Science
Currently, the laboratory is conducting research on:
- changes in soil physical, chemical and mineralogical properties due to disturbance and how ecosystems change in response;
- soil genesis, classification, and mapping;
- problematic soil physical and chemical properties in urban environments and their management;
- land use assessment based on soils.
Some of our existing projects.
Soil Genesis, Classification, and Mapping
Chemical and mineralogical cementing agents in fragipans from Pennsylvania parent materials
Image courtesy of Steve Dadio.
The fragipan diagnostic subsurface horizon is identified in soils on diverse landscapes throughout the world. In Pennsylvania, fragipans have been identified as having formed in aeolian, alluvial, glacial, peri-glacial (colluvial), and residual (including numerous geologies) parent materials. Fragipans are also identified in soils of varying age in Pennsylvania; in inceptisols, alfisols, and ultisols. Numerous theories abound as to the formation of the fragipan and what are the binding agents for this dense, root and hydraulically restrictive subsurface horizon. We collected soil samples of fragipans in Eastern and Central Pennsylvania that formed in a variety of parent materials and geologies. Pedogenic opaline silica was quantified by tiron extraction and crystalline and amorphous Fe and Mn structures via citate dithiotnite and acid ammonium oxalate. Structures and cementing agents within fragipan horizons were examined utilizing a Focused Ion Beam (FIB) and Transmission Electron Microscope (TEM).
Collaborators: Stephen Dadio: CMX Engineering; Patrick Drohan, PSU Soil Characterization Lab; Trevor Clark, PSU MRI; and Sarah Ogden, PSU SCL.
Geomorphic relationships in the fragi taxon across Pennsylvania: clues to genesis and cementation mechanisms.
Image courtesy of Steve Dadio.
NRCS Soil Survey data indicates that there are 33,081 km² of soils with fragipans occurring in every county of Pennsylvania (28% of the state’s area). The horizon is known to limit development and production potential for land uses dependent on good drainage and deep rooting. Previous research in Pennsylvania has found that fragipans form primarily in transported parent materials, are more dense and thicker in areas of poor drainage, and are present deeper in the soil profile in areas of steep slopes. However, the criteria used to identify the horizon are based on subjective-non-laboratory based measures that make absolute recognition impossible and the likelihood of the taxon representing gradations of occurrence more likely. The completion in 2007 of Pennsylvania’s SSURGO mapping provides the opportunity to examine models of fragipan development with high resolution digital mapping data. We selected soil mapping units with a dominant fragi taxon (soil associations, mine land, urban land areas removed from analysis) to examine taxon distribution within physiographic provinces. Within provinces, NRCS Official Series Description data and surficial geology (Pennsylvania Geologic Survey data) was also used to discern relationships in fragipan density between parent material and elevation, aspect, slope and geomorphology (potential peri-glacial influence of loess contributions) with fragi taxon distribution. We also examine differences in taxons by physiographic province at the sub-order, great group and sub-group levels.
Collaborators: Patrick Drohan, PSU Soil Characterization Lab, Sharon Waltman, USDA-Natural Resources Conservation Service National Geospatial Development Center, West Virginia University; Brian Bills and Doug Miller, PSU Center for Environmental Informatics; Stephen Dadio, CMX Engineering; Ed White, USDA-NRCS, State Soil Scientist, Pennsylvania.
Extent of subaqueous soils in freshwater ecosystems of Pennsylvania
Recent research conducted on subaqueous soils by Demas and Rabenhorst (1999, 2001), Demas et al. (1996), and Bradley and Stolt (2003) has led to the classification of sediment under up to 2.5 m of water (Soil Survey Staff, 1999; Bradley and Stolt, 2003) as soil according to U.S. soil taxonomy. Such soils are important for supporting aquatic life, which in turn supports other aquatic fauna. Identification of these substrates as soil was an important step in the evolution of soil science and strongly stresses the importance of subaqueous soil environments and the valuable services they provide to society in the form of support for freshwater and estuarine fisheries around the world and support of marsh and wetland ecosystems important in flood protection. Around the United States, many subaqueous soils are experiencing substantial anthropogenic disturbance from surface runoff laden with pollutants and from dredging. Research by the U.S. Environmental Protection Agency (EPA) found that nationwide recreational and commercial finfishing profits in estuarine environments, where subaqueous soils occur, totaled $30 billion annually. In addition, the EPA estimates that estuaries provide habitat for 75% of the catch of all commercial fish species and approximately 28 million jobs nationwide. Our research in Pennsylvania is addressing the potential extent of subaqueous soils in freshwater ecosystems and the characteristics we can use to identify soil mapping units.
- Demas, G.P., and M.C. Rabenhorst. 1999. Subaqueous soils: Pedogenesis in a submersed environment. Soil Sci. Soc. Am. J. 63:1250-1257.
