Bacterial Diversity Patterns Differ in Soils Developing in Sub-tropical and Cool-Temperate Ecosystems.

Microbial diversity patterns have been surveyed in many different soils and ecosystems, but we are unaware of studies comparing similar soils developing from similar parent materials in contrasting climates. In 2008, developmental chronosequences with ages ranging from 105 to 500,000 years across Georgia (GA) and Michigan (MI) were studied to investigate how bacterial community composition and diversity change as a result of local environmental gradients that develop during pedogenesis. Geographic factors were studied between and within locations spanning two scales: (1) regionally between 0.1 and 50 and (2) ∼1700 km apart. The diversity was surveyed using high-throughput pyrosequencing, and variance partitioning was used to describe the effects of spatial, environmental, and spatio-environmental factors on bacterial community composition. At the local scale, variation in bacterial communities was most closely related to environmental factors (r = 0.59, p = 0.0001). There were differences in bacterial communities between the two locations, indicating spatial biogeography. Estimates of bacterial diversity were much greater in MI (numbers of OTU, ACE, and Chao1) and remained 2-3× greater in MI than GA after removing the effect of soil properties. The large differences in diversity between geographically separated bacterial communities in different climates need further investigation. It is not known if the rare members of the community, which contributed to greater bacterial diversity in GA relative to MI, play an important role in ecosystem function but has been hypothesized to play a role in ecosystem resiliency, resistance, and stability. Further research on the link between bacterial diversity and spatial variability related to climate needs further investigation.