Soil respiration is not limited by reductions in microbial biomass during long-term soil incubations |
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| Institution: | 1. Natural Resources Ecology Laboratory, Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO 80523-1499, USA;2. Soil Plant Nutrient Research, U.S. Department of Agriculture-ARS, 2150 Centre Avenue, Building D, Suite 100, Fort Collins, CO 80526-8119, USA;3. Biology Department, Bradley University, 1501 W. Bradley Ave., Peoria, IL 61625, USA;4. Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI 48824, USA;1. Plant, Soil and Microbial Sciences, Michigan State University, Plant & Soil Sciences Building, 1066 Bogue St., East Lansing, MI 48824, USA;2. Department of Agronomy, University of Swabi, KP, Pakistan;1. Institute of Soil Science and Land Evaluation, Soil Biology Section, University of Hohenheim, Emil-Wolff-Str. 27, 70593 Stuttgart, Germany;2. Institute of Soil Science and Land Evaluation, Biogeophysics Section, University of Hohenheim, Emil-Wolff-Str. 27, 70593 Stuttgart, Germany;3. Institute of Plant Production and Agroecology in the Tropics and Subtropics, University of Hohenheim, Garbenstr. 13, 70593 Stuttgart, Germany;4. Institute of Crop Science, University of Hohenheim, Fruwirthstr. 20, 70593 Stuttgart, Germany;5. Institute of Physics and Meteorology, University of Hohenheim, Garbenstrasse 30, 70593 Stuttgart, Germany;1. Institute of Soil Science and Land Evaluation, Soil Biology Department, University of Hohenheim, Emil-Wolff-Str. 27, 70599 Stuttgart, Germany;2. School of Environment and Natural Resources, The Ohio State University, 210 Kottman Hall, 2021 Coffey Rd., Columbus, OH 43210, United States;3. Institute of Soil Science and Land Evaluation, Biogeophysics Department, University of Hohenheim, Emil-Wolff-Str. 27, 70599 Stuttgart, Germany;4. Environmental Science Research Institute, Shahid Beheshti University, G.C., Tehran, Iran;5. Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Garbenstr. 13, 70599 Stuttgart, Germany;1. Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW 2751, Australia;2. The James Hutton Institute, Craigiebuckler, Aberdeen, Scotland, UK;3. Institute of Molecular, Cell and System Biology, University of Glasgow, Glasgow, Scotland, UK;4. Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark;5. Global Centre for Land-based Innovation, University of Western Sydney, Penrith, NSW 2751, Australia;1. Linze Inland River Basin Research Station, Key Laboratory of Ecohydrology of Inland River Basin, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Lehrstuhl für Bodenkunde, Department of Ecology and Ecosystem Management, Center of Life and Food Sciences, Weihenstephan, Technische Universität München, D-85350 Freising-Weihenstephan, Germany;2. TUM|Stat, Lehrstuhl für Mathematische Statistik, Technische Universität München, D-85748 Garching, Germany;3. Helmholtz Zentrum München, German Research Center for Environmental Health, Research Unit for Environmental Genomics, D-85764 Neuherberg, Germany;4. Institute for Advanced Study, Technische Universität München, Lichtenbergstraße 2a, D-85748 Garching, Germany |
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| Abstract: | Declining rates of soil respiration are reliably observed during long-term laboratory incubations. However, the cause of this decline is uncertain. We explored different controls on soil respiration to elucidate the drivers of respiration rate declines during long-term soil incubations. Following a long-term (707 day) incubation (30 °C) of soils from two sites (a cultivated and a forested plot at Kellogg Biological Station, Hickory Corners, MI, USA), soils were significantly depleted of both soil carbon and microbial biomass. To test the ability of these carbon- and biomass-depleted (“incubation-depleted”) soils to respire labile organic matter, we exposed soils to a second, 42 day incubation (30 °C) with and without an addition of plant residues. We controlled for soil carbon and microbial biomass depletion by incubating field fresh (“fresh”) soils with and without an amendment of wheat and corn residues. Although respiration was consistently higher in the fresh versus incubation-depleted soil (2 and 1.2 times higher in the fresh cultivated and fresh forested soil, respectively), the ability to respire substrate did not differ between the fresh and incubation-depleted soils. Further, at the completion of the 42 day incubation, levels of microbial biomass in the incubation-depleted soils remained unchanged, while levels of microbial biomass in the field-fresh soil declined to levels similar to that of the incubation-depleted soils. Extra-cellular enzyme pools in the incubation-depleted soils were sometimes slightly reduced and did not respond to addition of labile substrate and did not limit soil respiration. Our results support the idea that available soil organic matter, rather than a lack microbial biomass and extracellular enzymes, limits soil respiration over the course of long-term incubations. That decomposition of both wheat and corn straw residues did not change after major changes in the soil biomass during extended incubation supports the omission of biomass values from biogeochemical models. |
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| Keywords: | Soil organic matter (SOM) Respiration Microbial biomass Incubation Extracellular enzymes Substrate decomposition |
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