In situ estimates of annual net nitrogen mineralization and nitrification in a subarctic watershed |
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Authors: | S C Hart A J Gunther |
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Institution: | (1) Department of Plant and Soil Biology, University of California, 94720 Berkeley, CA, USA;(2) Energy and Resources Group, University of California, 94720 Berkeley, CA, USA;(3) Present address: 180 Richmond Field Station, Aquatic Habitat Institute, 1301 South 46th Street, 94804 Richmond, CA, USA |
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Abstract: | Summary Annual estimates of surface soil nitrogen transformations were determined using an in situ method in four different subarctic vegetation types within a watershed in southwestern Alaska. The net nitrogen mineralization estimates were 22.5, 0.5, 4.7, and 2.7 kg-N ha-1 yr-1 for the alder, dry tundra, moist tundra, and white spruce sites, respectively. Only the soil from the alder site showed net nitrification (about 10 kg-N ha-1 yr-1). Annual inogranic nitrogen flux from the overlying organic layer to the mineral soil was almost seven times greater than net N production in the surface mineral soil in the alder site, indicating that the alder forest floor is potentially a substantial source for plant-available N. Rates of mobilization of N from the surface organic layers of the other sites were similar to net N production rates in surface mineral soils. In situ rates of N transformations showed a similar trend among sites as did laboratory estimates conducted in a previous study, suggesting a strong substrate control of N transformations in these soils. |
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Keywords: | Alder Nitrogen availability Substrate qualitity Tundra Volcanic ash White spruce |
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