What was done
The authors investigated changes in the above- and below-ground biomass of wet sedge tundra to the warming climate of the Canadian High Arctic over the past 25 years. This was done on the coastal lowland of Alexandra Fiord, Ellesmere Island, Nunavut, Canada, where between 1980 and 1984 Henry (1987) and Henry et al. (1990) studied wet sedge meadow ecosystems, while establishing, in their words, "one of Canada's oldest comprehensive Arctic tundra studies (Svoboda and Freedman, 1994)." More specifically, as they describe it, "wet sedge tundra sites were analyzed for long-term response to climate change by comparing above- and below-ground biomass harvests and soil samples taken in 1980-1983 with repeated measurements using the same methods at five of the same sites in 2005."

What was learned
The two Canadian researchers determined that "aboveground biomass was on average 158% greater in 2005 than in the early 1980s," and they say that "belowground biomass was also much greater in 2005: root biomass increased by 67% and rhizome biomass by 139% since the early 1980s." In addition, they report that "dominant species from each functional group (graminoids, shrubs and forbs) showed significant increases in aboveground biomass," and that "responsive species included the dominant sedge species Carex aquatilis stans, C. membranacea, and Eriophorum angustifolium, as well as the dwarf shrub Salix arctica and the forb Polygonum viviparum."

What it means
Hill and Henry say that the increase in biomass they measured "indicates that the long-term ambient warming has stimulated the accumulation of carbon in this system," and that it "likely affected the sedge meadows mainly indirectly through a suite of nutrient enhancing factors including increased decomposition and mineralization rates and/or duration, and enhanced nutrient pools," citing the supporting work of Shaver et al. (2001), Rolph (2003) and Sullivan et al. (2008). And they make a special point of noting that "this conclusion is in opposition to the hypothesis that infertile grasslands are resistant to climate change (Grime et al., 2008)."

References
Grime, J.P., Fridley, J.D., Askew, A.P., Thompson, K., Hodgson, J.G. and Bennett, C.R. 2008. Long-term resistance to simulated climate change in an infertile grassland. Proceedings of the National Academy of Sciences USA 105: 10,028-10,032.

Henry, G.H.R. 1987. Ecology of Sedge Meadow Communities of a Polar Desert Oasis: Alexandra Fiord, Ellesmere Island, Canada. PhD Dissertation, University of Toronto, Toronto, Canada.

Henry G.H.R., Freedman, B. and Svoboda, J. 1990. Standing crop and net production of ungrazed sedge meadows of a polar desert oasis. Canadian Journal of Botany 68: 2660-2667.

Rolph, S.G. 2003. Effects of a Ten-Year Climate Warming Experiment on Nitrogen Cycling in High Arctic Tundra. MSc Dissertation, University of British Columbia, Vancouver, Canada.

Shaver, G.R., Bret-Harte, S.M., Jones, M.H., Johnstone, J., Gough, L., Laundre, J. and Chapin, F.S. 2001. Species composition interacts with fertilizer to control long-term change in tundra productivity. Ecology 82: 3163-3181.

Sullivan, P.F., Arens, S.J.T., Chimner, R.A. and Welker, J.M. 2008. Temperature and microtopography interact to control carbon cycling in a High Arctic fen. Ecosystems 11: 61-76.

Svoboda, J. and Freedman, B., Eds. 1994. Ecology of a Polar Desert Oasis. Captus University Press, Toronto, Canada.