Soil microbial responses to drought and rewetting

Ecosystems will likely be exposed to extreme weather events due to climate change. These extreme events include altered rainfall patterns such as frequenter and prolonged drought and rainfall events. It is well known that soil moisture has a direct effect on soil microbial activity. However, less is know about the legacy of these drought and rainfall events on plant species or microbial functioning during an additional stress event. Here, we studied how changes in soil microbial communities due to an initial drought and rainfall event can influence soil microbial functioning or plant species during a second drought and rainfall event. In two microcosm experiments, soil microbial communities were exposed to two or multiple cycles of drying-rewetting events in the lab. Soil microbial community composition of potentially active and total communities, bacterial growth and/or soil respiration were determined. In a mesocosms experiment, soil was exposed to four weeks of drought followed by extreme rainfall in a full factorial design. After three weeks, soil was sampled and DNA was extracted and amplicon sequenced to determine the community composition of soil bacteria and fungi. In addition, plant responses were measured. The results indicated that the first drought and rainfall event determined the functioning of the microbes that were exposed to a second rainfall event. The microbial communities differed between different treatments. In addition, microbes became in a more active state when they were exposed to multiple cycles. Different drought and rainfall events changed the composition of the microbial community thereby explaining the altered response of the plant community to an additional drought and rainfall event. As such, soil microbial responses to drought and rainfall events and their legacies are important to consider for ecosystem functioning.