Remotely Sensing Evergreen Shrub Expansion in the Southern Appalachians

Keywords: Remote Sensing, Rhododendron, Southern Appalachian
Session Type: Virtual Poster Abstract
Day: Sunday
Session Start / End Time: 2/27/2022 05:20 PM (Eastern Time (US & Canada)) - 2/27/2022 06:40 PM (Eastern Time (US & Canada))
Room: Virtual 32

Abstract

The introduction of invasive species has dramatically altered forests in the eastern United States over the last century. Die-offs of common overstory trees, especially eastern hemlock (Tsuga canadensis) and American chestnut (Castanea dentata), have allowed light to reach further into the canopies in many Appalachian forests. Previous studies have documented a relationship between this mass canopy disturbance and the proliferation of American rhododendron (Rhododendron maximum). Unchecked expansion of R. maximum in the Southern Appalachians often initiates environmental changes harmful to other species, such as dense shading that inhibits canopy tree recruitment, the modification of seed bank structures, and the alteration of riparian vegetation successional trends. This research documents the spatiotemporal patterns of R. maximum expansion in the Coweeta Creek watershed, Otto, North Carolina, across the past 34 years using contemporary remote sensing techniques. We compiled yearly wintertime composite Landsat 5 and Landsat 8 imagery from 1984–2021 to view understory evergreen vegetation. Ancillary terrain-data layers were generated to relate R. maximum to various basin characteristics including elevation, aspect, slope, distance-from-stream, and maximal curvature. Preliminary results show yearly winter greenness decreasing during the early portion of our study period, then increasing. This could be attributed to the die-off of T. canadensis from the introduction of hemlock wooly adelgid (Adelges tsugae), and subsequent release of R. maximum. This research evaluates R. maximum’s potential replacement of economically and ecologically significant overstory tree species and provides insights on some geomorphological drivers behind rhododendron expansion that may be useful to land managers.