Snow Depth, Soil Frost, and Nutrient Loss
in a Northern Hardwood Forest
Peter M. Groffman1, Janet P. Hardy2, Scott Nolan3,
Charles T. Driscoll4, and Timothy J. Fahey5
A lack of snow cover results in colder soil temperatures, more extensive soil freezing, and an in-
crease in freeze/thaw cycles. Previous studies have suggested (but not verified) that these stresses
result in root and microbial mortality, releasing labile organic carbon and nitrogen to soil (via root
and microbial death) and increasing soil moisture and available N (via reduced uptake by trees and
microbes). These changes lead to increases in net mineralization and nitrification rates, nitrate
-
believe that differential resistance to freezing stress will be a key regulator of species composition
in northern forests under a warmer climate condition.
We have initiated a long-term experiment to examine the consequences of decreases in snowpack
accumulation at the Hubbard Brook Experimental Forest (HBEF), a northern-hardwood-dominated
forest located in the White Mountains of New Hampshire. We are quantifying the effects of
decreases in snowpack accumulation on root dynamics of-two key tree species in this forest (sugar
maple, yellow birch), microbial biomass and activity, NO3 and cation loss, the acid-base chemistry
of drainage water, and soil- atmosphere trace gas fluxes. We are calibrating an existing model
(SNTHERM) that depicts snow depth and 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 studies that began in the
winter of 1997/1998 and present preliminary results from pilot studies conducted during the winter
of 1996/1997. Results from the pilot studies show that the SNTHERM model is capable of depicting
snow depth and soil temperatures in our plots and that a six-week midwinter snow removal treat-
ment led to significant increases in early spring soil inorganic N levels. In a more practical sense,
results from the pilot studies suggest that it is quite feasible to keep plots snow free by shoveling,
without disturbing the forest floor. The pilot studies results also show that snow removal will in-
duce soil freezing and effects on soil N dynamics, even if air temperatures are not extremely low.
1
Institute of Ecosystem Studies, Box AB, Millbrook, New York 12545, USA
2
U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire 03755, USA
3
Institute of Ecosystem Studies, Hubbard Brook Experimental Forest, Campton, New Hampshire 03223,
USA
4 Syracuse University, Department of Civil and Environmental Engineering, Syracuse University, Syracuse,
New York 13244, USA
5 Cornell University, Department of Natural Resources, Ithaca, New York 14853, USA
27
Previous Page
