Temperature Effects on the Soil Microbial Decomposer Community and Decomposition Products.

Decomposition of soil organic matter will be affected by global climate change and at the same time can be a major controller of the greenhouse gasses associated with climate change.  Temperature can affect both the Q₁₀ relationships of resistant soil organic matter and the composition of the microbial population. We set out to examine both changes in the microbial community composition and the microbial intermediates present at several points throughout an incubation. The litter and top 5cm of a C₃↔C₄ prairie soil and the litter layer from pine and cedar plantations planted on the prairie ~70 years ago were sampled on the Nebraska National Forest at Halsey. One percent litter by weight was added to the prairie soil and incubated at 15, 25, and 35C for 90 days. Respiration was measured throughout the incubations on days 10, 30, 60 and 90 air samples were taken for δ¹³C analysis. Stable isotope probing of FAME samples was used to determine community shifts in δ¹³C values to indicate which groups of organisms were utilizing the transplanted litter. BrdU was used to determine which organisms were active by extracting the DNA of microbes and conducting QPCR on the extracted samples. Chloroform fumigations measured changes in microbial biomass and CO₂ samples determined differences in the δ¹³C composition of the microbial community. Pyrolysis molecular beam mass spectrometry was done through out the incubation to determine the chemical composition. The utilization of molecular techniques, tracers and chemical characterization provided important information on the extent and mechanisms of microbial decomposition at different temperatures.