OOS 73
Rewetting Dry Soil: The Century’s Unifying Problem in Soil Microbial Ecology

Thursday, August 13, 2015: 1:30 PM-5:00 PM
316, Baltimore Convention Center
Annelein Meisner, Lund University
Johannes Rousk, Lund University
Johannes Rousk, Lund University
A pulse of carbon dioxide (CO2) is released when water is added to dry soils. These pulses may have profound ecological importance and can dominate the annual heterotrophic respiration of terrestrial ecosystems. This phenomenon was already observed about a century ago, and has been termed the ‘Birch effect’ after one of its first observers. Pulses of CO2 are often assumed to be microbial mediated. However, a century of work shows that the connection between the CO2 pulse released when rewetting a dry soil and the microbial decomposers require a more nuanced explanation. Here, we will consider the microbial dynamics and strategies to describe the ecosystem response to drying-rewetting events. The explosive dynamics of the rewetting pulse creates an excellent arena for elucidating the microbial mechanisms that can characterize ecosystem biogeochemistry and capture temporal dynamics driving ecosystem processes. In addition, the microbial dynamics and strategies during drying-rewetting will become more relevant as the climate continues to change, creating more frequent and extreme fluctuations in rainfall patterns. Our session will synthesize current knowledge on the causes for the respiration pulse upon rewetting a dry soil and highlight fruitful avenues for future research. The session starts with an introduction to define the current state-of-the-art understanding of the microbial control of the rewetting pulse. After this, a series of research frontier case studies will offer results and insights from soil ecology, microbial ecology and biogeochemistry. The last presentation will identify the knowns and unknowns in models to account for the microbial control of the respiration pulse upon rewetting. We hope to stimulate an ongoing discussion about how our continued efforts to address one of the most prominent drivers of soil microbes, soil moisture, can elucidate the links between their temporal dynamics and functioning and will lead soil microbial ecology into the new century.
2:10 PM
 New hypotheses and old questions about soil community adaptations to water deficit
Mark Williams, Virginia Tech; Madhavi Kakumanu, Virginia Tech; Li Ma, Virginia Tech; Jinyoung Moon, Virginia Tech; Kang Xia, Virginia Tech
2:30 PM
 The origin of carbon dioxide released from rewetted soils: A poisonous paradox
Fiona Fraser, Cranfield University; Ron Corstanje, Cranfield University; Lynda Deeks, Cranfield University; James A. Harris, Cranfield University; Mark Pawlett, Cranfield University; Lindsay Todman, Rothamsted Research; Andy Whitmore, Rothamsted Research; Karl Ritz, University of Nottingham
2:50 PM
 Impact of soil salinity on microbial growth responses to drying and rewetting
Kristin M. Rath, Lund University; Johannes Rousk, Lund University
3:10 PM
3:20 PM
 Microbial growth dynamics underlying the respiration pulse when rewetting dry soil
Annelein Meisner, Lund University; Erland Bååth, Lund University; Johannes Rousk, Lund University
3:40 PM
 Wet-up response of the microbial community is shaped by soil dry-down patterns
Romain L. Barnard, INRA; Catherine A. Osborne, University of California; Mary K. Firestone, University of California, Berkeley
4:00 PM
 Resuscitation of the rare biosphere contributes to the pulse of ecosystem activity following soil rewetting
Zachary T. Aanderud, Brigham Young University; Stuart E. Jones, University of Notre Dame; Noah Fierer, University of Colorado Boulder; Jay T. Lennon, Indiana University
4:20 PM
 Rewetting without rain: Cryptic controls on dryland decomposition in a hyperarid desert
Sarah E. Evans, Michigan State University; Kathryn M. Jacobson, Grinnell College; Peter J. Jacobson, Grinnell College; Mary K. Seely, Gobabeb Research and Training Center (GRTC)
4:40 PM
 Modeling microbial responses to drying and rewetting
Steven D. Allison, University of California; Emma L. Aronson, UC Riverside