Spartina alterniflora Biomass Allocation and Temperature: Implications for Salt Marsh Persistence with Sea-Level Rise
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To predict the impacts of climate change, a better understanding is needed of the foundation species that build and maintain biogenic ecosystems. Spartina alterniflora Loisel (smooth cordgrass) is the dominant salt marsh-building plant along the US Atlantic coast. It maintains salt marsh elevation relative to sea level by the accumulation of aboveground biomass, which promotes sediment deposition and belowground biomass, which accretes as peat. Peat accumulation is particularly important in elevation maintenance at high latitudes where sediment supply tends to be limited. Latitudinal variation in S. alterniflora growth was quantified in eight salt marshes from Massachusetts to South Carolina. The hypothesis that allocation to aboveground and belowground biomass is phenotypically plastic was tested with transplant experiments among a subset of salt marshes along this gradient. Reciprocal transplants revealed that northern S. alterniflora decreased allocation to belowground biomass when grown in the south. Some northern plants also died when moved south, suggesting that northern S. alterniflora may be stressed by future warming. Southern plants that were moved north showed phenotypic plasticity in biomass allocation, but no mortality. Belowground biomass also decomposed more quickly in southern marshes. Our results suggest that warming will lead northern S. alterniflora to decrease belowground allocation and that belowground biomass will decompose more quickly, thus decreasing peat accumulation. Gradual temperature increases may allow for adaptation and acclimation, but our results suggest that warming will lower the ability of salt marshes to withstand sea-level rise.
KeywordsSpartina alterniflora Salt marsh Smooth cordgrass Climate change Biomass Elevation
We thank M. Cockrell, A. Crosby, S. Ergun, J. Gallagher, K. Gedan, M. Ivens, D. Johnson, H. Nelson, D. Seliskar, L. Szathmary, G. Watson, and P. Williams for their invaluable assistance in the lab and field. C. Roman and D. Sax are thanked for their thoughtful comments on the manuscript. This research (or a portion thereof) was conducted in the National Estuarine Research Reserve System under an award from the Estuarine Reserves Division, Office of Ocean and Coastal Resource Management, National Ocean Service, and National Oceanic and Atmospheric Administration. Additional funding was provided to SCC by the National Park Service George Melendez Wright Climate Change Fellowship, an award to HML from the ADVANCE Program of Brown University (National Science Foundation Grant no. 0548311), and awards to LAD from the National Science Foundation (DEB-1354494, OCE-1238212) and the Northeast Climate Science Center (DOI-G12AC00001, DOI-G13AC00410).
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Conflict of Interest
The authors declare that they have no conflict of interest.
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