.1 0.2 0.0±0 0.0 0.3 0.0±0 0.0±0 0.0±0 0.0 Kobresia spp. 1.3± 1.7± 1.7± 0.1± 3.1± 0.1± (Att; 0.7 0.5 0.7 0.0±0 0.1 1.5 0.0±0 0.0±0 0.0±0 0.1 A. latifolia 0.7± 0.6+ 1.0± 0.4± 0.6± 1.7± 1.1± 1.8± 0.5± 0.5± (Gr) 0.6 0.2 0.5 0.4 0.4 1.7 1.1 1.3 0.5 0.2 A. latifolia 0.1 + 0.5± 1.5± 0.4± 0.3± 1.2± 0.3± 0.8± 0.1± 0.7± (Att) 0.1 0.3 1.0 0.3 0.2 1.0 0.3 0.5 0.1 0.2 Juncus spp. 0.1± 0.4± 0.0± 0.1± 5.9+ 0.1± 0.0± 0.0± 0.0± (Gr) 0.0 0.1 0.0 0.0 0.7 0.1 0.0 0.0 0.0 0.0±0 Juncus spp. 0.5± 0.1± 0.1± 60.6± 0.1± 0.0+ 0.0± (Att) 0.1 + 0 0.1 0.1 0.1 2.0 0.1 0.0 0.0 0.0±0 0.0±0 P. viviparum. 0.2± 0.4± 0.6± 1.2± 0.1± 0.6± 0.1± 2.4± 0.1 + (GT) 0.1 0.1 0.3 0.3 0.1 0.1 0.1 1.1 0.0+0 0.1 P. viviparum. 0.0± 0.3± 0.7± 0.0± 0.6± 1.8± 0.1± (Att) 0.0 0.1 0.0±0 0.3 0 0.2 o.o+o 0.9 0.0±0 0.1 Previous table continued Equisetum 0.6± 0.4± 0.0+ 0.1+ 0.1+ 0.1+ 8.1+ spp. (Gr) 0.2 0.3 0.4±0.3 0.0 0.1 0.1 0.8 1.6 0.0+0 0.0+0 Saxifraga 0.0± 0.1± spp. (Gr) 0.0 0.0 0.0+0 0.0+0 0.0+0 0.0+0 0.0+0 0.0+0 0.0+0 0.0+0 Saxifraga 0.1+ 0.1± spp. (Att) 0.1 0.1 0.0+0 0.0±0 0.0+0 0.0+0 0.0+0 0.0+0 0.0+0 0.0+0 Dryas int. 4 .6± 7.0± 2.3+ 6.3+ . 2.3+ 8.2+ 5.3+ 14.3+ 0.9+ 0.0+ (Gr) 1.3 1.8 1.3 3.7 1.1 3.5 3.4 4.4 0.4 0.0 Dryas int. 22.9+ 43 .1± 22.7+ 15.9± 31.3+ 50.0± 55.9+ 25.5+ 1.1+ 0.1+ (Att) 6.6 9.8 13.0 9.2 17.5 20.3 39.2 8.9 0.5 0.1 Salix arctica 0.5± 7.2+ 0.0+ 0.9+ 6.1+ 17.5± 1.8+ 5.3+ (Gr) 0.3 0.3+0.1 0.0+0 3.6 0.0 0.8 1.7' 5.0 0.9 1.5 Salix arctica 0.4± 5.2+ 1.2+ 1.5+ 31.2+ 27.2+ 5.5+ 21.7+ (Att) 0.3 0.4+0.2 0.0+0 1.9 0.7 1,5 12.4 8.1 1.7 6.9 92 .6± 146.2+ 76.2± 103.1+ 97.1+ 160.6+ 49.7+ 53 .4± 360.0+ Litter 15.7 92.4±10.7 39.6 27.9 23.9 26.7 41.2 15.8 12.7 76.6 oo Table 3.4. Site A means of below ground biomass / standing crop components ± standard errors (g/m2). n8o'S=19. n2oo5=24. Category 1980s 2005 Live roots 328.5 ± 4 9 . 5 549.5 ± 7 8 . 2 Dead roots 826.2 ± 139.9 3706.2 ± 6 6 3 . 5 Live rhizomes 52.3 ± 8.2 124.5 ± 19.6 Dead rhizomes 89.5 ± 22.4 66.1 ± 11.8 Shrub roots 75.1 ± 2 2 . 3 56.2 ± 2 1 . 4 Total 1371.6 ± 177.0 4502.4 ± 6 7 3 . 0 Table 3.5. Soil pH ± standard errors. Differing soil/solution ratios were used in each sample year. Comparisons between sample years may not be valid. See Chapter 2 for details. 1982 2005 Soil pH 6.31 ± 0 . 0 7 6.10 ±0 .05 59 3.3. References ACIA (2004) Arctic Climate Impact Assessment. Cambridge University Press, Cambridge. Barbour M G , Burke JH, and Pitts WD (1987) Terrestrial Plant Ecology. The Benjamin/ Cummings Publishing Company, Inc., California. Bean D, Henry GHR (2003) CANTTEX Field Manual Part A: Setting Up a Basic Monitoring Site. EMAN-North, Environment Canada - www.emannorth.ca/canttex. Hinzman LD, Bettez ND, Bolton WR et al. (2005) Evidence and implications of recent climate change in northern Alaska and other Arctic Regions. Climate Change, 72(3), 251-298. Serreze M C , Walsh JE, Chapin FS et al. (2000) Observational evidence of recent change in the northern high latitude environment. Climatic Change, 46, 159-207. Walker M (1996) Community baseline measurements for ITEX studies. In: ITEX Manual (eds Molau U, M0lgaard P), Danish Polar Centre, Copenhagen. 