College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Pedogenesis and Hydromorphology of Soils in Mid-Atlantic Barrier Island Landscapes(2014) Rossi, Ann Marie; Rabenhorst, Martin C.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Barrier islands are an important and dynamic component of coastal ecosystems. While a number of studies have focused on the geomorphology, landform dynamics, vegetation patterns, and ecology of barrier islands, there has been relatively little attention paid to the soils, which are an important ecosystem component. The goal of this study was to improve our understanding of the processes and factors influencing soil development on Mid-Atlantic barrier islands. The study was conducted at Assateague Island National Seashore, a barrier island located on the eastern coast of Maryland and Virginia. Study sites ranged in relative surface stability (soil age) and topography, allowing for comparison of the influence of time and soil moisture on pedogenic processes. Soil development was limited because of the young age of the soils and weathering resistant parent material. Evidence of pedogenesis was reflected primarily in accumulations of organic matter and formation of A and O horizons. Carbon accumulation was controlled by the magnitude of carbon inputs (plant biomass), which increased with soil age and wetness, and by decomposition, which was regulated by soil saturation and anaerobiosis. On a global scale, average soil carbon stocks in these soils tend to be low, due to their young age and the environmental stresses faced by plants in these environments (which limits organic inputs). However, relatively high total carbon stocks were documented on the older, forested parts of the island. Soil wetness also affected the development of subsoil horizons. Weak Bw horizons, with brighter chromas and redder hues, were described in relatively well drained, oxidized soils due to slight accumulations of iron (hydro)oxides and organic matter. In poorly and very poorly drained soils iron was reduced, precluding the formation of Bw horizons. Reduced subsoil horizons had low chroma matrix colors. Despite meeting the requirements for hydric soils, many of the wet barrier island soils do not have morphologies typical of hydric soils. Nevertheless, the low chroma colors and organic accumulations at the surface (Oa horizon) proved to be a reliable indicator of soil wetness and became the basis for a proposed set of hydric soil field indicators for Mid-Atlantic barrier islands.Item Pedogenesis in Rain Gardens: The Role of Earthworms and Other Organisms in Long-Term Soil Development(2009) Ayers, Emily Mitchell; Kangas, Patrick; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As bioretention comes into widespread use, it has become increasingly important to understand the development of bioretention soils over time. The objective of this research is to investigate the development of bioretention soils and the importance of ecological processes in the performance of rain gardens. The research includes descriptive studies of pre-existing rain garden soil profiles, laboratory experiments quantifying the effect of earthworms on infiltration rates, and a simulation model describing the influence of earthworms and soil organic matter on infiltration. Surveys of several different rain gardens of various ages provide the first detailed descriptions of rain garden soil profiles. The study revealed a great deal of biological activity in rain gardens, and evidence of pedogenesis even in very young sites. The uppermost soil layers were found to be enriched with organic matter, plant roots, and soil organisms. The field sites surveyed showed no signs of clogging due to the trapping of suspended solids carried in stormwater runoff. Some evidence was found of higher than expected infiltration rates at the field sites, which may be attributable to the effects of bioturbation by living organisms. The ability of earthworms to mitigate the effects of trapped suspended solids on bioretention soils was assessed in the laboratory. Results show that earthworms are capable of maintaining the infiltration rate of bioretention soils, but that their effects have a high degree of variability. This variability is attributed to soil aggregate instability caused by the oversimplification of the ecosystem. Other organisms play a significant role in stabilizing earthworm burrows and casts, and may be essential ingredients in a self-maintaining bioretention ecosystem. A simulation model of the action of earthworms on soil infiltration rates was developed in order to illustrate the physical processes taking place as a result of earthworm activity. The model was calibrated using data from the field study and microcosm experiment. This research is intended to provide a first glimpse into the biological processes at work in rain garden soils. The research shows that soil organisms are present in rain gardens, and suggests that their impact on bioretention performance may be significant.