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Drivers of the microbial metabolic quotient across global grasslands |
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| Authors: | A C Risch S Zimmermann M Schütz E T Borer A A D Broadbent M C Caldeira K F Davies N Eisenhauer A Eskelinen P A Fay F Hagedorn J M H Knops J J Lembrechts A S MacDougall R L McCulley B A Melbourne J L Moore S A Power E W Seabloom M L Silviera R Virtanen L Yahdjian R Ochoa-Hueso |
| Institution: | 1. Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland;2. Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, USA;3. Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK;4. Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Lisbon, Portugal;5. Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA;6. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany;7. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
Ecology and Genetics Unit, University of Oulu, Oulu, Finland Department of Physiological Diversity, Helmholtz Center for Environmental Research – UFZ, Leipzig, Germany;8. USDA ARS Grassland Soil and Water Research, Temple, Texas, USA;9. Department of Health and Environmental Sciences, Xián Jiaotong-Liverpool University, Suzhou, China;10. Plants and Ecosystems (PLECO), University of Antwerp, Antwerp, Belgium;11. Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada;12. Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky, USA;13. Arthur Rylah Institute for Environmental Research, Heidelberg, Victoria, Australia School of Biological Sciences, Monash University, Clayton, Victoria, Australia;14. Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia;15. Range Cattle Research and Education Center, University of Florida, Gainesville, Florida, USA;16. Ecology and Genetics Unit, University of Oulu, Oulu, Finland;17. Facultad de Agronomía, Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA), Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad de Buenos Aires, Buenos Aires, Argentina;18. Department of Biology, University of Cádiz, Puerto Real, Spain |
| Abstract: | AimThe microbial metabolic quotient (MMQ; mg CO2-C/mg MBC/h), defined as the amount of microbial CO2 respired (MR; mg CO2-C/kg soil/h) per unit of microbial biomass C (MBC; mg C/kg soil), is a key parameter for understanding the microbial regulation of the carbon (C) cycle, including soil C sequestration. Here, we experimentally tested hypotheses about the individual and interactive effects of multiple nutrient addition (nitrogen + phosphorus + potassium + micronutrients) and herbivore exclusion on MR, MBC and MMQ across 23 sites (five continents). Our sites encompassed a wide range of edaphoclimatic conditions; thus, we assessed which edaphoclimatic variables affected MMQ the most and how they interacted with our treatments.LocationAustralia, Asia, Europe, North/South America.Time period2015–2016.Major taxaSoil microbes.MethodsSoils were collected from plots with established experimental treatments. MR was assessed in a 5-week laboratory incubation without glucose addition, MBC via substrate-induced respiration. MMQ was calculated as MR/MBC and corrected for soil temperatures (MMQsoil). Using linear mixed effects models (LMMs) and structural equation models (SEMs), we analysed how edaphoclimatic characteristics and treatments interactively affected MMQsoil.ResultsMMQsoil was higher in locations with higher mean annual temperature, lower water holding capacity and lower soil organic C concentration, but did not respond to our treatments across sites as neither MR nor MBC changed. We attributed this relative homeostasis to our treatments to the modulating influence of edaphoclimatic variables. For example, herbivore exclusion, regardless of fertilization, led to greater MMQsoil only at sites with lower soil organic C (< 1.7%).Main conclusionsOur results pinpoint the main variables related to MMQsoil across grasslands and emphasize the importance of the local edaphoclimatic conditions in controlling the response of the C cycle to anthropogenic stressors. By testing hypotheses about MMQsoil across global edaphoclimatic gradients, this work also helps to align the conflicting results of prior studies. |
| Keywords: | anthropogenic management climate herbivore exclusion microbial biomass carbon microbial respiration nutrient addition Nutrient Network: A Global Research Cooperative (NutNet) soil properties |