Effects of soil organic matter properties and microbial community composition on enzyme activities in cryoturbated arctic soils

Schnecker, Jörg and Wild, Birgit and Hofhansl, Florian and Alves, Ricardo J Eloy and Bárta, Jiři and Čapek, Petr and Fuchslueger, Lucia and Gentsch, Norman and Gittel, Antje and Guggenberger, Georg and Hofer, Angelika and Kienzl, Sandra and Knoltsch, Anna and Lashchinskiy, Nikolay and Mikutta, Robert and Šantrůčková, Hana and Shibistova, Olga and Takriti, Mounir and Urich, Tim and Weltin, Georg and Richter, Andreas (2014) Effects of soil organic matter properties and microbial community composition on enzyme activities in cryoturbated arctic soils. PLoS ONE, 9 (4): e94076. ISSN 1932-6203

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Enzyme-mediated decomposition of soil organic matter (SOM) is controlled, amongst other factors, by organic matter properties and by the microbial decomposer community present. Since microbial community composition and SOM properties are often interrelated and both change with soil depth, the drivers of enzymatic decomposition are hard to dissect. We investigated soils from three regions in the Siberian Arctic, where carbon rich topsoil material has been incorporated into the subsoil (cryoturbation). We took advantage of this subduction to test if SOM properties shape microbial community composition, and to identify controls of both on enzyme activities. We found that microbial community composition (estimated by phospholipid fatty acid analysis), was similar in cryoturbated material and in surrounding subsoil, although carbon and nitrogen contents were similar in cryoturbated material and topsoils. This suggests that the microbial community in cryoturbated material was not well adapted to SOM properties. We also measured three potential enzyme activities (cellobiohydrolase, leucine-amino-peptidase and phenoloxidase) and used structural equation models (SEMs) to identify direct and indirect drivers of the three enzyme activities. The models included microbial community composition, carbon and nitrogen contents, clay content, water content, and pH. Models for regular horizons, excluding cryoturbated material, showed that all enzyme activities were mainly controlled by carbon or nitrogen. Microbial community composition had no effect. In contrast, models for cryoturbated material showed that enzyme activities were also related to microbial community composition. The additional control of microbial community composition could have restrained enzyme activities and furthermore decomposition in general. The functional decoupling of SOM properties and microbial community composition might thus be one of the reasons for low decomposition rates and the persistence of 400 Gt carbon stored in cryoturbated material.

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© 2014 Schnecker et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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17 May 2016 08:20
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31 Dec 2023 00:41