title: In situ estimates of annual net nitrogen mineralization and nitrification in a subarctic watershed.
abstract: 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-1yr-1for 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-1yr-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.
authors.affiliation: Department of Plant and Soil Biology, University of California, 94720, Berkeley, CA, USA.|Energy and Resources Group, University of California, 94720, Berkeley, CA, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Hart
authors.affiliation: Department of Plant and Soil Biology, University of California, 94720, Berkeley, CA, USA.|Energy and Resources Group, University of California, 94720, Berkeley, CA, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Gunther
keywords: Alder; Nitrogen availability; Substrate qualitity; Tundra; Volcanic ash; White spruce