Effects of anthropogenic disturbances on soil microbial communities in oak forests persist for more than 100 years

Land-use change and land-use intensification are considered amongst the most influential disturbances affecting forest diversity, community structure, and forest dynamics. Legacy effects of land-use changes in ecosystem functioning and services may last several hundred years. Although numerous studies have reported the short-term legacy effects of past management, analyses of long-term responses (>100 years) are still lacking. Here, we demonstrate shifts in soil microbial community structure and enzymatic activity levels resulting from a long-term past disturbance intensity gradient in oak forests (former arable farming - former heathland farming - ancient forest). Differences in microbial community composition among sites with contrasting historic land-use were related to differences in soil chemical properties and abundances of arbuscular mycorrhizal fungi, saprotrophic and ectomycorrhizal fungi, and actinobacteria. Both microbial biomass and enzymatic activity levels were distinctly lower in ancient forests compared to historically cultivated sites (i.e. agriculture or heathland farming). We found evidence that past land-use has long-lasting impacts on the recovery of soil community development, much longer than commonly assumed. This in turn highlights the importance of ecological continuity for ecosystem functioning and services. Conservation management, focussing on the stability and diversity of forest ecosystems, therefore needs to consider past land-use legacies for evaluating ecosystem functions (such as soil ecological processes) and for evaluating effective strategies to adapt to environmental changes.