Responses of soil bacterial and fungal communities to summer desiccation and rewetting in Mediterranean grasslands: summer precipitation pattern matters
Event details
| Date | 11.03.2014 |
| Hour | 16:15 › 17:15 |
| Speaker | Dr Romain Barnard, Groupe de recherche Agroecologie, INRA Dijon, FR |
| Location | |
| Category | Conferences - Seminars |
Abstract:
The massive soil CO2 efflux associated with rewetting dry soils after the dry summer period significantly contributes to the annual carbon budget of Mediterranean grasslands. Better understanding i) soil microbial adaptation strategies to a seasonally contrasted climate and ii) the response of microorganisms to altered summer precipitation is important to predict future changes in carbon cycling in Mediterranean grasslands. These two axes of research were tackled in both present (DNA-based) and potentially active (rRNA-based) soil bacterial and fungal communities, by sequencing phylogenetic marker genes and quantifying the abundance of these genes and transcripts.
How do soil microorganisms respond to extreme desiccation and rewetting? In three California annual grasslands, soil microbial communities were tracked over a summer season, and in response to controlled rewetting of intact soil cores. Contrasting desiccation-related bacterial life-strategies that were consistent across sites suggest that predicted changes in precipitation patterns may affect soil nutrient and carbon cycling by differentially impacting activity patterns of microbial communities.
How do changes in summer precipitation pattern affect soil microbial response to fall wet-up? Intact soil cores were subjected to three different precipitation patterns over four months (full summer dry season, extended wet season, and absent summer dry season), then the effects of a controlled rewetting event on the soil CO2 efflux pulse and on soil microbial communities were investigated. We found a strong, significant positive relation between change in the structure of the potentially active bacterial community and the magnitude of the CO2 pulse upon rewetting dry soils. We suggest that the duration of severe dry conditions may be important in conditioning the response of the potentially active bacterial community to wet-up and in controlling the magnitude of the CO2 pulse resulting from wet-up events. Thus, predicted changes in summer precipitation pattern may likely affect the metabolic potential of the soil bacterial community and the related magnitude of the rainfall-induced CO2 pulse upon rewetting.
Short biography
As a functional ecologist, Romain Barnard investigates the response of terrestrial ecosystem functioning to global change. His research activities are directed towards better understanding the responses of soil C and N cycles in relation to plant physiology. After a Ph.D. at Paris-Sud University on the effects of elevated CO2 on soil nitrogen cycling, he worked at ETH Zürich for six years in Nina Buchmann’s lab, using stable isotopes to study the controls of time-lags between the assimilation of carbon by the plant and its respiration by the soil. More microbiological aspects of the effects of changes in precipitation patterns on ecosystem functioning were later developed during a two-year stay at University of California, Berkeley in Mary Firestone’s lab. He is now a research scientist at the INRA (French National Institute for Agricultural Research) in Dijon, where he focuses on the effects of precipitation patterns on plant-soil interactions.
The massive soil CO2 efflux associated with rewetting dry soils after the dry summer period significantly contributes to the annual carbon budget of Mediterranean grasslands. Better understanding i) soil microbial adaptation strategies to a seasonally contrasted climate and ii) the response of microorganisms to altered summer precipitation is important to predict future changes in carbon cycling in Mediterranean grasslands. These two axes of research were tackled in both present (DNA-based) and potentially active (rRNA-based) soil bacterial and fungal communities, by sequencing phylogenetic marker genes and quantifying the abundance of these genes and transcripts.
How do soil microorganisms respond to extreme desiccation and rewetting? In three California annual grasslands, soil microbial communities were tracked over a summer season, and in response to controlled rewetting of intact soil cores. Contrasting desiccation-related bacterial life-strategies that were consistent across sites suggest that predicted changes in precipitation patterns may affect soil nutrient and carbon cycling by differentially impacting activity patterns of microbial communities.
How do changes in summer precipitation pattern affect soil microbial response to fall wet-up? Intact soil cores were subjected to three different precipitation patterns over four months (full summer dry season, extended wet season, and absent summer dry season), then the effects of a controlled rewetting event on the soil CO2 efflux pulse and on soil microbial communities were investigated. We found a strong, significant positive relation between change in the structure of the potentially active bacterial community and the magnitude of the CO2 pulse upon rewetting dry soils. We suggest that the duration of severe dry conditions may be important in conditioning the response of the potentially active bacterial community to wet-up and in controlling the magnitude of the CO2 pulse resulting from wet-up events. Thus, predicted changes in summer precipitation pattern may likely affect the metabolic potential of the soil bacterial community and the related magnitude of the rainfall-induced CO2 pulse upon rewetting.
Short biography
As a functional ecologist, Romain Barnard investigates the response of terrestrial ecosystem functioning to global change. His research activities are directed towards better understanding the responses of soil C and N cycles in relation to plant physiology. After a Ph.D. at Paris-Sud University on the effects of elevated CO2 on soil nitrogen cycling, he worked at ETH Zürich for six years in Nina Buchmann’s lab, using stable isotopes to study the controls of time-lags between the assimilation of carbon by the plant and its respiration by the soil. More microbiological aspects of the effects of changes in precipitation patterns on ecosystem functioning were later developed during a two-year stay at University of California, Berkeley in Mary Firestone’s lab. He is now a research scientist at the INRA (French National Institute for Agricultural Research) in Dijon, where he focuses on the effects of precipitation patterns on plant-soil interactions.
Practical information
- General public
- Free
- This event is internal
Organizer
- EESS - IIE
Contact
- Prof. Alexandre Buttler, ECOS / WSL