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Responses of high Arctic sedge meadows to climate warning at Alexandra Fiord, Ellesmere Island, since 1980 Hill, Geoffrey E.

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 Carex, Eriophorum, Dryas and Polygonurn (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.

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