Recent research suggests that increased decomposition rates increase with increasing temperate by enabling decomposers to metabolize more recalcitrant organic matter rather than by increasing the decomposition rate of labile material. More complex, less energy-rich substrates may become more amenable to decomposition, but not all microbes are capable of breaking down low-energy compounds. Thus, an important corollary hypothesis is that the abundance of microbes able to decompose more recalcitrant organic matter increases with increasing temperature. We tested this hypothesis using three methods. First, we assessed microbial community composition using Fatty Acid Methyl Ester (FAME) profiling for soils collected across a series of grassland and cultivated sites with widely varying Mean Annual Temperatures (MAT). Second, we incubated those soils at different temperatures (5, 15, 25, and 35ºC) and characterized impacts on decomposition rates and microbial community composition after 30 and 60 days. Finally, we incubated soils under a given temperature for 150 days and then bumped the temperature 10ºC for the subsequent 60 days, assessing microbial community composition before, during, and after the temperature bumps. Our preliminary data support prior research that total microbial biomass declines as MAT increases, corresponding to lower soil organic matter contents, reduced protection mechanisms for soil microorganisms, and increased decomposition rates. Regardless of MAT, microbial biomass was lower in disturbed versus native grassland sites. Changes in soil microbial community composition and isotopic signatures will be discussed in light of our hypothesis. Results from this research will provide insight into soil organic matter stability under pressures from global warming. Furthermore, it will direct future research on microbial adaptations to global temperature change.