- Soils and Stratigraphy
- Paleoclimate and Paleoenvironmental Change
- Wetland Ecology
- Water Resources
I am interested in understanding the role of changing environments, both natural and human-induced, on geomorphic forms and processes. In my research I utilize data preserved in soils and sedimentary units of playa-lunette systems on the High Plains to interpret environmental change, with records spanning the last ~100,000 years. I incorporate a variety of field and laboratory techniques to establish past soils-climate-vegetation-hydrology patterns to better understand future impacts on playas and other critically important wetlands. Additionally, I have participated in several fluvial geomorphology and water quality related research projects. I utilize GIS/remote sensing techniques to identify and map playa-lunette systems and conduct geospatial analysis of playa-lunette system morphometry and distribution. In my research, I strive to explore new ways to integrate soils and geomorphic data with geospatial technologies to link environmental conditions and hydrologic processes at various timescales in a diversity of settings.
Evaluating the impacts of land use and climate change on playa wetland form and function
Playa wetlands are small, ephemeral, internally-drained wetlands found throughout the High Plains of the central United States. Playas provide a host of critical functions including wetland habitat, groundwater recharge, surface water storage, and water quality improvements.
Although playa wetlands are vital systems of the High Plains, little research has been done examining the impacts of changing climate and land use on playa form and function. Additionally, research on the effectiveness of grassed buffers to mitigate these impacts is lacking. Sedimentation is the greatest threat to playa health, and sediment erosion and deposition patterns are directly linked to watershed land use and regional climate.
To evaluate these issues, I collect soil cores from playas throughout the High Plains, with an emphasis on western Kansas. Cores are analyzed for a variety of properties including color, particle size, organic matter content, bulk density, magnetic susceptibility, and stable carbon isotopes. Age control is provided by collecting radiocarbon samples from soils and buried soils identified in soil cores. This research takes a landscape-scale approach by utilizing computer-based remote sensing/Geographic Information Systems (GIS) techniques to assess playa wetland and watershed properties. These properties have major implications for playas’ abilities to provide wetland habitat, surface water storage, and groundwater recharge.
Lithostratigraphy and paleoenvironments of playa-lunette systems on the High Plains
Playa-lunette systems (PLSs) are geographically isolated, ephemeral wetlands with crescent-shaped dunes adjacent to the wetland. I investigate PLSs on the High Plains to reconstruct paleoenvironment throughout evolution and identify the primary processes and mechanisms of PLS formation and development. I collect soil cores and analyze cores for color, particle size distribution, magnetic susceptibility, and stable carbon isotopes.
Stratigraphic investigations reveal that PLS origin is related to paleotopography, with a depression in the Ogallala Formation underlying playa fill and a ridge underlying lunette fill. Several stratigraphic units are preserved within PLSs (i.e. Sangamon Soil, Gilman Canyon Formation soils and loess, Peoria Loess, Brady Soil, Bignell Loess and Holocene-aged soils) spanning at least from MIS 3 and perhaps as far back as MIS 5. Stratigraphic investigations indicate Marine Isotope Stage (MIS) 3 was characterized by a climate similar to or slightly warmer than present. Effective precipitation was either relatively low or precipitation was more evenly distributed throughout the year, playa floors were exposed for prolonged periods throughout the year. During MIS 2, temperatures were cooler and effective precipitation greater, though precipitation varied cyclically at sub-millennial scales. Slightly wetter phases were associated with water storage in playas and pedogenesis surrounding playas, and drier phases were dominated by sediment remobilization from playa floors and burial of incipient soils on the lunette. The P-H transition was a period in which temperature and C4 plant contributions increased, though multiple shifts of 3–5 °C in 5–10 cm intervals are preserved and correlate to the Bølling-Allerød/Younger Dryas chronosequence. Warming continued throughout the Holocene, and precipitation was highly variable, resulting in multiple Holocene-aged soils throughout PLSs. Thus, the dominant process of PLS evolution has likely varied over time, with dissolution more important during initial development and periods of high effective precipitation. Fluvial-eolian processes increased in importance as playa expansion proceeded and effective precipitation decreased.
Playa-Lunette System Mapping and Geospatial Analysis
Although playas are important landscape elements, few systematic inventories have been conducted, and little is known about their evolutionary history. A comprehensive Geographic Information Systems database was created for Kansas utilizing several geospatial data sources, including aerial imagery, digital raster graphics, and SSURGO soils data. Mapping results indicate there are more than 22,000 playas in Kansas, ranging in size from 0.03 ha to 188 ha, with a mean area of 1.65 ha. More than 80% of all playas are smaller than 2 ha and only about 400 are larger than 10 ha. Results indicate that previous High Plains playa inventories failed to identify most playas smaller than 2 ha because data sources were not of sufficient resolution. Additionally, playa identification criteria have not been consistent for all inventories, making it difficult to compare results and establish trends for various playa attributes across the entire High Plains.
The goal of this project was to develop a comprehensive geospatial database that includes all lunettes associated with playas on the High Plains of Kansas. To accomplish this, 1:24,000-scale digital raster graphics (DRGs) were loaded in a GIS environment, and then visually scanned in one-square-mile intervals for 46 counties in western Kansas. All isolated ridges, identified by subcircular to crescentic-shaped closed contour lines associated with playas, were digitized on-screen and included in the lunette database, followed by limited ground-truthing.
Results of the lunette inventory indicate that 135 playa-lunette systems with a total of 174 lunettes occur in Kansas. Of these, 105 consist of a single lunette associated with a single playa, while 30 playa-lunette systems consist of multiple lunettes associated with a single playa or multiple playas in immediate proximity to one another.