Soil freezing dynamics in a changing climate: implications for soil nitrogen dynamics
TUESDAY, MARCH 5TH, 2013 - 1:30PM IN EIT 3142 AT THE UNIVERSITY OF WATERLOO
The responses of soils to climate change over winter are complicated by interactions between air temperature and snow cover, which both influence the magnitude and dynamics of soil freezing. I examined projections of soil freezing responses to climate change obtained using a variety of modeling, observational and hindcasting approaches. Overall, despite a general pattern of a decreased numbers of days of frozen soil and decreased numbers of days with snow on the ground, projected responses of soil freezing dynamics to climate change have been regional in nature. Specifically, while southern temperate regions that currently experience mild winters will likely cease to experience soil freezing in some years, many northern temperate regions may experience an increased number of soil freeze thaw cycles as a result of reduced snow cover. The responses of soil nitrogen dynamics to changes in soil freezing are sensitive to the timing, frequency, length and severity of soil freeze-thaw cycles. Severe soil freezing can lyse soil microorganisms and roots, increasing N leaching and trace gas losses at snow melt. In addition, freezing damage to root systems can reduce soil N retention over the following growing season. I describe how soil incubations and N tracers have been used to explore which N pools contribute to these losses, how this may change seasonally and how freezing damage might interact with increases in atmospheric N deposition over the next century.