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 THE EFFECTS OF FUTURE GLOBAL CHANGE ON ARBUSCULAR MYCORRHIZAL FUNGI AND SOIL CARBON: USING URBANIZATION AS A SURROGATE FOR FUTURE CONDITIONS IN FIELD STUDIES(2012) Wolf, Julie; Needelman, Brian; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Carbon, fixed photosynthetically by plants, cycles through plant, microbial biomass, soil, and atmospheric carbon pools. The effects of global change on this cycling will impact future levels of atmospheric carbon dioxide, but are poorly understood. In urban areas, temperature and carbon dioxide concentrations are often elevated to levels that simulate near-future climate changes. These elevations are not sudden, uniform step increases but are gradual and variable; as such urbanization may provide a means to simulate the effects of near-future climate changes. The dissertation research encompasses two studies utilizing urban macroclimate to study the effects of future climate change. In the first study, plots containing a common imported soil and seed bank were established at three locations along a 50 km urban-to-rural transect. In these plots, plant community development, temperature, carbon dioxide concentrations, and other factors had been monitored for five years. Subsequently, arbuscular mycorrhizal fungal structures in bulk soil were quantified. These fungi receive carbon directly from plant roots, grow into bulk soil, and can transfer immobile soil minerals to their plant hosts. In contrast to expectations, fewer fungal structures were found closer to the urban side of the transect. The second study was an observational study of soil carbon in minimally managed, long-undisturbed soils located at varying distances from urban areas. In sampling sites at 62 golf courses, similar communities of cool-season grasses had been undisturbed for at least 25 years. At each site, total and active soil carbon and many potential explanatory factors were measured and examined with multiple regression analysis. Contrary to expectations, soil carbon was positively correlated with warmer February-only mean daily minimum soil temperatures, suggesting that winter temperatures are more important than mean annual temperature for soil C storage in temperate grassland. Other correlations, including positive correlations with soil cation exchange capacity, soil lead levels, and tropospheric ozone exposure during the peak ozone season, were also detected. Potential mechanisms for the detected relationships are explored. The results of both experiments demonstrate that commonly-held expectations based on single-factor global change experiments or models are not always borne out in complex natural systems.Item Carbon Storage and Potential Carbon Sequestration in Depressional Wetlands of the Mid-Atlantic Region(2011) Fenstermacher, Daniel E.; Rabenhorst, Martin C; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With recent concern over climate change, methods for decreasing atmospheric levels of greenhouse gasses such as CO2 have been of particular interest, including carbon sequestration in soils that have depreciated levels of carbon from cultivated agricultural crop production. The Delmarva Peninsula contains many Delmarva Bay landforms, which commonly contain wetlands. Five pairs of Delmarva Bays were selected to examine change in carbon stocks following conversion to agriculture and to assess the potential for carbon sequestration if these soils were to be restored hydrologically and vegetatively. A loss of approximately 50 % of the stored soil carbon was observed following the conversion to agriculture. If these agricultural soils were to be restored, the wetland soils within the Delmarva Bay basin are predicted to sequester a total of approximately 11 kg C m-2 and the upland soils of the rim would be expected to sequester a total of approximately 4 kg C m-2.Item EVALUATION OF LABILE SOIL CARBON TEST FOR PREDICTION OF SOIL PRODUCTIVITY RESPONSE TO ORGANIC MATTER MANAGEMENT(2005-01-05) Lucas, Shawn Thomas; Weil, Ray R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A KMnO4 oxidation method for estimating labile soil C (CL) was evaluated for use in a soil testing mode to identify soils where soil quality and productivity is likely or unlikely to respond positively to increased levels of CL. Four sets of paired fields of the same soil series (within each set) but contrasting soil management history (continuous cropping vs. long-term sod) were studied. Fields with sod history initially tested higher in total soil C and CL than fields with cropped management history. Within each field two treatments (winter rye cover crop or no cover crop) were applied in each of four blocks. Crop and soil functional responses to rye, when significant, were higher in fields that initially tested lower in CL indicating that the KMnO4 method used has some predictive value as a soil test. The method could be used in field testing kits for evaluation of soil C.