Thesis (M.D.)--University of Pennsylvania, 1802. / Microform version available in the Readex Early American Imprints series.

Thesis(M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

Invasive species introductions, namely the chestnut blight fungus (Cryphonectria parasitica) and hemlock woolly adelgid (Adelges tsugae), have permanently altered the overstory canopy of Appalachian forests by causing the dramatic die-offs of two ecologically significant tree species, American chestnut (Castanea dentata) and eastern hemlock (Tsuga canadensis). These canopy dominants once had significant roles in regulating understory communities. The loss of these trees, along with fire suppression, has driven two common evergreen shrubs, rosebay rhododendron (Rhododendron maximum) and mountain laurel (Kalmia latifolia), to expand and proliferate in areas where they were once restricted. These two common shrubs are recognized agents of change in Appalachian forests because of their abilities to modify soil seed banks, regulate light, and alter the local soil chemistry. This study documented evergreen shrub expansion across the Coweeta Creek basin over the past 36 years analyzing changes in winter greenness using harmonized multi-decadal archives of Landsat imagery. We found the greatest change in winter greenness in relatively dry areas: higher elevations (1275–1300 m), steeper slopes (33°–35°), southward aspects, and far from streams (600–800 m). Historical field data collected in three unmanaged watersheds at Coweeta showed a simultaneous decrease in T. canadensis and increase in R. maximum. We also documented the decline of a xerophytic canopy tree species, pitch pine (Pinus rigida), and an associate understory shrub, K. latifolia. Our analysis of the influence of terrain variables on evergreen shrub expansion allowed us to determine which of the two species was expanding in various locations with reasonable certainty. This study provides spatially explicit data on the expansion of two evergreen shrub species at the Coweeta Hydrologic Laboratory that could be used to pinpoint areas for future management interventions. / Master of Science / Forests in the eastern United States have changed substantially in response to the introduction of highly competitive invasive species. Some overstory tree species have been virtually eliminated from their functional role in regulating understory vegetation in many southern Appalachian ecosystems. Die-offs of these trees have allowed understory evergreen shrubs to expand into areas where they were once restricted. Shrubs that have expanded in response to overstory tree die-offs can alter the ecology of forests for the foreseeable future. Our work leveraged multi-decadal archives of wintertime satellite imagery to document the spread of understory evergreen shrubs in a watershed located in western North Carolina. We investigated the relationship of this spread to local environmental characteristics like elevation, steepness (slope), slope direction (north, south, east, west), and distance-from-stream. The greatest changes in evergreen vegetation were documented on terrain at relatively high elevations, locations farther from streams, on southerly aspects, and on relatively steep terrain. We included historical field data collected during the same time period that showed a simultaneous increase in two understory evergreen shrub species after the die-off of ecologically significant overstory tree species. This information will help forest managers by describing areas where substantial spread has occurred and potentially use this information to inform future management action.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Includes bibliographical references.

Mountain laurel (Kalmia latifolia L.) is relatively difficult to establish in landscapes. One experiment tested the effect of container size on the water relations of pinebark substrate embedded in field soil. Two other experiments tested the effects of transplant season and container size on landscape establishment of nursery-produced mountain laurel. Experiment one compared volumetric water content of embedded substrate of five sizes (4-L to 100-L) to adjacent field soil at two depths with time domain reflectometry (TDR) during a dry down cycle. Available water was calculated by subtracting unavailable water (estimated with pressure plates) from volumetric water content (TDR measurements). Adjacent soil contained more available water than embedded substrate. The middle depth held more water than the top. Larger pinebark substrate volumes retained higher volumetric water content than smaller volumes. The second experiment consisted of 7.6- and 19-L containers of Kalmia latifolia L. ‘Olympic Wedding’, transplanted into field soil in October or May. Larger container plants generally had lower xylem potential than smaller plants, but better visual ratings. Root growth into surrounding soil was negligible for all treatments. Leaf area was higher for spring transplants than fall transplants. Experiment three was a rhizotron study with 19-L plants, transplanted in October or May. Canopy growth of spring transplants was greater than fall transplants, but fall transplants had longer roots into the backfill. Overall, our data suggest that fall transplanting will potentially allow faster plant establishment than spring transplanting. The effect of container size on plant establishment could not be determined. / Master of Science