Research Accomplishment Reports 2009

Hydropedology: Genesis, Properties, and Distribution of Hydromorphic Soils

A.D. Karathanasis
Department of Plant and Soil Sciences

 

Non-Technical Summary

Because of the environmental and economic importance of riverine resources as well as wetlands in the region, pedologists working together under NE-1021 have been developing expertise in the identification, characterization, classification, and land use interpretations for hydromorphic soils (soils that have formed in the presence of excess water) within these areas. The key linkage among these soils and resources across the landscape is the hydrology. Understanding the integrated effects of the hydrologically-driven processes associated with saturation, inundation, and transport across the landscape is critical for the development of numerous soil based land use interpretations. For example, understanding soil morphology/water table relationships is critical in developing interpretations for the construction of buildings and roads, surface application of waste, the use of on-site waste disposal systems, and the function of various wetlands in storing carbon (C) and providing beneficial ecological services. Wetland delineation is a multi-million dollar industry.

New techniques in landscape modeling are allowing investigators to identify wetlands using geospatial analysis and remote sensing (Pantaleoni et al., 2009a and 2009b). The improved mapping of wetlands is intended to improve the comprehensive National Wetland Inventory maps used as a basis for legislative decisions and wetland monitoring. Identification of hydric soils is essential in the on-site delineation process. Field indicators of hydric soils were developed to facilitate jurisdictional determinations of wetlands by identifying hydric soils (USDA-NRCS, 2006). Several field indicators rely on the quantity of soil C and may prove useful in predicting the amount of soil C in the surface of wetland soils. Some hydric soils, however, fail to develop the typical morphology found in most wetland soils. These so called "problem hydric soils" occur across the entire region and need to be addressed from a regional perspective (Vepraskas and Sprecher, 1997; Castenson, 2004; Zurheide, 2009).

Across the United States efforts have been ongoing to develop regional supplements to the ACOE Wetland Delineation Manual (Environmental Laboratory, 1987). These supplements would provide guidelines for identifying hydric soils using regional hydric soil indicators. Working within the proposed regional framework will allow for testing of hypotheses across climatic gradients, across parent material types (coastal plain, residual, and glacial), and among different types and settings of coastal, riverine, and subaqueous soils. Testing these hypotheses is not possible for a single investigator working within a single state and must be done at the regional level. Addressing these questions within a regional framework is also critical because the major agencies that use the soils information that pedologists collect, such as USDA-NRCS, USACOE, USEPA, all work in a region-wide context. Data gathered, relationships that are established, and interpretations that are made are therefore much more meaningful to the user if the science was tested within a region-wide context.

2009 Project Description

High-elevation Appalachian wetlands often support unique plant communities and rare species, yet the vegetation characteristics of mountain wetlands in Kentucky (USA) are poorly documented. At three relatively undisturbed, southeastern Kentucky sites, a quantitative vegetation survey was conducted to determine the community composition and to establish relationships with hydrology, soil properties and porewater chemistry. Vegetation cover, density, frequency, and importance values were assessed in late spring by visually estimating percent cover for all taxa and determining stem density for vascular taxa using 1 m2 quadrats along transects. Forty-seven vascular and five bryophyte taxa were documented.

Hierarchical cluster analysis and nonmetric multi-dimensional scaling indicated the plant communities at each site differed and consisted of multiple vegetation stands. Soil or porewater base status and water depths contributed to vegetation differences among the wetlands, while within the wetlands, light intensity and water chemistry also influenced community development. The first wetland (Martins Fork), with Osmunda regalis as an indicator species, exhibited the highest species richness for bryophytes and woody taxa due to deeper water levels and weak minerotrophy. Species composition at the second wetland (Kentenia), with Sphagnum palustre as the indicator species, was influenced by gradients in surface or porewater chemistry, light intensity and water levels. Conspicuously different, the third wetland (Four Level) with Poaceae as the indicator taxon exhibited the highest soil and porewater base richness, distinct sunny and shaded areas, and hydrologic gradients. The dissimilarities among the vegetation characteristics of these ecosystems indicated that each wetland supported biological diversity deserving of continued protection.

2009 Impact

Preliminary assessments of the plant communities at the Martins Fork, Kentenia and Four Level wetlands suggest that each site is floristically unique. Variable soil and porewater base richness and water level gradients are expected to diversely affect plant community associations. Species distribution reflecting preferences for sun or shade, soil moisture content, base status, or humidity levels will be compared to other Appalachian wetlands. Unique plant communities with diverse hydrologic, edaphic, and geochemical environments will be identified and their characteristics will be used for a better understanding of their functionality and value as ecological buffers in the Appalachians.