Precipitation-dependent effects of fencing on foliar fungal diseases in grasslands

Plant diseases are ubiquitous in nature and influenced by large herbivores. Fencing is a widely used management strategy and is employed to exclude large herbivores in efforts to restore overgrazed grasslands. However, how fencing affects foliar fungal diseases and whether the effect is climate-dependent remains unclear. Here, we conducted a multi-site experiment across 19 grasslands in China under different climatic conditions to explore the effects of fencing on foliar fungal diseases (i.e., pathogen load) at the community level. We found that fencing increased pathogen load and that this effect was precipitation-dependent and more pronounced in humid areas. In areas with high precipitation, fencing promoted diseases through both pathogen (pathogen spillover) and plant (increased biomass) pathways. We provide empirical evidence of precipitation-dependent plant-pathogen-herbivore interactions at the interface of community and disease ecology. Our study has important application implications for grassland disease management, underscores the need for the development of sound livestock management guidelines from a geographic perspective, and suggests that moderate grazing in humid areas can reduce grassland disease.