60 4. A P P E N D I X 4.1. Plot Dimensions The most common plot sizes used for tundra biomass harvests, most of which are conducted at the LTER near Toolik Lake and near Abisco, Sweden, are 20cm by 20cm (van Wijk et al. 2003). However, in order to avoid matching the scale of plots to the scale of the hummock / hollow micro-topography at Alexandra Fiord, we used 20cm by 50cm plots (Henry 1987). It was our intention to capture within each plot both hummock and hollow community components. 4.2. Additional Data Additional data included here may be useful if Sites A, B, C, D, E are resampled at a future date. A l l O denotes Site A, transect 1, plot 1, over-winter harvest. A l IP denotes Site A, transect 1, plot 1, peak harvest. Plots located adjacent to the center plot in a transect which were strongly correlated with that center plot were removed in order to ensure independent samples. 61 Table 4.1a. Total point frame hits within a 50 cm by 50 cm frame with 5 cm intervals (40 points/frame). Species A 1 1 P A 1 2 P A 1 3 P A 1 4 P A 1 5 P A 1 6 P A 1 8 P A 2 1 P A 2 2 P A 2 3 P A 2 4 P A 2 5 P A 2 6 P A 2 7 P A 2 8 P A 2 9 P A 3 1 P Carex spp. (Gr) 9 18 19 35 25 31 15 16 11 10 14 10 6 21 30 19 19 Carex spp. (Att) 4 30 25 10 33 4 25 40 22 35 18 26 15 35 26 27 33 C. stans (Gr) 2 8 9 3 17 14 7 1 0 1 8 1 0 2 0 0 5 C. stans (Att) 2 22 21 4 21 1 21 1 0 1 6 1 0 0 1 0 3 C. membranacea (Gr) 4 9 9 32 4 17 8 10 11 8 0 6 6 17 28 19 10 C. membranacea{Att) 0 8 4 6 8 3 3 38 20 34 12 22 15 34 24 27 26 C. misandra (Gr) 1 1 0 0 2 0 0 5 0 1 6 2 0 1 2 0 2 C. misandra (Att) 1 0 0 0 3 0 0 1 2 0 0 2 0 1 1 0 3 C. capilaris (Gr) 2 0 1 0 2 0 0 0 0 0 0 1 0 1 0 0 2 C. capilaris (Att) 1 0 0 0 1 0 1 0 0 0 0 1 0 0 0 0 1 E triste (Gr) 24 8 7 13 9 20 21 18 16 19 11 12 19 23 17 26 9 E. triste (Att) 31 9 4 2 4 11 18 30 23 23 19 11 25 23 14 24 15 Kobresia spp. (Gr) 0 0 0 0 2 3 1 0 0 0 0 2 2 0 0 0 0 Kobresia spp. (Att) 0 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0 0 A. latifolia. (Gr) 1 0 0 0 0 0 0 0 0 3 0 0 0 6 1 2 0 A. latifolia (Att) 0 0 0 0 0 5 0 0 0 0 3 0 0 0 0 0 1 Juncus spp. (Gr) 0 0 0 0 2 0 2 0 0 0 0 1 0 0 1 0 0 Juncus spp. (Att) 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /*. viviparum (Gr) 0 0 0 0 0 0 2 0 0 1 1 0 1 0 0 0 0 P. viviparum (Att) 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 1 Equisetum spp. (Gr) 0 • 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Saxifraga spp. (Gr) 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Saxifraga spp. (Att) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D. integrifolia (Gr) 3 5 1 6 2 4 4 5 1 4 2 11 7 6 5 3 2 D integrifolia (Att) 1 2 0 0 1 2 6 10 2 4 1 18 10 6 4 0 1 Salix arctica (Gr) 2 1 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 Safe arctica (Att) 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 Moss 10 16 4 2 6 0 6 10 0 3 8 7 3 0 2 5 5 Table 4.1b. Total point frame hits within a 50cm by 50cm frame with 5cm intervals (40 points/frame). Species A 3 2 P A 3 3 P A 3 4 P A 3 5 P A 3 6 P A 3 7 P A 3 8 P A 3 9 P A 4 1 P A 4 2 P A 4 3 P A 4 4 P A 4 5 P A 4 6 P A 4 7 P A 4 8 P A 4 9 P Carex spp. (Gr) 15 14 15 11 2 10 17 12 26 19 12 10 22 21 11 11 11 Carex spp. (Att) 15 20 25 21 13 21 22 16 42 44 21 24 30 36 18 18 13 C. stans (Gr) 7 2 2 0 0 1 0 2 0 2 0 0 2 5 0 0 0 C. stans (Att) 0 4 0 0 0 