NE1021: Hydropedology: Genesis, Properties, and Distribution of Hydromorphic Soils
Statement of Issues and JustificationBecause of the environmental and economic importance of wetlands and coastal resources to northeast, pedologists in this region have been developing expertise in the identification, characterization, classification, and land use interpretations for soils within these areas. In this project, we will establish a framework for the systematic study of saturated, hydric, and subaqueous soils across the northeastern US. This project will focus on: documenting the physical, chemical and morphological characteristics of these soils; establishing soil-landscape and soil-vegetation relationships; and developing an understanding of how these characteristics and relationships vary across the region and with changes in land use.
Soil interpretation rating guides (developed by the Natural Resource Conservation Service, NRCS) list over 30 land use decisions that are dependent upon knowing the depth to seasonal saturation (Soil Survey Staff, 1996). Some of the more important interpretations based on the depth to seasonal saturation include the construction of buildings and roads, surface application of waste, and the use of on-site waste disposal systems (ISDS). Water table depth is also a key factor in identification of wetlands (Environmental Laboratory, 1987). Wetland delineation is a million dollar industry and identification of hydric soils is essential in the delineation process. Of particular interest is identifying the variation in seasonal tables in soils that are wet, but where certain properties of the soil mask the typical morphology found in most wetland soils. These so called "problem soils" may include sandy soils, soils derived from Triassic redbed sediments, carboniferous and other dark parent material soils, soils formed in pre-weathered parent materials, soils having episaturation, and certain soils in floodplains. These problem areas occur across the entire region and need to be addressed from such a perspective.
Inventories of continuously submerged soils, referred to as "subaqueous soils" have been completed in estuarine environments in Maryland (M. Rabenhorst, PI) and Rhode Island (M. Stolt, PI), and are in progress in Maine (L. Osher, PI) and Delaware (M. Rabenhorst, PI). These resource inventories are providing the template for other near shore soil surveys that will be completed in estuarine environments throughout the US. Subaqueous soil inventories will provide numerous interpretations for coastal managers. King (2003) listed over 15 different subaqueous soil interpretations that federal, state, local agencies, and private companies have requested information about. Some of the most common requests have been in regard to: clam stocking, sustainable shellfish production, effects of dredging on benthic ecology, tidal marsh protection and creation, horseshoe crab habitat, dune maintenance/replenishment, and submerged aquatic vegetation (SAV) restoration. Little is known of these subaqueous soils and the associated interpretations. Nothing is known regarding how these interpretations vary across the region.
One of the most important interpretations from an inventory of subaqueous soils may be SAV restoration. Submerged aquatic vegetation such as eelgrass provide nursery habitat for economically important fin and shell fish and are important for sediment and nutrient filtering, nutrient cycling, and buffering wave effects. Aerial coverages of eelgrass beds have severely declined over recent years. Therefore, eelgrass restoration has become a focus of many coastal managers. Eelgrass revegetation and restoration projects cost on the order of $100,000 per acre, but few of these projects have been successful. It is highly likely that the projects fail because of site selection. Eelgrass revegetation sites are commonly located where past eelgrass meadows had been, not at sites where present soil conditions are optimum for success. However, loss of eelgrass tends to result in erosion of the submerged soils. The subsequent soils in the intertidal could be significantly different than those that supported the eelgrass. A detailed knowledge of the relationship between subaqueous soil properties and submerged aquatic vegetation is essential for improving the success of eelgrass revegetation efforts. An understanding of the eelgrass-subaqueous soil system will help resource managers identify the sites where revegetation efforts can be most successful (Bradley, 2001). Although eelgrass is the dominant SAV across the northeast region, knowledge of how well eelgrass-subaqueous soil relationships hold across the region with the breadth of tidal ranges and gradient of temperatures is unknown.
Saturated soils store significantly more carbon than well-drained soils per unit area. Most investigations, however, focused on quantifying soil carbon sequestration in better drained landscapes. Studies of carbon storage and loss in fresh water (Garnett et al. 2001) and coastal (Choi 2001) marshes are an excellent start, but these only describe a small subset of organic wetland soils. While marshes and the organic soils that support them are important ecosystems, the majority of subtidal soils are mineral soils. Very little is known about the amount of C sequestered in these subaqueous soils. As a result, predicting the impact of regional scale land use change, climate change, or rising sea levels on C storage in coastal zone is difficult at best. The results of this research will enable us to improve our estimates of the amount of carbon stored in seasonally saturated, wetland, and subaqueous soils in the northeastern US. In addition, the work will better enable us to model the effects of land use and climate change on soil C pools in seasonally saturated or hydric soils.
Working within the proposed regional framework will allow for testing of hypotheses regarding carbon storage, soil-water table relationships, and subaqueous soil characteristics across climatic gradients, across parent material types (coastal plain, residual, and glacial), and for the subaqueous soils and marsh settings across a diverse range in daily tidal fluctuations. For example, are subaqueous soil interpretations developed for restoration of eelgrass in Maryland estuaries the same for estuaries in Maine? Testing such a hypothesis is not possible for a single investigator working within a single state and must be done across the region. 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, ACOE, EPA, all work in a region-wide context. In addition, working groups such as the New England Hydric Soil Technical Committee and Mid-Atlantic Hydric Soils Committee (see NEHSTC, 2004 and MAHSC, 2004 as examples of their work), who offer guidance to regional regulatory bodies like the New England Water Pollution Control Commission (http://www.neiwpcc.org/), need soils information that is not restricted by state boundaries. 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.
One of the goals of this project is to develop testable hypothesis and collect critical data in order to strengthen our standing in a very competitive field of scientists pursuing funds related to wetlands, environmental quality, global change, coastal environments, and natural resources. The proposed multi-state project meets the USDA-NRI criteria of studies that "address key problems of regional and multistate importance" and will strongly advance our efforts as we compete for funds from the NRI in the area of Natural Resources and Environmental Quality. As an example, investigators working on this multistate project proposal are preparing proposals that focus on subaqueous soils for the Soils and Soil Biology program. In addition, this proposal will provide additional leverage as we strive to compete for funds directed toward water quality, restoration, ecosystem sustainability, and coastal resource initiatives from agencies such as EPA, NOAA, ACOE, and Sea Grant. In the end the proposed project will support our long-term goal to provide soils based information to natural resource managers for determining how resources and ecosystems should be managed to insure sustainability and health.
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