Monday, November 13, 2006

Woody Plant Invasion of Grassland Alters the Composition of Soil Microbial Communities.

Elizabeth Brewer, Oregon State U/Crop & Soil Sciences, 3029 Agricultural & Life Sciences, Corvallis, OR 97331, United States of America, Terry J. Gentry, Texas A&M University, Department of Soil and Crop Sciences, College Station, TX 77843, Thomas Boutton, TX A&M Univ.-Dep.Rnglnd Ecol., Campus Mail Stop 2126, Campus Mail Stop 2126, College Station, TX 77843-2126, United States of America, and David Myrold, 3017 ALS Bldg., Oregon State University, Oregon State University, Dept. of Crop & Soil Science, Corvallis, OR 97331-7306.

Woody plant encroachment into grasslands alters the quantity and quality of litter and root inputs to soil, and often modifies the storage and dynamics of soil organic matter.  These changes in the functional composition of plant communities and key ecosystem processes may have significant impacts on the structure and diversity of soil microbial communities. Our objective was to examine changes in soil microbial communities in the subtropical grasslands of southern Texas that have been invaded by trees and shrubs. Soils from two depths (0-15 and 15-30 cm) were collected at four positions along transects extending from the center of shrub/tree clusters out into the surrounding open grassland. Phospholipid ester-linked fatty acid (PLFA) analysis and community level physiological profiles (CLPP) were used to characterize the composition of the soil microbial communities. PLFA analyses revealed significant differences in the composition of the microbial communities along the transects at the 0-15 cm depth, but not at 15-30 cm. For example, the ratio of fungal to bacterial PLFAs decreased significantly from the center of the woody clusters (0.09) to the open grassland (0.07).  In addition, CLPP indicated that microbial diversity (Shannon Index) was higher within the woody clusters (3.27) than the surrounding grassland (2.57).  These results indicate that soil microbial communities are altered following woody plant encroachment into this subtropical grassland ecosystem.

Handout (.pdf format, 475.0 kb)