Soil biogeochemical response to and recovery from in situ simulated climate induced soil freezing across spatial and temporal scales at a northeastern watershed S.F.T. Fashu-Kanu ,C.T. Driscoll, P. M Groffman, J.P. Hardy, T.J. Fahey Civil Engineering, Syracuse University, Syracuse, NY 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.    What is the effect of climate induced soil freezing disturbance on soil solution chemistry, trace gases, microbial biomass and N transformation processes across spatial gradient and temporal scales at Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA.  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.  Soil solution chemistry, trace gas fluxes, microbial biomass and transformation processes response to treatment varied across spatial boundaries and temporal scales. Treatment response at the sugar maple dominated upper valley and West Kineo plots were stronger relative to yellow birch dominated sites, at high relative to low elevation plots and at the organic relative to mineral soil horizon. There was also a strong correlation between soil freezing, elevation, vegetation type, horizon, season and year with soil biogeochemistry. Further, soil biogeochemical recovery from freeze treatment effect was evident a year after the discontinuation of the treatment across spatial boundaries and temporal scales. The indication was that global warming from changing climate could significantly impact biogeochemical cycles and result in shorter duration of snow on the ground that will increase the frequency and duration of soil freezing in northern ecosystems with implication for soil biogeochemical processes. However, control of the effect may result in response reduction within a short period.