Effects of long-term experimental warming on high Arctic soil seed banks

Predictions that climate warming will enhance plant sexual reproduction in the High Arctic were examined using an experimental warming field study located in the eastern Canadian High Arctic.  Small open top chambers (OTCs), which simulate climate warming, were established in 1992 within tundra plant communities along a soil moisture gradient at Alexandra Fjord, Ellesmere Island.  In 2004, soil seed bank samples were collected from warmed and control plots.  Seeds were germinated, and the total number of germinants were used as a measure of response to long-term experimental warming. OTCs increased within-plot growing season air temperatures by 1 - 2^oC, which is within range of general circulation model (GCM) predictions for climate warming in the Arctic.  Warming also advanced dates of snowmelt and extended the growing season in most soil moisture regimes.  The total number of germinants increased under warmed conditions, but responses were species-specific and depended on soil moisture levels.  Differences between warmed and control plots indicate the potential for altered plant recruitment, which could lead to important changes in tundra plant communities, particularly if rates of seedling establishment also increase.