2 0 1 0 4 0 0 0 1 0 0 0 C. membranacea (Gr) 8 5 11 9 2 6 17 6 25 11 12 9 14 14 9 9 9 C. membranacea(Att) 15 7 25 20 13 14 22 11 41 37 21 22 21 32 15 9 10 C. misandra (Gr) 0 0 0 1 0 3 0 2 1 6 0 1 4 1 1 1 2 C. misandra (Att) 0 2 0 1 0 5 0 4 1 3 0 2 6 3 2 7 3 C. capilaris (Gr) 0 7 2 1 0 0 0 2 0 0 0 0 2 1 1 1 0 C. capilaris (Att) 0 7 0 0 0 0 0 0 0 0 0 0 3 0 1 2 0 E triste (Gr) 7 14 8 5 14 6 9 14 11 15 14 30 13 39 9 9 12 E. triste (Att) 17 17 4 15 18 9 15 16 23 9 14 62 23 41 11 13 14 Kobresia spp. (Gr) 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Kobresia spp. (Att) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 A. latifolia. (Gr) 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 1 A. latifolia (Att) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Juncus spp. (Gr) 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 Juncus spp. (Att) 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 P. viviparum (Gr) 0 0 0 0 0 2 0 3 0 0 0 0 0 0 3 1 0 P. viviparum (Att) 1 0 0 0 0 1 0 0 1 0 0 0 0 0 1 0 0 Equisetum spp. (Gr) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Saxifraga spp. (Gr) 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 Saxifraga spp. (Att) 3 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 D. integrifolia (Gr) 1 2 2 1 0 2 4 0 4 5 4 6 3 6 4 4 6 D integrifolia (Att) 0 0 2 0 0 3 4 3 10 1 5 9 3 6 8 6 12 Safe arctica (Gr) 0 0 0 0 0 1 0 0 1 0 0 4 0 0 1 0 0 Salix.arctica (Att) 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 Moss 6 6 2 0 1 4 0 15 21 2 5 1 19 6 9 24 23 Table 4.2. Plot coordinates of all major plots at Sites A , B, C, D, & E. Plot N W A l l O 78.87697 75.81324 A120 78.8769 75.8132 A130 78.87686 75.8131 A140 78.87681 75.81303 A150 78.87678 75.81301 A160 78.87674 75.81297 A11P 78.87669 75.81292 A12P 78.8769 75.81317 A13P 78.87685 75.81314 A14P 78.87681 75.81308 A15P 78.87672 75.81305 A16P 78.87673 75.81299 A21P 78.87562 75.80952 A22P 78.87558 75.80946 A23P 78.87552 75.8094 A24P 78.87547 75.80931 A25P 78.87543 75.80925 A26P 78.87538 75.80919 A3 IP 78.8759 75.81174 A32P 78.87587 75.81153 A33P 78.87583 75.81132 A34P 78.87581 75.8111 A35P 78.87576 75.81093 A36P 78.87576 75.81069 A41P 78.87598 75.81055 A42P 78.87601 75.81079 A43P 78.87604 75.81099 A44P 78.87607 75.8117 A45P 78.8761 75.8114 A46P 78.87612 75.81164 Plot N W B l l O 78.87146 75.79582 B120 78.8715 75.79576 B130 78.87155 75.79564 B140 78.87158 75.7956 B150 78.87163 75.79558 B160 78.87167 75.79553 C l l O 78.86828 75.80055 C120 78.86829 75.80076 C O O 78.86831 75.80098 C140 78.86834 75.80116 C150 78.86836 75.80134 C160 78.86838 75.80158 D U O 78.8719 75.78678 D120 78.87194 75.78681 D130 78.87199 75.78685 D140 78.87204 75.78689 D150 78.87208 75.78692 D160 78.87213 75.78694 E l l O 78.86016 75.76919 E120 78.86019 75.76928 E130 78.86024 75.76922 E140 78.86029 75.76922 E150 78.86034 75.76925 E160 78.86037 75.76928 64 4.3. Reference van Wijk MT, Clemmensen K E , Shaver GR et al. (2003) Long-term ecosystem level experiments at Toolik Lake, Alaska, and at Abisko, Northern Sweden: generalizations and differences in ecosystem and plant type responses to global change. Global Change Biology. 10, 105-123. 65 

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