Grazing livestock dung promotes soil fungal but not bacterial diversity in grasslands
摘要
Cattle and sheep dung improve soil fungal diversity rather than bacterial diversity. Cattle and sheep dung regulate soil fungi through distinct pathways. Cattle dung can directly impact fungal diversity via live microbiota. Sheep dung shifts fungal diversity via lowering soil C:N ratio.
Livestock grazing strongly influences soil microbial diversity in grasslands, yet the role of dung deposition, particularly differences among livestock species, remains poorly understood. Here, we investigated how cattle and sheep dung influence soil microbial diversity using a field experiment in a temperate meadow steppe combined with a microcosm experiment separating nutrient and microbial effects. Results showed that both cattle and sheep dung deposition significantly increased soil fungal diversity but not bacterial diversity in the first year after dung deposition, with no effect detected in the second year. Cattle dung increased fungal diversity most strongly directly beneath dung pads (0 cm), with the stimulatory effect declining with increasing distance (15 and 30 cm). In contrast, sheep dung produced a relatively uniform response with no significant differences among distances. Structural equation modelling showed that cattle dung had a direct positive effect on fungal diversity, whereas sheep dung influenced fungal diversity mainly through indirect soil pathways. Consistent with this pattern, the microcosm experiment demonstrated that only fresh cattle dung containing live microbiota, but not sterilized dung, increased fungal diversity, indicating that the direct effect of cattle dung is attributable to dung-associated microbiota. Overall, livestock dung functions as both a nutrient hotspot and a microbial inoculum, regulating fungal diversity through biotic and abiotic pathways. Dung inputs generate a short-term microbial and nutrient pulse rather than a persistent driver of soil microbial diversity. Our study provides new insights into how grazing livestock shape belowground biodiversity and nutrient cycling in grassland ecosystems.