Controls on nitrogen flux in alpine/subalpine watersheds of Colorado

Donald H. Campbell, Jill S. Baron, Kathy A. Tonnessen, Paul Brooks, Paul F. Schuster

Research output: Contribution to journalArticle

98 Citations (Scopus)

Abstract

High-altitude watersheds in the Front Range of Colorado show symptoms of advanced stages of nitrogen excess, despite having less nitrogen in atmospheric deposition than other regions where watersheds retain nitrogen. In two alpine/subalpine subbasins of the Loch Vale watershed, atmospheric deposition of NO3/- plus NH4/+ was 3.2-5.5 kg N ha-1, and watershed export was 1.8-3.9 kg N ha-1 for water years 1992-1997. Annual N export increased in years with greater input of N, but most of the additional N was retained in the watershed, indicating that parts of the ecosystem are nitrogen-limited. Dissolved inorganic nitrogen (DIN) concentrations were greatest in subsurface water of talus landscapes, where mineralization and nitrification augment high rates of atmospheric deposition of N. Tundra landscapes had moderately high DIN concentrations, whereas forest and wetland landscapes had low concentrations, indicating little export of nitrogen from these landscapes. Between the two subbasins the catchment of Icy Brook had greater retention of nitrogen than that of Andrews Creek because of landscape and hydrologic characteristics that favor greater N assimilation in both the terrestrial and aquatic ecosystems. These results suggest that export of N from alpine/subalpine watersheds is caused by a combination of direct flushing of N from atmospheric deposition and release of N from ecosystem biogeochemical processes (N cycling). Sensitivity of alpine ecosystems in the western United States to atmospheric deposition of N is a function of landscape heterogeneity, hydrologic flow paths, and climatic extremes that limit primary productivity and microbial activity, which, in turn, control retention and release of nitrogen. Conceptual and mechanistic models of N excess that have been developed for forested ecosystems need to be modified in order to predict the response of alpine ecosystems to future changes in climate and atmospheric deposition of N.

Original languageEnglish (US)
Pages (from-to)37-47
Number of pages11
JournalWater Resources Research
Volume36
Issue number1
DOIs
StatePublished - 2000
Externally publishedYes

Fingerprint

Watersheds
atmospheric deposition
Nitrogen
watershed
Fluxes
nitrogen
Ecosystems
ecosystems
ecosystem
dissolved inorganic nitrogen
talus
Western United States
mechanistic models
tundra
flushing
terrestrial ecosystem
nitrification
Aquatic ecosystems
microbial activity
aquatic ecosystem

ASJC Scopus subject areas

  • Aquatic Science
  • Environmental Science(all)
  • Environmental Chemistry
  • Water Science and Technology

Cite this

Controls on nitrogen flux in alpine/subalpine watersheds of Colorado. / Campbell, Donald H.; Baron, Jill S.; Tonnessen, Kathy A.; Brooks, Paul; Schuster, Paul F.

In: Water Resources Research, Vol. 36, No. 1, 2000, p. 37-47.

Research output: Contribution to journalArticle

Campbell, DH, Baron, JS, Tonnessen, KA, Brooks, P & Schuster, PF 2000, 'Controls on nitrogen flux in alpine/subalpine watersheds of Colorado', Water Resources Research, vol. 36, no. 1, pp. 37-47. https://doi.org/10.1029/1999WR900283
Campbell, Donald H. ; Baron, Jill S. ; Tonnessen, Kathy A. ; Brooks, Paul ; Schuster, Paul F. / Controls on nitrogen flux in alpine/subalpine watersheds of Colorado. In: Water Resources Research. 2000 ; Vol. 36, No. 1. pp. 37-47.
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