Document: PAM-3-59-10

Effect of tree species on nitrogen retention in the Catskill Mountains, NY: ¹⁵N Studies.

TEMPLER, P.* ^1,2, G.LOVETT ², K.WEATHERS ², S.FINDLAY ² and T.DAWSON ³

Cornell University, Ithaca, NY 14853 USA ¹
Institute of Ecosystem Studies, Millbrook, NY 12545 USA ²
University of California Berkeley, Berkeley, CA USA ³

Abstract:
This study examines the role that dominant tree species play in the nitrogen (N) retention of forested watersheds in the Catskill Mountains. These forests receive high rates of atmospheric N deposition causing export of increasing amounts of N to streams. There is a 27-fold difference in stream nitrate concentration among 39 watersheds even though N deposition is approximately uniform. To examine whether trees, and the soil microbes associated with them, vary in their capacity for N retention, we added a ¹⁵N tracer to four plots within stands of American beech, sugar maple and eastern hemlock during summer 1998. We collected soil from each of the 12 plots at 1, 3, 13 and 45 days following N addition. Per unit area, soils associated with hemlock had a significantly higher amount of total dissolved N, microbial biomass N, root N (p<0.05) and microbial uptake of 15N (p<0.05). Total soil pools of N (per g soil and per unit area) in hemlock were more than two times higher than the amount found in sugar maple and American beech (p<0.05). These results suggest that soil pools of N are higher in soils associated with the evergreen tree species, hemlock, than those associated with the deciduous tree species, American beech and sugar maple. Results from this project will help determine the role that dominant tree species play in the N retention of watersheds.

Keywords: nitrogen, tree species, forest, watershed retention

This abstract is being presented at: 11:00 AM in session:
Oral Session #41: N Dynamics: Additions, Retention and Transformations.