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Nitrogen Incorporation and Flow Through a Coniferous Forest Soil Profile
Author(s) -
Schimel Joshua P.,
Firestone Mary K.
Publication year - 1989
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1989.03615995005300030025x
Subject(s) - detritus , cycling , forest floor , soil horizon , biomass (ecology) , nutrient cycle , nitrogen cycle , nitrogen , environmental science , horizon , environmental chemistry , soil science , ecosystem , chemistry , soil water , botany , ecology , hydrology (agriculture) , biology , geology , forestry , mathematics , geometry , organic chemistry , geotechnical engineering , geography
One of the major controls on N cycling in forest ecosystems is the dynamics of N in the forest floor. Uptake and movement of NH + 4 by the microbial component of a mixed conifer forest soil in central California were examined by injecting 15 NH + 4 into either the O2 or the A horizon. Distribution of the tracer was constrained by 15 × 30 cm cylinders placed in situ 1.5 yr prior to the experiment. The 15 N was followed over 1‐ and 31‐d periods to measure both the short‐term uptake and the longer‐term fate of N. Recovery of 15 N was determined in coarse roots, coarse woody detritus, fine detritus, fungal strands, and the bulk soil in each horizon; microbial biomass 15 N was determined in the A horizon only. Nitrogen‐dynamics in the forest floor were characterized by a period of rapid microbial NH + 4 ‐uptake after which transformations were slower. The rate of NH + 4 immobilization was approximately 200 mg m −2 d −1 , giving a turnover time for the NH + 4 pool of less than 1 d. In the A horizon, there was no conversion of microbial 15 N into soil organic 15 N, but there was extensive lateral translocation of 15 N from microbial biomass in the bulk soil into coarse dead roots and coarse detritus. There was little vertical translocation up the profile from either the O2 or the A horizons. This work indicates the rapidity of N turnover in the forest floor and suggests that N sequestering in woody residues may be an important fate of N in this forest soil.