Intermediate Disturbances Enhance Microbial Enzyme Activities in Soil Ecosystems

The Intermediate Disturbance Hypothesis (IDH) posits that maximal plant biodiversity is attained in environments characterized by moderate ecological disturbances. Although the applicability of the IDH to microbial diversity has been explored in a limited number of studies, there is a notable absence of experimental reports on whether soil microbial 'activity' demonstrates a similar response to the frequency or intensity of environmental disturbances. In this investigation, we conducted five distinct experiments employing soils or wetland sediments exposed to varying intensities or frequencies of disturbances, with a specific emphasis on disturbances associated with human activity, such as chemical contamination, hydrologic changes, and forest thinning. Specifically, we examined the effects of bactericide and heavy metal contamination, long-term drainage, tidal flow, and thinning management on microbial enzyme activities in soils. Our findings revealed that microbial enzyme activities were highest at intermediate disturbance levels. Despite the diversity in experiment conditions, each trial consistently demonstrated analogous patterns, suggesting the robustness of the IDH in elucidating microbial activities alongside diversity in soils. These outcomes bear significant implications for ecological restoration and management, as intermediate disturbance may expedite organic matter decomposition and nutrient cycles, crucial for sustaining ecosystem services in soils.