Influence of Elevated Nitrogen Deposition on Rocky Mountain Englemann Spruce Forest Nitrogen CyclingEPA Grant Number: U915431
Title: Influence of Elevated Nitrogen Deposition on Rocky Mountain Englemann Spruce Forest Nitrogen Cycling
Investigators: Rueth, Heather
Institution: Colorado State University
EPA Project Officer: Broadway, Virginia
Project Period: January 1, 1998 through January 1, 2001
Project Amount: $76,061
RFA: STAR Graduate Fellowships (1998) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems
The objective of this research project is to determine whether Englemann spruce forests closer to urban and agricultural emission sources have higher nitrogen (N) concentrations and more rapid N cycling than those farther away.
Six old-growth Englemann spruce stands east of the Continental Divide were compared with seven similar stands west of the Continental Divide. Our assumption that eastern sites receive greater N deposition than western sites is supported by National Atmospheric Deposition Program measurements for Colorado. All sites faced northeast, between 3,000-3,500 m, and had similar land-use histories and understory vegetation. The following hypotheses were tested. East slope sites have: (1) increased NO3 leaching; (2) increased foliar N, N:Mg, N:Ca, and del 15N; (3) decreased foliar lignin and lignin:N; (4) altered soil mineralization and nitrification rates; and (5) decreased soil organic matter C:N and base cations. A yearly N leaching loss index was determined using ion-exchange resin bags. Foliage and soil samples were analyzed for percent C and N, del 15N, major base cations, P, lignin, and cellulose. Soil texture, pH, and percent organic matter were measured to determine whether large site differences existed that could alter N dynamics.