Snow depth, soil frost and nutrient loss in a northern hardwood forest

We have initiated a long-term experiment to examine the consequences of dec reases in snowpack accumulation at the Hubbard Brook Experimental Forest (H BEF), a northern hardwood dominated forest located in the White Mountains o f New Hampshire. We are quantifying the effects of decreases in snowpack ac cumulation on root dynamics of two key tree species in this forest (sugar m aple, yellow birch), microbial biomass and activity, NO3- and cation loss, the acid-base chemistry of drainage water, and soil-atmosphere trace gas fl uxes. We are calibrating an existing model (SNTHERM) to depict snow depth a nd soil frost dynamics given past or future climate scenarios for our site. In this paper, we describe the methods we are using for the manipulation s tudies that began in the winter of 1997/1998 and present preliminary result s from our first full year of treatment. Results from our methods developme nt efforts show that it is possible to keep plots snow free by shovelling w ithout disturbing the forest floor. Preliminary test plot work showed that the SNTHERM model is capable of depicting snow depth and soil temperatures in both control and manipulated plots at our site. Results from our first f ull year of treatment showed that a relatively mild freezing event induced significant increases in nitrogen (N) mineralization and nitrification rate s, solute leaching and soil nitrous oxide production and caused significant decreases in soil methane uptake. These results suggest that soil freezing events may be major regulators of soil biogeochemical processes and solute delivery to streams in forested watersheds. Copyright (C) 1999 John Wiley & Sons, Ltd.