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: Hahn, Intaek
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
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.