SPATIAL ANALYSIS OF GHOST FOREST SOIL CHARACTERISTICS ON ASSATEAGUE ISLAND, VA: INVESTIGATING COASTAL PROCESSES AND MARITIME FOREST LOSS ON BARRIER ISLANDS

Maritime forests provide numerous benefits to barrier islands which include increasing the overall stability, decreasing the rate of erosion, and the protection of other plants and animals. Previous studies have documented an overall loss of Loblolly Pine (Pinus taeda) forests throughout the mid-Atlantic. This decrease is tentatively linked to the intrusion of salt water into coastal aquifers by means of storm surge, extensive groundwater pumping, subsidence, drought, and sea level rise. The purpose of this study was to measure and spatially analyze the possible correlations between lateral variations of soil parameters (pH, electrical conductivity, organic matter, and grain size) and tree health on Assateague Island, Virginia. This study analyzed 98 total soil samples from two different geographic sites (ocean side and sound side). Tree health scores for a total of 436 Loblolly Pines were collected from both locations. A GIS was used to perform a spatial analysis to determine spatial variation of each parameter at each site relative to tree health scores. Results indicate that soil pH and electrical conductivity are lower (pH 5.2-5.8) near healthy, unimpaired trees and at higher elevations. Impaired trees (i.e. already dead and dying) are generally located at the margins of the forest stands and at lower elevations where pH ranges 6.0 to 6.8. Lower elevations and high organic content was characteristic of the sound side site while, higher elevations of about three meters above sea level and soil organics were found to be lower ocean side. Increased development of ghost forests is more abundant on the sound side site where lower elevations and a higher average pH (6.14) occur. These data do not provide us with specific evidence of sea level rise, but the death of 100+ year old trees indicates that tree death is likely not tied to single episodes of overwash or seasonal changes in aquifer parameters. Data suggests that pH change to more alkaline conditions more similar to that of sea-water and less like that of freshwater, may be tied to the development of ghost forest. By documenting the relationships between soil parameters and tree health, a more complete understanding of the early impacts and signs of a changing coastal environment can be gained.