Graduate Thesis Or Dissertation
 

A Study of Vegetation Change Over Time in the Salt Marshes of the Salmon River Estuary, Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4x51hr56n

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  • The salt marshes of the Salmon River Estuary, Oregon have been of interest for decades due to their disturbance and restoration history, as well as the presence of long-term vegetation transects that were established as early as the 1970s. Vegetation abundance data have been gathered in the four sites of interest, Mitchell Marsh, Y Marsh, Salmon Creek Marsh, and the never-diked Reference Marsh, by various research teams for decades. These data have been used in studies to determine how individual marshes have changed over time or how the marshes compared to each other at a given point in time. However, this study seeks to analyze vegetation change over time in all of the marshes from 1988 to 2015. Historical vegetation data were compiled and analyzed by marsh and by year using multivariate statistical analyses, including Multi-response Permutation Procedure, Non-metric Multidimensional Scaling, and Indicator Species Analysis. The LandTrendr algorithm for Google Earth Engine was used to determine if changes in spatial patterns within the marshes can be detected using remote sensing data. Results indicate that there are significant differences between the vegetation composition of the restored marshes and the remnant marsh. Restored marshes have become more similar to one another over time but have not returned to their expected reference conditions in the time since restoration. LandTrendr results indicate that spatial changes in marsh vegetation vary within each marsh and between marshes. Visualization of the results show patterns in the marsh vegetation that were not necessarily detected in the analyses of the field vegetation data. The vegetation composition of the salt marshes of the Salmon River Estuary is influenced by restoration, and continued long-term monitoring of these ecosystems is an important aspect of their restoration projects. Future studies of these marshes should consider establishing new transects in under-measured areas within the marshes, such as the Reference Marsh and the low marsh zones, in order to better capture the spatial patterns of vegetation composition in the marshes.
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  • Pending Publication
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  • 2021-06-04 to 2023-07-05

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