- Demas, G.P., and M.C. Rabenhorst. 2001. Factors of subaqueous soil formation: A system of quantitative pedology for submersed environments. Geoderma 102:189-204.
- Bradley, M.P., and M.H. Stolt. 2003. Subaqueous soil-landscape relationships in a Rhode Island estuary. Soil Sci. Soc. Am. J. 67:1487-1495.
Soil physical, chemical, and mineralogical development associated with Cercocarpus ledifolius stands
- Vegetative induced state and transition indices related to soil development over time
- Controlling factors in pedogenesis: influence of atmospheric dust on shallow horizon mineralogy
- N and P dynamics in relation to mineralogical development over time
Estimating the rate of soil formation is one of the greatest challenges in soil science. It is also of great importance to many science fields that use soil data (hydrological modeling, climate change research, landscape stability, and earthquake risk being a few examples). While it is known that plants affect soil development, information on soil formation is especially lacking in arid ecosystems under the influence of long-lived plant species such as curlleaf mountain mahogany (Cercocarpus ledifolius, Rosaceae). Because of the long-life of C. ledifolius, the species can provide valuable information on soil development over long periods of time. Preliminary data from southern Nevada suggests that soils under C. ledifolius exhibit significant soil development as compared to soils in open areas. This is especially important for landscape stability and development in the Intermountain West since C. ledifolius sites are often on dry, rocky, low-productivity slopes that otherwise support minimal tree growth. Because C. ledifolius may attain ages in excess of 1000 years and may re-establish in the same positions on the landscape, the potential for quantifying soil development and deriving rates of several soil formation processes is great. Since many models predict the expansion of arid ecosystems with global climate change, C. ledifolius will likely play an even greater role in soil development in the future.
Land Use Assessment Based on Soils
Extent of fragi taxons on CRP/CREP lands and potential environmental, management and economic effects on biofuels production due to fragipan soil limitations.
Concern is growing across the U.S. among land managers who are seeing increasing numbers of farmers not renewing contracts to keep marginal lands enrolled in the U.S. Department of Agriculture’s (USDA) Conservation Reserve Program (CRP) and Conservation Reserve Enhancement Program (CREP). Driving this trend in agricultural land use change is a trend in the development of ethanol production techniques and initiatives that would use ethanol as a fuel source to help achieve energy independence. In Pennsylvania many CRP/CREP lands have a subsoil horizon known as a fragipan, which is partly responsible for drainage/rooting problems resulting in poor crop yields. Production of biofuels on such lands poses risks of crop failure and potential increases in surface water pollution due to soil destabilization and surface erosion. However, if the effects of the fragipan can be minimized, or eliminated, then using such lands under careful agricultural management techniques could help farmers achieve financial stability with biofuels while also providing habitat to many species of wildlife. We examine the extent of fragipans on CRP/CREP lands and the potential environmental, management and economic effect on biofuels production due to the fragipan’s soil limitations.
Collaborators: Patrick Drohan, PSU Soil Characterization Lab; Sharon Waltman, USDA-Natural Resources Conservation Service National Geospatial Development Center, West Virginia University; Brian Bills and Doug Miller, PSU Center for Environmental Informatics; Carrie Foster, MGIS program, PSU; Stephen Dadio, CMX Engineering; Ed White, USDA-NRCS, State Soil Scientist, Pennsylvania.
CRP, CREP or Biofuel Production — Which is the most profitable?
Farmers in Pennsylvania with land enrolled in the Conservation Reserve Program (CRP) or Conservation Reserve Enhancement Program (CREP) are currently evaluating whether it is economical for them to maintain their CRP/CREP leases or switch these lands into biofuels production (corn or switchgrass). Not renewing CRP/CREP leases and placing these lands into production could jeopardize the benefits Pennsylvania has gained from these conservation programs over the years including decreased soil erosion, improved stream water quality, and increased wildlife habitat. We conducted a geospatial analysis of CRP/CREP lands in Pennsylvania to derive soil limitations and potential yield in order to determine the cost of growing corn, switchgrass or leaving land enrolled in the CRP/CREP program. Data on potential yields for corn and interpolated values for switchgrass, were derived from data available in the USDA-NRCS Soil Ratings for Plant Growth (SRPG) dataset. The results of this analysis will ultimately form the basis for an interactive web map-based decision support tool designed for farmers that will provide them with the expert guidance needed to make the decision to leave their land enrolled in CRP/CREP or to place it back in production with switchgrass or corn.
Collaborators: Carrie Foster, PSU-MGIS program; Patrick Drohan, PSU Soil Characterization Lab; Doug Miller, PSU Center for Environmental Informatics.
