Stimulation of r- vs. K-selected microorganisms by elevated atmospheric CO2 depends on soil aggregate size |
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Authors: | Maxim Dorodnikov Evgenia Blagodatskaya Sergey Blagodatsky reas Fangmeier & Yakov Kuzyakov |
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Institution: | Department of Agroecosystem Research, University of Bayreuth, Bayreuth, Germany;;Institute of Landscape and Plant Ecology (320), University of Hohenheim, Stuttgart, Germany;and;Institute of Physico-Chemical and Biological Problems in Soil Science, RAS, Puschino, Russia |
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Abstract: | Increased root exudation under elevated atmospheric CO2 and the contrasting environments in soil macro- and microaggregates could affect microbial growth strategies. We investigated the effect of elevated CO2 on the contribution of fast- ( r -strategists) and slow-growing ( K -strategists) microorganisms in soil macro- and microaggregates. We fractionated the bulk soil from the ambient and elevated (for 5 years) CO2 treatments of FACE-Hohenheim (Stuttgart) into large macro- (>2 mm), small macro- (0.25–2.00 mm), and microaggregates (<0.25 mm) using 'optimal moist' sieving. Microbial biomass (Cmic), the maximum specific growth rate (μ), growing microbial biomass (GMB) and lag-period ( t lag) were estimated by the kinetics of CO2 emission from bulk soil and aggregates amended with glucose and nutrients. Although Corg and Cmic were unaffected by elevated CO2, μ values were significantly higher under elevated than ambient CO2 for bulk soil, small macroaggregates, and microaggregates. Substrate-induced respiratory response increased with decreasing aggregate size under both CO2 treatments. Based on changes in μ, GMB and lag period, we conclude that elevated atmospheric CO2 stimulated the r- selected microorganisms, especially in soil microaggregates. Such an increase in r -selected microorganisms indicates acceleration of available C mineralization in soil, which may counterbalance the additional C input by roots in soils in a future elevated atmospheric CO2 environment. |
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Keywords: | FACE microaggregates macroaggregates SIGR microbial growth strategies |
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