Climate change is expected to be multi-faceted with annual mean temperatures expected to rise 2-5oC, rainfall amounts to increase and frequency of occurrence to decrease. Currently, much of the research in this area has been centered on the effect of global warming on carbon fixation, storage, and plant communities, with little research focused on microbial communities. Microbial communities play a vital role in nutrient mineral cycling and are a large source of CO2 via litter degradation. As microbial diversity and community composition are known to be critical factors in determining ecosystem stability and function, it is necessary to understand how global warming affects the diversity within microbial communities. Recent advances in sequencing technology have increased the depth at which we are able to probe and survey microbial diversity in a given environment. Using a pyrosequencing approach, two randomly chosen paired plots (two control and two warmed) were surveyed from an artificially warmed tall grass prairie site (Kessler Farm) in Central Oklahoma. Plots were constantly heated 2.0oC above ambient using an above plot infrared heater since 1999. DNA was extracted from soil cores taken in April 2005 from randomly chosen plots and the V3 region of the 16S rRNA gene was amplified, pyrosequenced and analyzed for abundance and diversity.
Results/Conclusions
Control and warmed libraries consisted of 51069 and 45547 sequences respectively, which clustered into 5711 and 6109 operational taxonomic units (OTU0.03) respectively. Examination of the relative abundance of phyla suggest that warming increased Proteobacteria, Acidobacteria, Chloroflexi, Verrucomicrobia and Planctomycetes numbers in soil by 27, 67, 32, 208, and 268% respectively, while Actinobacteria abundance decreased by 62%. Diversity ordering methods (Rényi, Hulbert, Rarefaction, and Right-tail sum) indicated that the total bacterial population, as well as the Actinobacteria, Acidobacteria, Planctomycetes, and Verrucomicrobia are more diverse, while Chloroflexi and Gemmatimonadetes were less diverse in the warming treatment. S-libshuff indicated a significant shift in community membership in the Planctomycetes, Gemmatimonadetes, and Chloroflexi. Our data suggests that the warming treatment positively impacted both abundance and diversity of the soil microbial community. We argue that this observed stimulation is a reflection of earlier phenological changes observed in the plant community, which results in increased labile carbon and nitrogen pools. The impact of these observed changes on soil carbon and nitrogen storage capacity is discussed.
