Gradient analysis of secondary forests of eastern west virginia

Vegetation/environment relationships in two contiguous physiographic regions in eastern West Virginia were examined to determine local and sub-regional gradients underlying vegetation patterns. For 258 plots sampled in the Monongahela National Forest, West Virginia, broad vegetation patterns expressed along ordination axes were strongly related to elevation. Plots were ordered along the first ordination axis from high-elevation, mesic sites in the Allegheny Mountains to sandy, steep, lower-elevation sites in the Ridge and Valley. A comparison of mean soil-site factors between physiographic regions indicated that only depth of A horizon differed significantly. These similarities were reflected in the community types derived from TWINSPAN analysis. All seven community types were represented in both regions, although some regional affinity was apparent. Subsequent separate ordinations of plots within the Ridge and Valley and Allegheny Mountains showed community variation correlated with elevation. In the Ridge and Valley, geographic location, surface rock cover, topographic moisture and stand age were secondary gradients related to community distribution. In contrast, secondary gradients in the Allegheny Mountains included topographic moisture and solar radiation.