Identification of Thermally Homogeneous Subunits in a Steep Appalachian Pasture

Abstract

Pasture improvement in the central Appalachian region is facilitated by knowledge of spatial relationships in microclimate attributable to complex topography. A small, steep horseshoe-shaped pasture watershed, with aspects encompassing 210°, in southern West Virginia was instrumented to measure microclimatic variability under low-maintenance pasture conditions and to identify thermally homogeneous subunits. Temperature measurements were made at 32 sites on a 30-m grid in the 3-ha pasture. Average two-week temperatures were measured using chemical temperature integrators located 35 cm above the ground and at 25- and 35-cm soil depths. Temperatures were measured during the growing seasons (May?September) of 1985 through 1988. Principal components analyses (PCA) were performed on the combined growing season data as well as on each year individually. The first two components delineated homogeneous areas related to topographic-induced conditions and soil water status. Topographic-induced conditions were not of the same importance from year to year. The PCA results were confirmed through the analysis of variance, which identified statistically significant similarities in group means. The identification of thermally homogeneous subunits in pasture provides useful information for making pasture management decisions that maximize forage production and conserve the soil resource.