Effects of grazing on soil nutrients and microbial community of Pinus sylvestris var. mongolica forest in sandy land

: A grazing and enclosed Pinus sylvestris var. mongolica forests in sandy land was selected to explore the effects of grazing on soil nutrients and microbial communities. The microbial community composition and diversity between grazing and enclosed soil was determined using high-throughput sequencing technology. Soil chemical indexes were determined for estimating variation in the nutrients. The results showed that total phosphorus content decreased significantly after grazing ( P < 0.05). Soil organic carbon and total nitrogen content also decreased, while ammonium nitrogen, nitrate nitrogen, and available phosphorus increased, but the change was not significant ( P > 0.05). The grazing and enclosed plots showed 17.1% - 24.6% similarity in the soil microbial community composition and the OTUs of fungi and bacteria were lower in grazing than enclosed plots. At each classification level, the number of fungi and bacteria in grazing plots was less than that in enclosed plots. Results showed grazing significantly reduced the number of bacteria at the genus level( P < 0.05). The proportion of basidiomycetes in grazing was significantly lower than that in enclosure ( P < 0.05). No significant indigenous effect on bacterial phylum level ( P > 0.05) was observed. In terms of soil microbial diversity, grazing significantly reduced the Chao1 index and Shannon index of bacteria ( P < 0.01), and had no significant effect on fungal community diversity ( P > 0.05). The effect of grazing on soil bacterial diversity index was greater than that of fungi. In summary, grazing in the Pinus sylvestris var. mongolica forest in sandy land has different degrees of negative impacts on soil nutrients and soil microorganisms. Therefore, the grazing should be moderately reduced in this region to alleviate land pressure and ensure the sustainable utilization of the Pinus sylvestris var.