Microbial communities provide many critical ecosystem functions to soils, including organic matter decomposition and nutrient cycling. Microorganisms use a variety of metabolic processes to break down the complex macromolecules in plant leaf litter into more labile constituents such as sugars, amino acids and organic acids. The goal of this research is to evaluate the importance of edaphic factors on microbial decomposition at the Wild Basin Wilderness Preserve in Austin, TX. We hypothesized that soil characteristics would influence the structure of microbial communities due to varying environmental requirements. In order to test our hypothesis, we collected triplicate soil samples at six sites on September 17th, 2016 and January 28th, 2017. We measured soil pH, soil moisture and soil organic matter content using the loss on ignition method. We used two different methods for understanding microbial decomposition at these sites. First, we buried tea bags at six locations for 90 days, and then measured the mass loss in the lab. Then, we evaluated microbial carbon substrate utilization of 32 different carbon compounds with BIOLOGÒ EcoPlates. Substrate utilization diversity at individual sites was calculated based off the different types of carbon and the extent to which microbes metabolize specific compounds.
A Mantel test suggests that edaphic factors influence carbon substrate microbial utilization. Tea bag decomposition indicates that sites with low overall soil moisture (9%) had higher rates of decomposition than those with higher soil moisture (12-15%). As soil composition alters so does the microbial communities utilization of specific carbon compounds. Future research objectives include measuring soil decomposition of different plant litter types in situ and through laboratory incubations, and the taxonomic characterization of soil microbial communities using 16S rRNA gene sequencing.