9400083 Walker This project will evaluate the ecological consequences of climate change in moist and dry arctic tundra with field manipulations of winter precipitation and summer temperature. Project scientists will investigate effects on species performance, community structure, and ecosystem C and N dynamics. They will erect snow fences to increase snowpack and use small greenhouses to warm air and soil temperatures. Growth rings and annual stem increments of woody species and physiological plant performance will be compared with historical temperature and precipitation records. Experimental findings will also be compared to natural vegetation patterns along snow gradients and areas where long-term anthropogenic increases in snow cover have occurred. Simulation modeling will be used to extend their findings with a focus on net ecosystem carbon budgets. The main effort will be to quantify and understand the magnitude and direction of the transient response of arctic tundra to a series of climate change scenarios. The experimental infrastructure will permit more detailed investigations by other investigators in future years if the response is, as we anticipate, of sufficient magnitude to be of importance for evaluating effects of climate change to arctic ecosystems. The project is a U.S. contribution to the International Tundra Experiment (ITEX). ***
