Abstract
Soil microbial carbon use efficiency (CUE), defined as the ratio between carbon (C) allocated to growth and C taken up by microorganisms, is pivotal for the understanding of C cycling in terrestrial ecosystems. Soil microbial CUE is thought to increase under nitrogen (N) addition, thereby mediating the effects of atmospheric N deposition on C cycling in soils. We studied the effects of N, phosphorus (P), and combined N and P addition on soil microbial CUE from a total of six grassland soils from South Africa, USA, and UK. Microbial CUE varied between 25 and 57% with a mean value of 40% across all sites, depth increments, and treatments. Most of the site variability in microbial CUE was explained by sand content, mean annual precipitation and temperature, and the dissolved organic C:dissolved N ratio. Soil microbial CUE as well as microbial biomass turnover time were robust to changes in N, P, and NP supply. However, N addition significantly reduced microbial respiration and C uptake in the topsoil. Taken together, N, P, and NP addition did not influence microbial CUE and biomass turnover time in grassland soils on different continents, indicating that microbial CUE varies little despite large changes in element inputs. Consequently, increased N inputs to soil may have a smaller impact on microbial CUE and biomass turnover time, and therefore C cycling in grassland soils, than expected and models assuming increased CUE with increasing N inputs could overestimate future C storage.
| Original language | English (US) |
|---|---|
| Article number | 107815 |
| Journal | Soil Biology and Biochemistry |
| Volume | 146 |
| DOIs | |
| State | Published - Jul 2020 |
Bibliographical note
Funding Information:M. Spohn thanks the German Research Foundation for funding this study through the Emmy Noether-program (grant SP1389/6-1 ). Coordination and data management of the Nutrient Network have been supported by funding to E. Borer and E. Seabloom from the National Science Foundation Research Coordination Network ( NSF-DEB-1042132 ) and Long Term Ecological Research ( DEB-1234162 and DEB-1831944 to Cedar Creek LTER) programs, and the Institute on the Environment (DG-0001-13). We thank Giovanni Pastore for his helpful comments on a previous version of the manuscript. We thank Renate Krauss, Uwe Hell, and Karin Söllner for technical assistance and thank the chemical analytics of the Bayreuth Center of Ecological and Environmental Research for performing parts of the chemical analyses and the Centre for Stable Isotope Research and Analysis of the University of Göttingen for measuring 18 O isotopes.
Funding Information:
M. Spohn thanks the German Research Foundation for funding this study through the Emmy Noether-program (grant SP1389/6-1). Coordination and data management of the Nutrient Network have been supported by funding to E. Borer and E. Seabloom from the National Science Foundation Research Coordination Network (NSF-DEB-1042132) and Long Term Ecological Research (DEB-1234162 and DEB-1831944 to Cedar Creek LTER) programs, and the Institute on the Environment (DG-0001-13). We thank Giovanni Pastore for his helpful comments on a previous version of the manuscript. We thank Renate Krauss, Uwe Hell, and Karin S?llner for technical assistance and thank the chemical analytics of the Bayreuth Center of Ecological and Environmental Research for performing parts of the chemical analyses and the Centre for Stable Isotope Research and Analysis of the University of G?ttingen for measuring 18O isotopes.
Publisher Copyright:
© 2020 Elsevier Ltd
Keywords
- Carbon mineralization
- Microbial growth
- Microbial growth efficiency
- Microbial respiration
- Nutrient fertilization
- Nutrient network (NutNet)
