Plant carbon allocation drives turnover of old soil organic matter in permafrost tundra soils

Street, L. E., Garnett, M. H. , Subke, J.-A., Baxter, R., Dean, J. F. and Wookey, P. A. (2020) Plant carbon allocation drives turnover of old soil organic matter in permafrost tundra soils. Global Change Biology, 26(8), pp. 4559-4571. (doi: 10.1111/gcb.15134)

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Carbon cycle feedbacks from permafrost ecosystems are expected to accelerate global climate change. Shifts in vegetation productivity and composition in permafrost regions could influence soil organic carbon (SOC) turnover rates via rhizosphere (root zone) priming effects (RPEs), but these processes are not currently accounted for in model predictions. We use a radiocarbon (bomb‐14C) approach to test for RPEs in two Arctic tall shrubs, alder (Alnus viridis (Chaix) DC.) and birch (Betula glandulosa Michx.), and in ericaceous heath tundra vegetation. We compare surface CO2 efflux rates and 14C content between intact vegetation and plots in which below‐ground allocation of recent photosynthate was prevented by trenching and removal of above‐ground biomass. We show, for the first time, that recent photosynthate drives mineralization of older (>50 years old) SOC under birch shrubs and ericaceous heath tundra. By contrast, we find no evidence of RPEs in soils under alder. This is the first direct evidence from permafrost systems that vegetation influences SOC turnover through below‐ground C allocation. The vulnerability of SOC to decomposition in permafrost systems may therefore be directly linked to vegetation change, such that expansion of birch shrubs across the Arctic could increase decomposition of older SOC. Our results suggest that carbon cycle models that do not include RPEs risk underestimating the carbon cycle feedbacks associated with changing conditions in tundra regions.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Garnett, Dr Mark
Authors: Street, L. E., Garnett, M. H., Subke, J.-A., Baxter, R., Dean, J. F., and Wookey, P. A.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Global Change Biology
ISSN (Online):1365-2486
Published Online:17 June 2020
Copyright Holders:Copyright © 2020 The Authors
First Published:First published in Global Change Biology 26(8):4559-4571
Publisher Policy:Reproduced under a Creative Commons licence

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