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Marine Ecology Progress Series

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MEPS 537:9-21 (2015)  -  DOI:

Ecosystem engineering by large grazers enhances carbon stocks in a tidal salt marsh

Kelly Elschot1,*, Jan P. Bakker1, Stijn Temmerman2, Johan van de Koppel3, Tjeerd J. Bouma3

1Community and Conservation Ecology Group, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands
2Ecosystem Management Research Group, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
3Spatial Ecology Group, Royal Netherlands Institute for Sea Research (NIOZ-Yerseke), PO Box 140, 4400 AC Yerseke, The Netherlands
*Corresponding author:

ABSTRACT: Grazers can have a large impact on ecosystem processes and are known to change vegetation composition. However, knowledge of how the long-term presence of grazers affects soil carbon sequestration is limited. In this study, we estimated total accumulated organic carbon in soils of a back-barrier salt marsh and determined how this is affected by long-term grazing by both small and large grazers in relation to age of the ecosystem. In young marshes, where small grazers predominate, hare and geese have a limited effect on total accumulated organic carbon. In older, mature marshes, where large grazers predominate, cattle substantially enhanced carbon content in the marsh soil. We ascribe this to a shift in biomass distribution in the local vegetation towards the roots in combination with trampling effects on the soil chemistry. These large grazers thus act as ecosystem engineers: their known effect on soil compaction (based on a previous study) enhances anoxic conditions in the marsh soil, thereby reducing the oxygen available for organic carbon decomposition by the local microbial community. This study showed that the indirect effects of grazing can significantly enhance soil carbon storage through changing soil abiotic conditions. This process should be taken into account when estimating the role of ecosystems in reducing carbon dioxide concentration in the atmosphere. Ultimately, we propose a testable conceptual framework that includes 3 pathways by which grazers can alter carbon storage: (1) through above-ground biomass removal, (2) through alteration of biomass distribution towards the roots and/or (3) by changing soil abiotic conditions that affect decomposition.

KEY WORDS: Carbon sequestration · Climate change · Coastal wetland · Grazing · Redox potential · Soil compaction · Succession

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Cite this article as: Elschot K, Bakker JP, Temmerman S, van de Koppel J, Bouma TJ (2015) Ecosystem engineering by large grazers enhances carbon stocks in a tidal salt marsh. Mar Ecol Prog Ser 537:9-21.

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