Chapter 5 Resources

Hydric Soils of Mid-Atlantic Freshwater Wetlands



The hydrogeomorphic (HGM) approach to wetland functional assessment has been derived as a tool to classify wetlands based on their landscape position, water source, and hydrologic activity. This classification provide a useful framework in which to study wetland functions and characteristics, thus allowing for a greater understanding of one of our valuable natural resources.Many important chemical transformations that distinguish wetlands from nonwetlands take place in wetland soils. A study of these soils in the context of HGM classification provides information on which to base future resource management decisions. Analyses were conducted to identify variation in soil characteristics across a gradient of seven HGM subclasses. Five soil characteristics were analyzed: 1) texture, 2) organic matter, 3) matrix chroma, 4) moisture/hydrologic condition, and 5) redoxymorphic features. A second analysis was performed to determine if soil properties varied significantly between relatively pristine/reference wetlands and degraded/non-reference wetlands. These hypotheses were tested on soils data collected mainly within the Ridge and Valley region of Pennsylvania; data were obtained from 141 reference standard wetlands sampled by the Penn State Cooperative Wetlands Center. Significant variation was identified in HGM subclasses along a hydrologic gradient. Low-energy, depression wetlands possessed distinctly different characteristics than high-energy, riverine wetlands. Slope wetlands typically displayed intermediate conditions between depression and riverine sites. The clearest trends identified were for organic matter content, chroma, and soil moisture. While variability existed between reference and non-reference sites, the differences were not significant enough to support the hypothesis. The results did, however, indicate a tendency for reference wetlands to possess a wider range of variation than more degraded wetlands for a given soil property. Loss of natural wetland variation may be related to increases in degradation; further work must be done to explore this finding.