Natural variability in N export from headwater catchments: Snow cover controls on ecosystem N retention

Paul Brooks, Don H. Campbell, Kathy A. Tonnessen, Kristi Heuer

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

The causes of natural variability in catchment scale N export need to be understood and quantified before the effects of increased N deposition in high elevation catchments can be evaluated. This study evaluates controls on the size of the leachable soil N pool concurrent with the spring hydrologic flush that is primarily responsible for the transport of N to surface water. In high elevation catchments in the western United States, sources of N during this snowmelt flush include both atmospheric N deposition stored in the snowpack until melt and mobile soil N pools, and sinks are dominated by biogeochemical processes that occur in soil under snow cover. Because soil processes may serve either as a source or sink for N, controls on the amount of inorganic N leached from soil during the snowmelt period were evaluated in the major landscape types in four catchments in Colorado. Measurements of leached N were inversely related to measurements of over-winter CO2 flux at all sites, indicating that N was immobilized in soil heterotrophic biomass. Because over-winter soil heterotrophic activity is controlled primarily by the depth and timing of snow accumulation, the importance of these plot scale measurements to catchment scale N export were evaluated using a long-term record of winter precipitation, N deposition, and N export from Loch Vale in Rocky Mountain National Park. This data set identified a strong, linear relationship (r2 = 0·68) between catchment scale N retention and winter snow cover, consistent with subnivean, soil based controls on the mobile N pool identified at the plot scale. These results indicate that the winter snow pack is the major control both on hydrologic N export and on soil source/sink relationships for N concurrent with this transport mechanism. The effect of winter snow cover on the fate of both atmospheric and soil N needs to be considered when evaluating potential the effects of increased N deposition on either terrestrial or aquatic ecosystems in seasonally snow-covered watersheds. In these systeems, changes in surface water chemistry are likely to occur in high deposition, snow-covered sites during low years before terrestrial vegetation is affected.

Original languageEnglish (US)
Pages (from-to)2191-2201
Number of pages11
JournalHydrological Processes
Volume13
Issue number14-15
StatePublished - Oct 1999
Externally publishedYes

Fingerprint

snow cover
headwater
catchment
ecosystem
soil
winter
snow
snowmelt
surface water
snow accumulation
snowpack
terrestrial ecosystem
water chemistry
aquatic ecosystem
national park
melt
watershed
mountain
vegetation
biomass

Keywords

  • Catchment biogeochemistry
  • Headwater catchments
  • Nitrogen cycling
  • Nitrogen saturation
  • Snow cover
  • Snowmelt

ASJC Scopus subject areas

  • Water Science and Technology

Cite this

Natural variability in N export from headwater catchments : Snow cover controls on ecosystem N retention. / Brooks, Paul; Campbell, Don H.; Tonnessen, Kathy A.; Heuer, Kristi.

In: Hydrological Processes, Vol. 13, No. 14-15, 10.1999, p. 2191-2201.

Research output: Contribution to journalArticle

Brooks, Paul ; Campbell, Don H. ; Tonnessen, Kathy A. ; Heuer, Kristi. / Natural variability in N export from headwater catchments : Snow cover controls on ecosystem N retention. In: Hydrological Processes. 1999 ; Vol. 13, No. 14-15. pp. 2191-2201.
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