Decadal-Scale Vegetation Change Driven by Salinity at Leading Edge of Rising Sea Level
As sea levels rise, low-lying coastal forests increasingly are subject to stressors such as inundation and saltwater exposure. At long timescales (for example, centuries), the extent of inundation and saltwater exposure will increase; however, on a decadal timescale, the role of these drivers may differ in both magnitude and direction. To investigate the drivers of decadal-scale vegetation change, we measured the changes in five metrics of vegetation composition and structure between 2003/2004 and 2016/2017 at 98 plots distributed across a vegetation gradient from coastal forest to brackish marshes (< 0.5–18 ppt). We used elevation as a proxy of inundation vulnerability and soil sodium concentration as a proxy of saltwater exposure, and we investigated relationships between these two variables and the change in vegetation conditions between the two sampling periods. Soil sodium concentration was a significant predictor of vegetation change for all five vegetation metrics, whereas the effect of elevation was not significant for any of the metrics. The one site that was affected by wildfire twice during the duration of the study shifted almost completely from forest to marsh with limited regeneration of woody vegetation observed in 2016/2017. Our results show that salinization in our system is a more important driver of vegetation change than inundation potential. Furthermore, the effects of drought-induced salinization could be amplified by the elevated risk of wildfire during droughts. Forecasting the response of coastal wetlands to rising sea levels will require a better understanding of the individual and combined effects of salinity, droughts, and wildfires on vegetation.
Keywordscoastal forest drought inundation marsh migration salinization wildfire
We thank the College of Natural Resources at North Carolina State University (Grant No. 769393) and the Department of the Interior Southeast Climate Adaptation Science Center for financial support. The biologists and managers of Alligator National Wildlife Refuge, Swanquarter National Wildlife Refuge, Gull Rock State Game Land, Alligator State Game Land, and Palmetto-Peartree Preserve assisted with access, logistical support, and local expertise and were invaluable to our study. We thank C. Bland, A. Bledsoe, L. Bobay, and L. Smart for their diligence and focus during collection of field data.
Data Accessibility Statement
The data reported in this study are permanently archived at the Pangaea Online Data Repository and can be found at https://doi.pangaea.de/10.1594/PANGAEA.896941.
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