Date

Summer 2020

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Applied Environmental Science

Abstract

Sea level rise threatens coastal wetlands worldwide. In response, wetland restoration projects are implementing strategies that decrease vulnerability to this threat. Vegetation monitoring at sites employing new restoration strategies, including determination of appropriate and efficient monitoring techniques, is critical to improve understanding of factors leading to restoration success and maximize benefits of future projects. In Central California, sediment addition raised a degraded marsh plain to a high elevation expected to be resilient to sea level rise over the next century. We conducted area searches of plant survival and modeled effects of nine predictors on new vegetation cover using two monitoring strategies: 1) transect surveys, and 2) unmanned aircraft systems (UAS) imagery. We conducted targeted sediment sampling to examine additional chemical or physical sediment properties contributing to vegetation patterns. Limited vegetation survived sediment addition, likely due to the thickness and placement method. Cover reached 8-14% in the initially-bare area after one year. Elevation and inundation frequency were particularly critical to understanding restoration success, with greatest cover in high-elevation areas tidally-inundated < 0.85% of the time. Sediment analysis suggested greater salinity stress and ammonia levels in poorly-vegetated compared to well-vegetated areas at the same elevation, which may be driven by variation in physical sediment properties. Similar modeling results indicate both transect and UAS methods were suitable for monitoring this site. Field transects may provide the best approach for tracking vegetation colonization if resources are limited, but UAS can complement this to provide landscape perspective.

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