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Drivers of the microbial metabolic quotient across global grasslands
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Orientador(es)
Resumo(s)
Aim: The 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.
Location: Australia, Asia, Europe, North/South America.
Time period: 2015–2016.
Major taxa: Soil microbes.
Methods: Soils 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.
Results: MMQsoil 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 conclusions: Our 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.
Descrição
Palavras-chave
anthropogenic management climate herbivore exclusion microbial biomass carbon microbial respiration nutrient addition Nutrient Network: A Global Research Cooperative (NutNet) soil properties
Contexto Educativo
Citação
Risch, A. C., Zimmermann, S., Schütz, M., Borer, E. T., Broadbent, A. A. D., Caldeira, M. C., Davies, K. F., Eisenhauer, N., Eskelinen, A., Fay, P. A., Hagedorn, F., Knops, J. M. H., Lembrechts, J. J., MacDougall, A. S., McCulley, R. L., Melbourne, B. A., Moore, J. L., Power, S. A., Seabloom, E. W. … Ochoa-Hueso, R. (2023). Drivers of the microbial metabolic quotient across global grasslands. Global Ecology and Biogeography, 32, 904–918.
Editora
Wiley