Sea level rise (SLR) is causing vegetation regime shifts on both the seaward and landward sides of many coastal ecosystems, with the Eastern coast of North America experiencing accelerated impacts due to land subsidence and the weakening of the Gulf Stream. Tidal wetland ecosystems, known for their significant carbon storage capacity, are crucial but vulnerable blue carbon habitats. Recent observations suggest that in many coastal regions, SLR scenarios may exceed the threshold for elevation gain primarily through vertical accretion. Therefore, research has focused on mapping the landward expansion of marshes, as it is a vital process for estimating future wetland resilience to accelerated SLR. However, our understanding of coastal vegetation characteristics and dynamics in response to SLR is limited due to a lack of in-situ data and effective mapping strategies for delineating the boundaries, or ‘ecotones’, of these complex coastal ecosystems. In order to effectively study these transitioning ecosystems, it is necessary to employ reliable and scalable metrics that can differentiate between marsh and coastal forests. As such, integrating vegetation structure metrics from Light detection and ranging (Lidar) could enhance traditional mapping strategies compared to using optical data alone. Here, we characterized 3 coastal upland forests using terrestrial laser scanning (TLS) along a narrow elevation gradient in the Delaware Bay estuary that is particularly vulnerable to SLR. We analyzed the structural dynamics across forest edge-to-interior transects and utilized the comprehensive 3D data obtained from TLS to determine how elevation (i.e., inundation proxy) influenced the vertical stratification and other forest structural characteristics that may be consistently impacted by inundation at low lying elevations. Our findings revealed a consistent pattern between elevation and the Plant Area Index (PAI), a metric that holds potential for enhancing the delineation of complex coastal ecosystem boundaries, particularly in relation to landward marsh migration.

Primary Presenter: Elisabeth Powell, University of Maryland (epowell1@terpmail.umd.edu)

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