PARENT SESSION
Oral Session #21: Nutrient cycling: Nitrogen.
Presiding: S. Hart
Monday, August 5. 1:00 PM to 3:45 PM. Grand Ballroom Central, Radisson.
Watershed controls on streamwater nitrate concentrations, Catskill Mountains, NY.
WEATHERS, KATHLEEN*,1, LOVETT, GARY1, ARTHUR, MARY2, SIMKIN, SAMUEL1, 1 INSTITUTE OF ECOSYSTEM STUDIES, MILLBROOK, NY2 UNIVERSITY OF KENTUCKY, LEXINGTON, KY
ABSTRACT- Nitrate concentration in streamwater varies 17-fold among small, forested watersheds in the Catskill Mountains, NY. Many factors are likely to influence nitrogen export and retention at the scale of watersheds, including topography, atmospheric deposition, groundwater input, forest growth rate or net ecosystem production, forest history and species composition. We examined the influence of several of these factors on nitrate concentrations in streamwater in 39 watersheds using regression analysis with a GIS database that included land use history, vegetation type, topography, and atmospheric deposition. Fifty percent of the variance in the nitrate concentrations across watersheds was attributable to the percent area of oak-dominated (Quercus spp.) forest in the watershed (r 2 = 0.50, p<0.0001), even though no watershed had >30% oak. The relationship between landuse history and nitrate concentrations was consistent with biogeochemical theory: percent old growth forest was positively related to nitrate concentrations in streamwater (r 2=0.13, p=0.02). Stand-level studies further confirm the potential importance of tree species in influencing nitrogen retention and nitrogen export in Catskill watersheds. Species differed significantly in nitrification potential (p<0.0001), with oak having among the lowest rates. We suggest that in the Catskill Mountains, watersheds comprised of different forest types, especially those dominated by oaks, are likely to have qualitatively different N cycling and retention of N deposited from the atmosphere.
KEY WORDS: catskills, oak, nitrogen, watershed