COS 22-1 - Does long-term drought alter the response of soil microbial communities to moisture?

Tuesday, August 9, 2011: 8:00 AM
8, Austin Convention Center
Sarah E. Evans, Kellogg Biological Station, Michigan State University, Hickory Corners, MI, Matthew D. Wallenstein, Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO and Ingrid C. Burke, Department of Ecosystem Science and Management, University of Wyoming, Laramie, WY

Drought is likely to become more frequent and more severe under future climate regimes. Despite microorganisms’ important role in ecosystem function and our extensive knowledge of community responses to disturbance in plant systems, we do not know how microbial communities will respond to extreme moisture events, and whether this response may depend on ecological history. In this study, we tested whether drought history alters the response of active microbial communities to moisture. We sampled soils from 11-year drought manipulations at the shortgrass steppe LTER and subject soils to a range of moisture levels in the lab to investigate changes in microbial community composition and function. We isolated the active community by using BrDU-incorporation and examined composition by pyrosequencing the immunocaptured DNA, and measured decomposition rate by measuring CO2 efflux from 1-year incubations. 


Drought history strongly affected which bacteria species were active in response to moisture. Samples from the same drought treatment in the field were more similar than samples subject to the same lab moisture, although moisture had a stronger influence on community structure at the wettest and driest levels. Although specific taxonomic groups showed different responses to both drought and moisture exposure in the lab, we did not find a strong relationship between phylogeny and drought-response. Respiration rates were significantly different among moisture levels, but drought history did not have a strong effect on the respiration response over a range of moistures. This suggests that drought does select for more tolerant microbial species, and the proportion of the community active under certain conditions is influenced by microbial ecological history. However, our results suggest that these community changes may not affect broad ecosystem-level processes, such as respiration, and community changes may not be predictable based on phylogenetic relations.

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