Jennifer Liebig ACF Abstract FY13

"Community Change in Long-term Vegetation Monitoring Sites in Northern Alaska"

American Geophysical Union (AGU) Fall Meeting

Vegetation in the Arctic is changing in response to global climate change. Warming in high latitudes has been documented and is expected to continue. With data from sites established in the mid-1990s, we can predict how Arctic vegetation will continue to change using observed changes from both ambient and experimental warming. The four sites are in northern Alaska, where there is a wet meadow site and a dry heath site in Barrow (71°172443N 156°452593W) and a wet meadow site and a dry heath site in and in Atqasuk (70°2840N 157°25253W). Each consists of 24 experimental plots warmed by passive open-topped warming chambers and 24 control plots. The cover of plant species was sampled using a point-frame method four times from the establishment of the sites until the most recent sampling in 2012. The change in cover in response to warming was assessed individually for each species. These data were then lumped into different grouping schemes based on traits that could potentially be used to predict response. A two-way ANOVA was used to compare difference in cover among groups between the warmed and control plots. If the groups within a grouping scheme responded significantly differently to the warming treatment (i.e., there was an interaction between warming treatment and grouping scheme), then that grouping scheme was considered useful for predicting change in tundra communities. Of the grouping schemes used for this analysis, some were based on geographic distribution, such as distribution zones defined by Young 1971, some were based on phenology of the species, such date of flower opening as observed in these sites, and some were based on other morphological and life history traits, such as the wintering state of buds as defined by Sørensen 1971. Overall, the response to warming by species with particular traits varied from site to site, as did the usefulness of an individual grouping scheme. The observed changes may be driven by the increase or decrease in cover of a few abundant species, Carex aquatilis in particular. These grouping schemes are useful for increasing our understanding of how and why community composition is changing; however, a more complex grouping system that combines different traits is needed to more fully understand and better predict the response of Arctic plant species to warming.