期刊
SOIL BIOLOGY & BIOCHEMISTRY
卷 37, 期 8, 页码 1546-1559出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.soilbio.2005.01.016
关键词
pool dilution; microbial community composition; PLFA; nitrogen; chronosequence; lodgepole pine; gross mineralization
类别
Soils and vegetation were analyzed in 20 lodgepole pine (Pinus contorta) forest stands, varying in age from 50 to 350 years, that had initiated following stand-replacing fire. Our goal was to determine how nitrogen availability (NH4+-N) and microbial community composition varied with stand age-class and to determine whether differences could be explained by canopy, soil, or understory characteristics. Gross NH4+ mineralization was measured using laboratory isotopic pool dilution, and microbial community composition was evaluated using microbial membrane lipids. The microbial community composition of stands in the 300-350 age class was distinct from stands in younger age classes. Microbial community composition among sites varied with pH, % organic matter, and phosphorus. Gross NH4+ mineralization rates averaged 1.45 +/- 0.07 mg NH4+ kg soil(-1) d(-1) while consumption averaged 1.37 +/- 0.20 mg NH4+ kg soil(-1) d(-1), resulting in low net NH4+ mineralization rates (0.08 +/- 0.18 mg NH4+ kg soil(-1) d(-1)), but rates were not significantly different with stand age-class alp < 0.05. At p < 0.10, net NH4+ mineralization was significantly higher in the 300-350 age class compared to the 125-175 age class. None of the measured variables significantly explained NH4+ consumption and net mineralization patterns. However, gross NH4+ mineralization rates were best explained by information on microbial community structure (i.e. lipids). Variation among stands within a given age-classes was high, indicating that patterns of N cycling across landscapes reflect substantial heterogeneity among mature stands. (c) 2005 Elsevier Ltd. All rights reserved.
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