Flooding alters plant-mediated carbon cycling independently of elevated atmospheric CO2 concentrations

Journal of Geophysical Research: Biogeosciences
By: , and 

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Abstract

Plant‐mediated processes determine carbon (C) cycling and storage in many ecosystems; how plant‐associated processes may be altered by climate‐induced changes in environmental drivers is therefore an essential question for understanding global C cycling. In this study, we hypothesize that environmental alterations associated with near‐term climate change can exert strong control on plant‐associated ecosystem C cycling and that investigations along an extended hydrologic gradient may give mechanistic insight into C cycling. We utilize a mesocosm approach to investigate the response of plant, soil, and gaseous C cycling to changing hydrologic regimes and elevated atmospheric carbon dioxide (CO2) concentrations expected by 2100 in a coastal salt marsh in Louisiana, USA. Although elevated CO2 had no significant effects on C cycling, we demonstrate that greater average flooding depth stimulated C exchange, with higher rates of labile C decomposition, plant CO2 assimilation, and soil C respiration. Greater average flooding depth also significantly decreased the soil C pool and marginally increased the aboveground biomass C pool, leading to net losses in total C stocks. Further, flooding depths along an extended hydrologic gradient garnered insight into decomposition mechanisms that was not apparent from other data. In C‐4 dominated salt marshes, sea‐level rise will likely overwhelm effects of elevated CO2 with climate change. Deeper flooding associated with sea‐level rise may decrease long‐term soil C pools and quicken C exchange between soil and atmosphere, thereby threatening net C storage in salt marsh habitats. Manipulative studies will be indispensable for understanding biogeochemical cycling under future conditions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Flooding alters plant-mediated carbon cycling independently of elevated atmospheric CO2 concentrations
Series title Journal of Geophysical Research: Biogeosciences
DOI 10.1029/2017JG004369
Volume 123
Issue 6
Year Published 2018
Language English
Publisher American Geophysical Union
Contributing office(s) Wetland and Aquatic Research Center
Description 12 p.
First page 1976
Last page 1987