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Soil nitrogen status as a regulator of carbon substrate flows through microbial communities with elevated CO2
Ziegler, Susan E. Billings, Sharon A.
Ziegler, Susan E.
Billings, Sharon A.
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Abstract
To assess how microbial processing of organic C inputs to forest soils may be
influenced by elevated CO2 and altered N dynamics, we followed the fate of 13C‐labeled
substrates in soils from the Duke Free Air Carbon Enrichment site where differences in
soil N status have been imposed by 7 years of N amendments. Heterotrophic respiration
and d13C of respired CO2‐C and phospholipid fatty acids (PLFA) were measured to
track activities of microbial groups and estimate a relative measure of substrate use
efficiency (PLFA‐based SUE). Results indicate an increased proportion of fungal and
actinomycete activity in elevated CO2 soils, which varied with substrate. The negative
effect of N on vanillin phenolic‐C incorporation into actinomycete PLFA suggests legacies
of fertilization can mitigate increased C flow into actinomycetes with elevated CO2.
Further, the fourfold increase in PLFA‐based SUE for vanillin phenolic‐C in elevated CO2
soils that received N suggests future enhanced N limitation in elevated CO2 soils may
promote enhanced respiratory loss relative to incorporation of some C‐substrates into
microbial biomass. These short‐term incubations did not reveal greater loss of soil organic
carbon via respiration or shifts in SUE with elevated CO2. However, observed relative
increases in activity of actinomycetes and fungi with elevated CO2 and mitigation of this
effect on actinomycetes with N amendments suggests that elevated CO2 and predicted
N limitation may alter the fate of slow‐turnover soil organic matter (SOM) in two
competing ways. Investigations need to focus on how these microorganisms may increase
slow‐turnover substrate use while possibly enhancing the prevalence of microbial cell
wall structures that can serve as precursors of stabilized SOM.
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Date
2011-02
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American Geophysical Union
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Citation
Ziegler, S. E., and S. A. Billings (2011), Soil nitrogen status as a regulator of carbon substrate flows through microbial
communities with elevated CO2, J. Geophys. Res., 116, G01011, http://dx.doi.org/10.1029/2010JG001434.