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Soil nitrogen dynamics following harvesting and conversion of red alder and Douglas fir stands

Journal Article · · Soil Science Society of America Journal; (United States)
 [1];  [2];  [3]
  1. Oak Ridge National Lab., TN (United States)
  2. Oregon State Univ., Corvallis, OR (United States)
  3. Univ. of Washington, Seattle, WA (United States)

Drastic reductions in NO[sub 3][sup [minus]] leaching have been observed after harvesting of mature red alder (Alnus rubra Bong.) stands. Our objective was to examine whether these reduction were linked to changes in soil N dynamics. Adjacent alder and Douglas fir [Pseudotsuga menziessii (Mirbel.) Franco] stands on young glacial soils (Alderwood; a loamy-skeletal, mixed, mesic, ortstein Aquic Haplorthod) in western Washington were harvested and replanted with either alder or Douglas fir seedlings; reference plots were established in nearby undisturbed stands. Three years after site conversion, when NO[sub 3][sup [minus]] leaching declined most drastically in the harvested alder plots, net N mineralization and net nitrification in the upper soil were determined seasonally by in situ incubation using the buried-bag technique. There were no significant increases in soil NH[sub 4]-N during incubation, indicating that nitrification rates closely followed net N mineralization in all plots. In the N-poor soils of the harvested and uncut Douglas fir plots, nitrification was consistently <2 [mu]g N g[sup [minus]1] per 30 d. In the N-rich alder reference plot, nitrification was highest in summer (52 [mu]g N g[sup [minus]1] per 30 d), lowest in winter (4 [mu]g N g[sup [minus]1]), and intermediate in spring (20 [mu]g N g[sup [minus]1]). Seasonal fluctuations in nitrification diminished in the harvested alder plots. 52 refs., 8 figs., 1 tab.

DOE Contract Number:
AC05-84OR21400
OSTI ID:
5647847
Journal Information:
Soil Science Society of America Journal; (United States), Journal Name: Soil Science Society of America Journal; (United States) Vol. 56:4; ISSN 0361-5995; ISSN SSSJD4
Country of Publication:
United States
Language:
English