Potential climate change scenario on soil biogeochemical processes at Hubbard Brook Experimental Forest

*Samuel F. T. Fashu-Kanu and Charles T. Driscoll

Civil and Enviromental Engineering Department, Syracuse University

220 Hinds Hall, Syracuse, New York, 13244

Anthropogenic release of greenhouse gases has been implicated in global climate change which could result in an increase in the global mean surface temperature of 4.5 °F (2.5°C) by the middle of the century.  Future climatic scenarios suggest that there will be a reduction in the frequency, duration and amount of snowfall in the middle latitudes that could inadvertently cause extensive soil freezing and increase the freeze thaw cycle and water dynamics, thereby severely impacting the biogeochemical cycles in northern ecosystems.  If soil freezing becomes more common with global warming it could become an important regulator of microbial activities, nutrient cycling, loss and retention, surface water acidification, changes in soil atmosphere trace gas fluxes, uptake processes and forest tree species composition in northern forest ecosystems.   In this experiment, the interactions between soil freezing disturbances, elevation and aspect on soil solution chemistry at Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA was conducted in 2003/2004.  The soil solution chemistry was collected from the humus (Oa horizons) and mineral (Bs horizons) of randomly designated adjacent paired treatment and reference subplots, each 10 m X 10 m, from each of four sites; East Mt. Kineo, West Mt. Kineo, lower valley and upper valley plots to maximize spatial variability. Treatment plots were kept snow free by shoveling in January 2003/2004 and February 2003/2004 while the reference plots were allowed to accumulate snow at the normal rate.  There is evidence of treatment effect at the Upper Valley and the West Kineo plots.  Soil solution from organic (Oa) horizon responded more than Bs horizon and there was response to soil freezing across the different elevation climate gradient.  The results also indicate a close correlation between soil freezing, elevation, aspect and soil solution chemistry.  Climate change towards less snow will result in a shorter duration of snow on the ground that will produce increases in soil freezing in northern hardwood forests and increases in soil freezing will have implications for changes in soil biogeochemical processes.