Compounded disturbance chronology modulates the resilience of soil microbial communities and N-cycle related functions.

The recent scientific literature highlights the growing interest of overcoming the uncertainty related to the cumulative impacts of multiple disturbances of different nature in all ecosystems. With global change leading to acute environmental disturbances, and ever-rising anthropogenic activities causing exposure to ‘novel stressors’, there is a significant increase in the possible number of interactions between disturbances that can generate complex, non-additive effects on ecosystems functioning as demonstrated in recent studies. However, we have no information about how the chronology of disturbances can affect ecosystems functioning is unknown even though there are increasing evidence that community assembly history dictates ecosystems functioning. Here, we experimentally questioned the importance of the disturbances chronology in modulating the resilience of soil microbial communities and N-cycle related functions. We studied the impact of 3-way combinations of global change related disturbances on total bacterial diversity and composition, on the abundance of N-cycle related guilds and on N-cycle related activities. We determined that repeated disturbances of the same nature can either lead to long-term resilience or global drift of N-cycle related functions concomitant with diversity loss. When considering disturbances of different nature, we demonstrated that the chronology of compounded disturbances impacting an ecosystem determines the aggregated impact on ecosystem properties and functions. Finally, we showed that surveying changes in bacterial community composition can help predict the strength of the impact of compounded disturbances on N-related functions and properties.