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This article in SSSAJ

  1. Vol. 59 No. 4, p. 1036-1043
     
    Received: June 20, 1994


    * Corresponding author(s): schmidts@spot.colorado.edu
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doi:10.2136/sssaj1995.03615995005900040012x

Nitrogen Mineralization and Microbial Biomass Nitrogen Dynamics in Three Alpine Tundra Communities

  1. Melany C. Fisk and
  2. Steven K. Schmidt 
  1. Department of Environmental, Population, and Organismic Biology, Campus Box 334, Univ. of Colorado, Boulder, CO 80309

Abstract

Abstract

The alpine tundra of the Colorado Front Range supports a variety of plant communities whose distribution corresponds to their topographic position. Our objectives were to: (i) determine patterns in net N mineralization and microbial N pools among three communities, Kobresia, Acomastylis, and Carex meadows, that span a topographic gradient, and (ii) relate any patterns to soil microclimate differences among these communities. Average yearly net N mineralization rates, measured with an in situ core incubation technique, were 1.2 g N m−2 in 1991 and 1.0 g N m−2 in 1992. No differences were detected in yearly N mineralization rates among the three communities; however, net nitrification and other soil properties were found to differ among communities. Net N mineralization rates and microbial N showed strong temporal variation, and this variation was related to different variables for each community. Seasonal variation in N mineralization was related to soil water and microbial N in Kobresia meadows, to soil temperature and microbial N in Acomastylis meadows, and to soil water and temperature in Carex meadows. Seasonal changes in microbial N were related to soil water in Kobresia and Acomastylis meadows. Large fluctuations in microbial N indicate that periodic losses from the microbial pool may be important to N availability in this alpine tundra site.

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