Abstract
The microbial metabolic quotient (MMQ), microbial respiration per unit of biomass, is a fundamental factor controlling heterotrophic respiration, the largest carbon flux in soils. The magnitude and controls of MMQ at regional scale remain uncertain. We compiled a comprehensive data set of MMQ to investigate the global patterns and controls of MMQ in top 30 cm soils. Published MMQ values, generally measured in laboratory microcosms, were adjusted on ambient soil temperature using long-term (30 yr) average site soil temperature and a Q10 = 2. The area-weighted global average of MMQ_Soil is estimated as 1.8 (1.5–2.2) (95% confidence interval) μmol C·h−1·mmol−1 microbial biomass carbon (MBC) with substantial variations across biomes and between cropland and natural ecosystems. Variation was most closely associated with biological factors, followed by edaphic and meteorological parameters. MMQ_Soil was greatest in sandy clay and sandy clay loam and showed a pH maximum of 6.7 ± 0.1 (mean ± se). At large scale, MMQ_Soil varied with latitude and mean annual temperature (MAT), and was negatively correlated with microbial N:P ratio, supporting growth rate theory. These trends led to large differences in MMQ_Soil between natural ecosystems and cropland. When MMQ was adjusted to 11°C (MMQ_Ref), the global MAT in the top 30 cm of soils, the area-weighted global averages of MMQ_Ref was 1.5 (1.3–1.8) μmol C·mmol MBC−1·h−1. The values, trends, and controls of MMQ_Soil add to our understanding of soil microbial influences on soil carbon cycling and could be used to represent microbial activity in global carbon models.
| Original language | English |
|---|---|
| Pages (from-to) | 429-441 |
| Number of pages | 13 |
| Journal | Ecological Monographs |
| Volume | 87 |
| Issue number | 3 |
| DOIs | |
| State | Published - Aug 2017 |
Funding
Daryl Moorhead provided valuable comments on data analysis and result presentation. X. Xu and X. Song are grateful for financial and facility supports from San Diego State University and University of Texas at El Paso. Financial assistance was partially provided by the SPRUCE and NGEE Arctic projects, which are supported by the Office of Biological and Environmental Research in the Department of Energy Office of Science. This study was partially supported by the Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences. Contribution by P. E. Thornton is supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. C. Song is supported by the National Natural Science Foundation of China (41125001). This research was also supported by the European Research Council Synergy grant ERC-2013-SyG 675 610028 IMBALANCE-P. The authors declare no conflict of interest. X. Xu designed the research, X. Xu and X. Song carried out the data compilation; X. Xu, J. Schimel, X. Song, C. Song, G. Yu, I. Janssens, and P. Thornton interpreted the data, D. Tang and X. Zhang helped with the data extraction from spatial data sets; R. Sinsabaugh significantly contributed to the comparison with carbon use efficiency and writing; X. Xu wrote the paper with assistance from other coauthors.
Keywords
- basal respiration
- edaphic factor
- meteorology
- microbial metabolic quotient
- pH
- soil microbial biomass