Research Summary:

Austin College is located in the Blackland Prairie, an ecosystem distinguished by its rich black soil and abundant biodiversity. The native grasses that dominate this prairie ecosystem have deep roots that promote infiltration and storage of water and protect the soil from erosion. Historically, periodic fires and grazing by bison helped maintain this ecosystem by eliminating woody vegetation and promoting growth of native plants. Soil microbes located in and around the roots of the prairie plants are also important in the maintenance of this ecosystem. Microbes are key players in the cycling of nutrients and also contribute to helping shape the structure of the soil. With increasing agriculture and industrialization during the 19th and 20th centuries, most of the Blackland Prairie was converted to farmland. Today, less than 1% of the Blackland Prairie remains. With the increasing threat of Blackland Prairie disappearance, restoration has become a top priority. We collaborate with Austin College students to study the impact that soil characteristics, grass species, and restoration management strategies have on shaping soil microbial communities in North Texas Prairies.

Current Projects:

Effects of Plant Species and Soil Characteristics on Rhizosphere Microbial Community Structure in North Texas Prairies

Microbes associated with plant roots (rhizosphere) contribute to nutrient cycling, organic decomposition, and maintenance of soil structure all of which are important in promoting a healthy ecosystem in grassland prairies. Soil type and plant species have both been shown to impact grassland bacterial and fungal rhizosphere communities but the importance of these factors is not fully understood   Grayson County, Texas is situated at the northern end of the Blackland Prairie where soils in the northernmost part of the County are alfisols (which contain high percentages of sand relative to clay) whereas the soils in the rest of the county tend toward molisols or vertisols (which contain high clay contents).  Two grassland sites (Randell Lake and Garnett Prairie) with dramatically different soil textures but similar climate histories are located within a few miles of each other in this region. Two grasses that can be found at both of these sites are Big bluestem and Johnson grass. Big bluestem is a native perennial bunch grass that grows about 1-2 m tall and establishes 3-4 m deep roots that provide channels for water to move into the soil which helps to reduce runoff and soil erosion. In addition, this grass provides good forage for livestock as well as cover and habitat for wildlife.  Johnson grass is an invasive rhizomatous grass that resists displacement and can reduce the overall plant diversity of a grassland community.  We are using molecular methods to compare the structures of bacterial and fungal communities among the prairie sites-grass species treatments.

Effects of Prairie Restoration Strategies on Soil Microbial Community Structure

In 2002, a prairie restoration experiment involving nine fields and three replicated experimental treatments (burning and mowing, grazing and mowing, and burning, grazing and mowing) was begun at the Austin College Clinton and Edith Sneed Environmental Research Area. Initially, the above ground effects of the different land management strategies were monitored.  However, understanding the below ground interactions among soil microbes, soil, and plants is a major step towards achieving prairie restoration. Soil microbial communities play important roles in nutrient cycling, decomposition of organic matter, and soil structure. Because microbes are small and respond rather quickly to environmental changes, detectable shifts in soil microbial communities may precede shifts in the aboveground plant communities during restoration. We are currently using molecular and biochemical methods to monitor the effects that the different land management strategies have on shaping the composition and functions of the bulk soil microbial communities in the experimental fields over time.

Student Research Collaborators:

Recent Presentations and Publications: (Student authors in bold)