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25 Years of Vegetation Change on Santa Rosa Island
Human land use of Santa Rosa Island dates back 13,000 years, starting with the island Chumash before ranching was introduced in 1843. Non-native ungulate populations were present on the island for over a 150 years. Intensive grazing led to replacement of native woodland, chaparral, and scrub vegetation with European grassland and vegetation patchiness. Following creation of Channel Islands National Park in 1986, all non-native grazers were targeted for removal to restore native vegetation on the island. The removal of non-native species from an ecosystem can be critical for the recovery process of native vegetation. By examining multiple data sources we were able to generalize land use management with respect to cattle accessibility on Santa Rosa Island. Vegetation classification as well as a terrain investigation was conducted on two remotely sensed images via GIS. Image one was created using a Landsat 7 image and regions of interest (ROIs) in order to delineate vegetation classes. Image two was modified from a Landsat 7 image to have the same classifications as image one. The terrain analysis completed on both images examined slope, aspect, concave, and convex curvatures in order to estimate cattle accessibility with respect to vegetation change. By analyzing these factors and their synergistic affects informed us about general rules associated with accessibility and change in vegetation. Accessibility as well as abiotic factors played a role in determining the land management practices as well as the degree of vegetation change from 1991 to 2015.
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