Responses of plants to warming at
In july, I will set up a new full-factorial field experiment together with CENPERM Professor Anders Michelsen in a tundra shrub heath on Disko Island, W-Greenland. The aim of our study is to measure the effects of seasonal warming on carbon and nitrogen cycling through plants, permafrost and microbes. As of yet, much is unknown about the impacts of seasonal warming events on tundra ecosystems. It is important to generate more knowledge about the effects of climate warming on the sensitive Arctic tundra ecosystem as changes in high latitudes may feedback to the global climate through release of greenhouse gases and through changes in surface conditions by shifts in plant cover. Previously, most research has focused on the effects of summer warming on tundra vegetation and soil microbial processes. However, most of the warming that is predicted for the coming century will likely occur during the winter period. By locally elevating the snow height using snow fences we will mimic predicted increases in winter precipitation and raise winter soil temperatures through the insulating effect of snow compared to control plots with ambient snow levels. Summer soil temperatures will be raised in selected plots using Plexiglas Open-Top Chambers. Finally, we will evaluate the cooling effect of shrub canopies on summer soil conditions by clipping the shrub biomass from half of the plots. Shrubs are known to profit from higher air temperatures by growing denser and taller, and thus potentially providing a negative feedback to permafrost warming by shading the soil surface and lowering soil temperatures. Our experiment will provide a unique opportunity to test both the effects of winter and summer warming, as well as summer soil cooling on plant growth and exchange of carbon and nitrogen through permafrost, plants and microbes.