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A landscape-scale assessment of above- and belowground primary production in coastal wetlands: Implications for climate change-induced community shifts

Camille L. Stagg·Donald R. Schoolmaster·Sarai C. Piazza·Gregg Snedden·Gregory D. Steyer·Craig J Fischenich·Robert W. McComas
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Abstract

Above- and belowground production in coastal wetlands are important contributors to carbon accumulation and ecosystem sustainability. As sea level rises, we can expect shifts to more salt-tolerant communities, which may alter these ecosystem functions and services. Although the direct influence of salinity on species-level primary production has been documented, we lack an understanding of the landscape-level response of coastal wetlands to increasing salinity. What are the indirect effects of sea-level rise, i.e., how does primary production vary across a landscape gradient of increasing salinity that incorporates changes in wetland type? This is the first study to measure both above- and belowground production in four wetland types that span an entire coastal gradient from fresh to saline wetlands. We hypothesized that increasing salinity would limit rates of primary production, and saline marshes would have lower rates of above- and belowground production than fresher marshes. However, along the Northern Gulf of Mexico Coast in Louisiana, USA, we found that aboveground production was highest in brackish marshes, compared with fresh, intermediate, and saline marshes, and belowground production was similar among all wetland types along the salinity gradient. Multiple regression analysis indicated that salinity was the only significant predictor of production, and its influence was dependent upon wetland type. We concluded that (1) salinity had a negative effect on production within wetland type, and this relationship was strongest in the fresh marsh (0–2 PSU) and (2) along the overall landscape gradient, production was maintained by mechanisms at the scale of wetland type, which were likely related to plant energetics. Regardless of wetland type, we found that belowground production was significantly greater than aboveground production. Additionally, inter-annual variation, associated with severe drought conditions, was observed exclusively for belowground production, which may be a more sensitive indicator of ecosystem health than aboveground production.

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Camille L. Stagg, Donald R. Schoolmaster, Sarai C. Piazza, Gregg Snedden, Gregory D. Steyer, Craig J Fischenich, Robert W. McComas. 2016-10-24. A landscape-scale assessment of above- and belowground primary production in coastal wetlands: Implications for climate change-induced community shifts. https://doi.org/10.1007/s12237-016-0177-y

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