Microbial community composition and network analyses in arid soils of the Patagonian Monte under grazing disturbance reveal an important response of the community to soil particle size

Abstract

The effects of livestock grazing on soil microbial communities are not fully understood in arid regions, where water limitations can have significant consequences on soil health and biological processes. Neither are understood the effects of livestock grazing on the interactions among members of the microbial communities. Here, we used high-throughput amplicon sequencing and co-occurrence network analyses to study changes in microbial community composition and networks in soil from plant-patches and inter-patches under sheep grazed and non-grazed conditions within an arid region of Patagonia. In addition, we analyzed soil and vegetation properties that could be influencing the observed microbial patterns. We detected over 2,000 amplicon sequence variants (ASVs) in soils from plant-patches and a similar number in inter-patches, which abundance shifted between the non-grazed and the grazed sites. Among them, members of the Actinomycetales, Solirubrobacterales, Pedosphaerales and Rhizobiales were present. We further found that connections among them in the network analysis were significantly affected by soil texture. Moreover, soil particle size explained between 24.7% and 31.9% of the variance in microbial community composition. Positive network connections increased from 57.8% in the non-grazed site to 88.6% in the grazed site. This may suggest either an increase in cooperative associations within the community, as a strategy to survive under the stressful conditions imposed by grazing, or a selection of microorganisms with similar niche requirements. We further concluded that members of the Actinomycetales and Rhizobiales seem to have a keystone role in the soil communities from this arid ecosystem.