TY - JOUR
T1 - Variation in NH4+ mineralization and microbial communities with stand age in lodgepole pine (Pinus contorta) forests, Yellowstone National Park (USA)
AU - Smithwick, Erica A.H.
AU - Turner, Monica G.
AU - Metzger, Kristine L.
AU - Balser, Teri C.
N1 - Funding Information:
Funded by a grant from the Andrew W. Mellon Foundation's Conservation and the Environment Program to Dr Monica G. Turner. We thank Ryosuke Fujinuma for substantial laboratory assistance and guidance, Harry Read for running the gas chromatograph for PLFA analysis, and Daniel Kashian for assistance with site selection and for data on tree density, basal area increment, and leaf area index. We also thank Jun Zhu for statistical consultation.
PY - 2005/8
Y1 - 2005/8
N2 - 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 NH 4+ 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 at p<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 NH 4+ 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.
AB - 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 NH 4+ 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 at p<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 NH 4+ 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.
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U2 - 10.1016/j.soilbio.2005.01.016
DO - 10.1016/j.soilbio.2005.01.016
M3 - Article
AN - SCOPUS:20344392691
SN - 0038-0717
VL - 37
SP - 1546
EP - 1559
JO - Soil Biology and Biochemistry
JF - Soil Biology and Biochemistry
IS - 8
ER -