Long term effect of dry-rewetting stress on functional response of soil prokaryotic communities

Soil microorganisms are key actors in all biogeochemical cycle. However little effort has been paid to incorporate them to predictive models of future climate change. We investigated the variation of community composition of soil prokaryotes to dry-rewetting stress using a metabarcoding approach. We prepared set of glass bottles with soil treated by various frequency of rewetting and duration of desiccation. Emission of methane, carbon dioxide and nitrous oxide were measured every week while soil samples were taken each month for analysis of genomic DNA. Our results show that diversity indices significantly increase in soils under short term drought and soil rewetted after long term drought. Mainly due to higher frequency of disturbance and rapid physiological activation of inactive microbial community during desiccation which promotes higher niche partitioning and thus allow colonization by diverse organisms. Taxon related to nitrifier and lignin decomposer are significantly higher under dry rewetting stress condition and are directly correlated to greenhouse emission. NTI revealed strong phylogenetic relatedness of soil prokaryotic communities across all treatments and incubation time suggesting that desiccation and rewetting events is a strong biological filter shaping species assemblies. These results suggest that prokaryotes that are well adapted to extremes stressful conditions such a long-term desiccation will released more greenhouse gases that should be taken into account when modeling climate change as a positive feedback.