Rapid responses of the soil microbiome to experimental dung depositions in grassland ecosystem

Grazing is the most extensive land use in drylands worldwide, wherein the soil microbiome is known to support multiple ecosystem functions. Yet, the experimental influence of livestock grazing and their dung deposits on the soil microbiome remains poorly understood. We compared the short term impact of sheep dung depositions on the soil bacterial and fungal microbiome of two grasslands: non degraded and over-grazed, in northern China. Sheep dung additions resulted in rapid effects on the soil fungal community in the already overgrazed grassland, but it had a limited effect on the non-degraded grassland. Sheep dung declined fungal Shannon index and network complexity in the degraded grassland. In the case of bacteria, sheep dungs decreased the Chao1 and bacterial diversity in the non-degraded and degraded grassland, and reduced bacteria community rare taxa network complexity. However, sheep dungs did not alter the relative abundance and community composition of bacterial dominant phyla either in the non-degraded or in the overgrazed grassland. Short term experimental applications of sheep dung had a rapid reduced effect on the soil microbial diversity of two grasslands especially in degraded grassland. This knowledge is critical to provide guidelines for managers to support the conservation of the soil microbiome in grasslands subjected to grazing, and provide new experimental evidences of the impacts of grazing on the soil microbiome.