DETERMINING RELATIVE ABUNDANCE OF CATSKILL REGION SOILS BASED ON GIS ANALYSIS OF NRCS SOIL SURVEY DATA

The Catskill High Peaks Ecoregion, as defined by the U.S. Geological Survey, is made up of portions of Ulster, Sullivan, Greene and Delaware Counties. The NRCS conducted soil surveys of these four counties, which were issued over a span of 27 years. Over that time period, the soil classification system and nomenclature has evolved resulting in discontinuities in soil mapping units across county boundaries. In addition, relative abundances of soil series are difficult to ascertain due to the practice of mapping soils as complexes containing two or more different soil series. The objective of this research project was to use GIS methods to determine the relative abundance of soil series, to adjust older mapping to reflect current nomenclature and to develop a more unified treatment of Catskill Region soils. The primary change in soil classification involves the addition of the soil temperature regime (mesic vs. frigid) as a criterion for classifying soils in the more recent soil surveys (Sullivan, Greene and Delaware) and the lack this criterion in the oldest soil survey (Ulster). In Ulster County, the dominant well-drained soils developed on glacial till parent material are assigned to the Arnot (shallow), Oquaqa (moderately deep) and Lackawana (deep, with fragipan) soil series without consideration for soil temperature regime. In the other Catskill Region counties, Arnot, Oquaga and Lackawana are mapped only at lower elevations, in the mesic soil temperature regime, and the frigid analogues of these soil series, Halcott, Vly and Lewbeach, are mapped at higher elevations starting at 1700 feet. GIS methods were used to calculate the areal extent of each soil series as originally mapped and after reassignment of Ulster County high elevation soils from Arnot/Oquaga/Lacakawana to Halcott/Vly/Lewbeach. After these adjustments, the geographic extent of the dominant well-drained soils developed on glacial till is as follows: Halcott at 91,000 acres, or 17.4% of study area, Vly at 84,000 acres, or 16% of study area, and Lewbeach at 61,000 acres, or 12% of the study area.