Long-Term Effects of Plant Litter Accumulation and Small Mammal Disturbance on Diversity in Old-Field Succession

Litter accumulation and small mammal disturbances create specific fine-scale microhabitats in grasslands. These microhabitats serve as safe sites and regeneration niches for subordinate plant species and are important in diversity maintenance. Previous experiments manipulating litter and disturbance and studying their effects on diversity revealed complex relationships. However, little is known about the realized net effects of these mechanisms in different types of grasslands. We conducted a long-term observational study exploring these patterns and their effects in successional and mature grasslands. We applied a specific mapping technique: the presences of litter, disturbance, and living plant species were recorded in 5 cm × 5 cm contiguous microquadrats along 52 m permanent transects. Sampling was repeated annually over 10 years. Spatial dynamics and associations with subordinate grassland specialists were evaluated using information theory models. Analyses were performed at increasing spatial and temporal scales. Varying associations were found across years. Negative associations dominated the relationships between litter and local diversity hotspots, while the relationships with disturbances were mainly neutral. When analyses were repeated at longer time scales, consistent negative associations were detected between litter and diversity hotspots. Long-term relationships between disturbance and diversity were negative in old-fields and positive in the natural grassland. To collect more representative and reliable data on the role of plant litter accumulation and small mammal disturbances, we recommend long-term annual monitoring and the application of temporal scaling based on cumulative diversity.