15N enrichment as an integrator of the effects of C and N on microbial metabolism and ecosystem function.
Organic carbon (C) and nitrogen (N) are essential for heterotrophic soil microorganisms, and their bioavailability strongly influences ecosystem C and N cycling. We show here that the natural (15)N abundance of the soil microbial biomass is affected by both the availability of C and N and ecosystem N processing. Microbial (15)N enrichment correlated negatively with the C : N ratio of the soil soluble fraction and positively with net N mineralization for ecosystems spanning semiarid, temperate and tropical climates, grassland and forests, and over four million years of ecosystem development. In addition, during soil incubation, large increases in microbial (15)N enrichment corresponded to high net N mineralization rates. These results support the idea that the N isotope composition of an organism is determined by the balance between N assimilation and dissimilation. Thus, (15)N enrichment of the soil microbial biomass integrates the effects of C and N availability on microbial metabolism and ecosystem processes.
Dijkstra
Paul
P
Department of Biological Sciences, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011, USA. paul.dijkstra@nau.edu
LaViolette
Corinne M
CM
Coyle
Jeffrey S
JS
Doucett
Richard R
RR
Schwartz
Egbert
E
Hart
Stephen C
SC
Hungate
Bruce A
BA
D002244:Carbon / Q000032:analysis*; D002980:Climate; D017753:Ecosystem; D009584:Nitrogen / Q000032:analysis*; D009587:Nitrogen Isotopes / Q000032:analysis*; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D013997:Time Factors
D009587:Nitrogen Isotopes; D012987:Soil; D002244:Carbon; D009584:Nitrogen