Experimental Increases in Snow Depth Alters the Seasonality, Structure and Function of Ecosystems in Alaska and Greenland

Establishing how changes in winter snow depth can alter the seasonality and magnitude of important feedback processes, linkages between trophic levels and connectivity between terrestrial and aquatic ecosystems is central to understanding tundra ecosystems of the future. For the past 15 years we have carried out an extensive set of Low and High Arctic snow depth manipulations, including a new set of experiments as part of IPY. We will discuss our most important findings, including a new framework for a collaborative Pan Arctic Snow Experiment Network (PASEN). Our studies indicate that: 1) modest increases in snow depth (2-3X) stimulate shrub expansion, while large increases (5-6X) in snow depth lead to permafrost thawing and the release of old carbon; 2) higher rates of winter N mineralization under deeper snow leads to higher leaf N in many plant species during the subsequent summer, a change that is associated with greater forage quality and higher rates of ecosystem carbon fixation. It is worth noting that deeper snow shifts the timing of maximum leaf N by up to 2 weeks, a change that may disrupt plant-herbivore relations; 3) deeper snow increases the concentration of DOC in soils which can lead to the transfer of carbon from terrestrial to aquatic systems, altering the biogeochemistry of streams and rivers. We believe that a continued emphasis on Arctic winter biogeochemical processes is needed throughout the North and is central to understanding the future Arctic system. This can be accomplished by establishing a PASEN, with a common set of monitoring and process-level studies.