Recent Past Projects
Cultural implications of architectural mortar and plaster selection at Mesa Verde National Park, Colorado
Mesa Verde is one of America’s most fascinating National Parks. Located in the Four Corners region of the Southwestern United States, the park is home to hundreds of prehistoric cliff dwellings once occupied by the Ancient Puebloans. Our research at Ruin 12 and Spruce Tree House: (1) examines the temporal consistency, or lack thereof, in mortar source selection between two sites; (2) examines patterns of mortar selection at distinct locations within each site in an effort to determine the extent and makeup of the mortar source primary resource access group; (3) and provides a regional perspective on the similarities and differences in mortar procurement. In order to provide a thorough geochemical characterization of mortar and plaster samples, analytic techniques including x-ray diffractometry (XRD), inductively coupled plasma – mass spectrometry (ICP-MS), electron microscopy (SEM-EDS) have been utilized. Results of this research indicate the existence of a temporal trend in mortar selection at Spruce Tree House very similar to that originally described for Mug House by Rohn (1971). Early cliff dwelling masons preferred using a combination of mesa top loess and sandy soil for construction. During the middle period of occupation, this gave way to residual soil sources closer to the construction efforts in the cliffs. Finally, during the latest period of cliff house construction, masons began incorporating crushed shale into the mortar. This temporal trajectory of mortar selection has now been shown at two Mesa Verde sites, and may extend to a large portion of similar cliff house sites within the Mesa Verde proper. The results from Spruce Tree House also indicate that households occupying the site at any one time shared equal access to mortar sources. Plaster analysis using SEM-EDS identified rich white-washes as elementally distinguishable layers of calcium carbonate. Tan and red earthen colored layers exhibited more subtle elemental differences. Results suggest a variety of source materials were used for plastering, as well as a variety of recipes depending on the intended effect. This project was undertaken by Shane Rumsey, MA Candidate, Dept. of Anthropology, Univ. of Nevada, Las Vegas. Collaborators: Shane Rumsey; Dr. Karen Harry (Dept. of Anthropology and student advisor); Patrick Drohan (PSU Soil Characterization Lab); Rebecca Carr (currently Casa Grande Ruins National Monument).
The development of vesicular horizons and porosity in arid environments:
The vesicular horizon is a surface, or near surface, soil horizon comprised of tiny non-connected circular, ovoid, or prolate pores commonly called vesicles. The horizon has been found to form in soils of a variety of parent materials deposited via eolian processes as dust and is often comprised of fine textures. Vesicle pore formation is hypothesized to occur by several different processes with the most widely accepted being entrapped air and soil particle movement following soil wetting (air entrapment due to a wetting front from rain or snowmelt). Field research on hydraulic properties of vesicular horizons has noted significantly lower hydraulic conductivities in vesicular horizons on surfaces of increasing geomorphic age due to greater accumulations of clay. Due to it’s affect on water movement into arid soils, the vesicular horizon may be the most influential soil horizon in arid landscape geomorphology and pedogensis. This project is being undertaken in the Lake Mead National Recreation Area by Maureen Yonovitz, MS Candidate in Geoscience (soil science emphasis), Dept. of Geoscience, Univ. of Nevada, Las Vegas.
Accelerated pedogenesis due to exotic species invasion: Bromus tectorum’s (cheatgrass) effect on soil physical and hydrological properties.
Introduction of Bromus tectorum (cheatgrass) into western rangelands has had a profound effect on the diversity and health of native ecosystems. Introduced in the late 19th century, B. tectorum has rapidly out-competed native species and colonized large areas of the Great Basin region. The objective of this research is to assess changes in soil physical and hydrologic properties on former A. tridentata sites now invaded by B. tectorum and to quantify the scope of the alterations through time. Study site selection in northern Nevada (south and north of Winnemucca), was based upon a range of A. tridentata stand replacing fire histories spanning approximately 20 years and subsequent colonization of each fire site by B. tectorum. Fire sites sampled were invaded by B. tectorum following a single fire event; the earliest plot was burned in 1985 with subsequent sites having fires in 1987, 1998, and 2002. Sites characterized by A. tridentata, and not burned, were sampled as controls. To assess soil physical and hydrological properties measures of aggregate stability; hydrophobicity; bulk density; surface strength; surface roughness; and infiltration (double-ring and tension infiltrometer) were made. T-test results indicate significant increases in the percent silt and clay particle size fractions and a decrease in the sand particle size fraction with colonization by B. tectorum. B. tectorum sites exhibit an increase in bulk density, aggregate stability, and surface strength along with a decrease in surface roughness and saturated conductivity; no significant differences in unsaturated conductivity were seen via tension infiltrometer measurements. Sand sieve fractions indicate an increase in very coarse, coarse, and medium sand fractions and a decrease in fine and very fine sand fractions on B. tectorum invaded sites. Results suggest that B. tectorum invasion is altering soil physical properties and in turn, surface hydrology. This project was recently completed by Joshua Boxell, MS Candidate in Geoscience, Dept. of Geoscience (soil science emphasis), Univ. of Nevada, Las Vegas (now at Texas Tech (Dept. of Plant and Soil Science) pursuing a PhD with Dr. Wayne Hudnall).
