Soil microbial community structure is unaltered by grazing intensity and plant species richness in a temperate grassland steppe in northern China

Authors: RONG, YUPING - China Agricultural University; Monaco, Thomas; LIU, Z - Hebei Academy Of Agriculture & Forestry; ZHAO, M - Inner Mongolian Agriculture University; HAN, G - Inner Mongolian Agriculture University

Submitted to: European Journal of Soil Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2022
Publication Date: 4/8/2022
Citation: Rong, Y., Monaco, T.A., Liu, Z., Zhao, M., Han, G. 2022. Soil microbial community structure is unaltered by grazing intensity and plant species richness in a temperate grassland steppe in northern China. European Journal of Soil Biology. 110. Article 103404. https://doi.org/10.1016/j.ejsobi.2022.103404.
DOI: https://doi.org/10.1016/j.ejsobi.2022.103404

Interpretive Summary: Livestock grazing has led to grassland degradation in many semiarid regions of the world. Less is known about how grazing intensity may influence soil microbial communities. We conducted a five year study in northern China to evaluate how grazing intensity at four levels influence bacterial and fungal community structure. In addition, the influence of grazing intensity was considered in distinct vegetation patch-types including low plant diversity, high plant diversity, and dominant species patches. While grazing significantly reduced microbial biomass, as expected, the influence of grazing intensity was rarely significant, and often varies across patch types. In addition, soil properties, including soil pH and nitrate concentration, were closely associated with the changes in microbial communities. Overall, we conclude that variable grazing intensity has little influence on microbial community stability.

Technical Abstract: Grazing intensity influences the productivity and sustainability of grassland systems through modifying aboveground biomass soil microbes, and nutrient dynamics. Although heavy grazing is a key factor associated with grassland degradation in China and alleviating grazing intensity can assist grassland vegetation restoration, the influence of variable grazing intensity on belowground process is less understood. We examined the effects of four grazing intensities (0, 1.00, 1.43 and 2.33 sheep-units ha-1 year-1) applied during five growing seasons on soil microbial biomass and community structure of a grassland ecosystem in Hebei Province, China. Within each grazing intensity, vegetation and soil were sampled in patches with low and high diversity and in patches composed of the dominant species (i.e., Leymus chinenis [Trin.], Tzvel. and Carex duriuscula C. A. Mey.). Grazing significantly (P<0.05) decreased soil microbial biomass and increased the ratio of bacterial-to-fungal biomass relative to the non-grazed control, but differences were not significant among the grazing intensities. In addition, principal components analysis revealed that grazing intensity explained 25.42% and 54.53% of the variation among bacterial and fungi communities, respectively. Grazing, regardless of intensity, also resulted in a bacterial communities distinct from the non-grazed control. Redundancy analysis also revealed that while soil pH and organic carbon had the strongest influence on bacterial community structure, soil electrical conductivity and NO3--N primarily influenced fungi community structure. Collectively our results indicate that mirobial communities in semi-arid grasslands can remain structurally stable even when subjected to persistent environmental change imposed by grazing pressure.