Tuesday, August 4, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Julie A. Foote, Ecosystem Science & Management, Texas A&M University, College Station, TX and Adria Bodour, Geological Sciences, University of Texas - San Antonio, San Antonio, TX
Background/Question/Methods Introduced invasive plants have altered the structure and function of ecosystems throughout the world. For example, in Texas, Bothriochloa ischaemum var. songarica (King Ranch bluestem) was introduced as an improved pasture grass, but has become an aggressive invader of grasslands and shrublands throughout the state. Although aboveground impacts of this species have been assessed, we know little regarding the impact of this invasive grass on belowground communities and processes. The purpose of this study was to evaluate potential differences in soil microbial communities in a 30 year old restored native grassland versus a 50 year old grassland dominated by B. ischaemum on clay loam ecological sites in central Texas. For both sites, subsequent to the equalization of soil moisture, we extracted and quantified bacterial and fungal ester-linked fatty acid methyl esters (EL-FAME) in conjunction with culturing to evaluate microbial community composition. We also measured pH, C:N ratios, and soil texture. Concentrations of low percentage EL-FAMEs were compared as it was felt that these constituents would be more responsive to environmental shifts.
Results/Conclusions
Low percentage EL-FAMEs revealed that fungi and gram negative bacteria were generally more abundant while gram positive bacteria were generally less abundant in the restored native grassland versus the site dominated by B. ischaemum. These differences were unrelated to the other measured soil properties, suggesting that plant community composition may have been the most important determinant of microbial community structure at these sites. We conclude that grasslands dominated by B. ischaemum have unique microbial community composition compared to restored native grasslands, and suggest that these differences in composition may be accompanied by differences in belowground community function. In light of the results of our study, examination of the microbial community during restoration of invaded grasslands to more native condition is warranted in central Texas.
