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GCE IV - Key Finding in 2020

    Patterns of marsh change at three LTER sites

    The vegetated area of a salt marsh can shift over time as the result of advance and retreat of the marsh edge, but it can also change due to channel widening and contraction, formation and drainage of ponds, interior mud flat formation and revegetation, and migration of the marsh onto the upland (Fig. 1). Understanding patterns of vegetation loss and gain can provide insight into what factors are important in controlling marsh dynamics, as each of these shifts responds to different processes. As part of a cross-site coastal SEES project that leveraged LTER data, Burns et al. (2020 a) used historical aerial photos to measure changes in marsh features over approximately 70 years at study areas located in the GCE domain as well as the Virginia Coast Reserve (VCR) and Plum Island Ecosystems (PIE) LTER sites. The net change was neutral at the GCE site, as losses, which were primarily due to channel widening, were largely offset by channel contraction in other areas (Table 1). The study marsh at VCR increased over time due to migration onto the upland, despite the fact that low-lying areas experienced extensive loss as the result of interior mud flat expansion. In contrast, vegetated marsh area at PIE decreased over time due to losses from ponding, channel widening, and erosion at the open fetch marsh edge. In a companion study, Burns et al. (2020 b) focused specifically on the marsh edges of each site and again found differences in the open fetch edge that were offset in part by changes in the interior channels. This demonstrates the importance of assessing shoreline changes throughout the marsh, as rates of retreat and advance at the open-fetch marsh perimeter may not be indicative of the overall change. These studies offer a reminder that marshes are dynamic environments and that multiple processes are occurring simultaneously that affect the extent of vegetated marsh habitat. Understanding what factors are important in driving losses and gains provides a useful context for identifying site-specific management options.



LTER
NSF

This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.