Microbial responses to drying and rewetting in soils across a European climate transect

Climate change results in more frequent and intensified drought and rainfall events. The environment exerts a strong control on microbial communities, where drying and rewetting disturbances act as an additional stress that can alter soil processes driving the carbon cycle. Therefore, understanding the environmental control of microbial responses to drying and rewetting events is important to understand the microbial mechanisms controlling the soil C cycle. This study investigated how climate along with soil physiochemical factors affected microbial responses to drying and rewetting. A total of 40 soils across Europe presenting a comprehensive gradient from arctic (N Sweden) to southern Mediterranean (S Greece) climates and wide range of soil properties (SOM: 2-82%, pH: 3.9-7.4, Clay: 8-79%) were exposed to four days of drying followed by rewetting. The microbial growth and respiration responses after rewetting were monitored in high time resolution during 32h. The recovery time of bacterial growth to rates of 50% in undisturbed soil was used as a measure of how resilient microbial communities were to drying and rewetting.

 

The bacterial recovery time after rewetting ranged between 0.6-40h. We found that soils in arid climates had faster bacterial recovery times, suggesting that bacterial communities were more resilient and better adapted to drying and rewetting than those in humid climates, rendering microbial C-use during drying and rewetting more efficient. Furthermore, pH and soil organic matter also had pronounced effects on the resilience of bacterial growth, where acid pH and high soil organic matter resulted in bacterial communities that were slower to recover. In contrast, clay did not have an influence on the resilience of bacterial growth. Our findings suggest that both climate and soil properties are important when determine how soil microbial communities will respond to a drying and rewetting disturbance.