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Title: Stoichiometry of microbial carbon use efficiency in soils

The carbon use efficiency (CUE) of microbial communities partitions the flow of C from primary producers to the atmosphere, decomposer food webs, and soil C stores. CUE, usually defined as the ratio of growth to assimilation, is a critical parameter in ecosystem models, but is seldom measured directly in soils because of the methodological difficulty of measuring in situ rates of microbial growth and respiration. Alternatively, CUE can be estimated indirectly from the elemental stoichiometry of organic matter and microbial biomass, and the ratios of C to nutrient-acquiring ecoenzymatic activities. In this paper, we used this approach to estimate and compare microbial CUE in >2000 soils from a broad range of ecosystems. Mean CUE based on C:N stoichiometry was 0.269 ± 0.110 (mean ± SD). A parallel calculation based on C:P stoichiometry yielded a mean CUE estimate of 0.252 ± 0.125. The mean values and frequency distributions were similar to those from aquatic ecosystems, also calculated from stoichiometric models, and to those calculated from direct measurements of bacterial and fungal growth and respiration. CUE was directly related to microbial biomass C with a scaling exponent of 0.304 (95% CI 0.237–0.371) and inversely related to microbial biomass P with a scalingmore » exponent of -0.234 (95% CI -0.289 to -0.179). Relative to CUE, biomass specific turnover time increased with a scaling exponent of 0.509 (95% CI 0.467–0.551). CUE increased weakly with mean annual temperature. CUE declined with increasing soil pH reaching a minimum at pH 7.0, then increased again as soil pH approached 9.0, a pattern consistent with pH trends in the ratio of fungal : bacteria abundance and growth. Structural equation models that related geographic variables to CUE component variables showed the strongest connections for paths linking latitude and pH to β-glucosidase activity and soil C:N:P ratios. Finally, the integration of stoichiometric and metabolic models provides a quantitative description of the functional organization of soil microbial communities that can improve the representation of CUE in microbial process and ecosystem simulation models.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8]
  1. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Biology
  2. Smithsonian Tropical Research Inst., Balboa (Panama)
  3. Boston Univ., MA (United States). Dept. of Biology
  4. Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Ecology, Evolution, and Behavior
  5. Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Ecology, Evolution, and Behavior. Dept. of Plant Biology
  6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  7. Univ. of Toledo, OH (United States). Dept. of Environmental Sciences
  8. Univ. of Utah, Salt Lake City, UT (United States). Environmental and Sustainable Studies Program
Publication Date:
Report Number(s):
Journal ID: ISSN 0012-9615
Grant/Contract Number:
AC52-06NA25396; DEB-1053237
Accepted Manuscript
Journal Name:
Ecological Monographs
Additional Journal Information:
Journal Volume: 86; Journal Issue: 2; Journal ID: ISSN 0012-9615
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Minnesota, Minneapolis, MN (United States); Univ. of New Mexico, Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF)
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; 54 ENVIRONMENTAL SCIENCES; biomass turnover; carbon use efficiency; ecoenzymatic activity; ecological stoichiometry; microbial communities; soil ecology; nutrient use efficiency
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1401670