Distinct Assembly Processes and Determinants of Soil Microbial Communities between Farmland and Grassland in Arid and Semiarid Areas

Abstract

It is critical to identify the assembly processes and determinants of soil microbial communities to better predict soil microbial responses to environmental change in arid and semiarid areas. Here, soils from 16 grassland-only, 9 paired grassland and farmland, and 16 farmland-only sites were collected across the central Inner Mongolia Plateau covering a steep environmental gradient. Through analyzing the paired samples, we discovered that land uses had strong effects on soil microbial communities, but weak effects on their assembly processes. For all samples, although no environmental variables were significantly correlated with the net relatedness index (NRI), both the nearest taxon index (NTI) and the β-nearest taxon index (βNTI) were most related to mean annual precipitation (MAP). With the increase of MAP, soil microbial taxa at the tips of the phylogenetic tree were more clustered, and the contribution of determinism increased. Determinism (48.6%), especially variable selection (46.3%), and stochasticity (51.4%) were almost equal in farmland, while stochasticity (75.0%) was dominant in grassland. Additionally, Mantel tests and redundancy analyses (RDA) revealed that the main determinants of soil microbial community structure were MAP in grassland, but mean annual temperature (MAT) in farmland. MAP and MAT were also good predictors of the community composition (the top 200 dominant OTUs) in grassland and farmland, respectively. Collectively, in arid and semiarid areas, soil microbial communities were more sensitive to environmental change in farmland than in grassland, and unlike the major impact of MAP on grassland microbial communities, MAT was the primary driver of farmland microbial communities. Importance As one of the most diverse organisms, soil microbes play indispensable roles in many ecological processes in arid and semiarid areas with limited macrofaunal and plant diversity, yet the mechanisms underpinning soil microbial community are not fully understood. In this study, soil microbial communities were investigated along a 500 km transect covering a steep environmental gradient across farmland and grassland in the areas. The results showed that precipitation was the main factor mediating the assembly processes. Determinism was more influential in farmland, and variable selection of farmland was twice that of grassland. Temperature mainly drove farmland microbial communities, while precipitation mainly affected grassland microbial communities. These findings provide new information about the assembly processes and determinants of soil microbial communities in arid and semiarid areas, consequently improving the predictability of the community dynamics, which have implications for sustaining soil microbial diversity and ecosystem functioning, particularly under global climate change conditions.

Plant selection and ecological microhabitat drive domestications of shrub-associated microbiomes in a revegetated shrub ecosystem

“…6b), indicating that bacteria across six microhabitats had more similar composition (Hanson et al, 2012; Su et al, 2020). Compared to bacterial communities, fungi communities at multiple microhabitats are predominantly govern by dispersal limitation (Bonito et al 2014; Richter-Heitmann et al, 2020; Xu et al, 2021). Our results supported this view, the proportion of dispersal limitation in fungi at all microhabitats was higher than that in bacteria (Figure.…”

“…Shrubs are foundation species in fragile dryland ecosystems and performs diverse ecological functions, such as maintaining species diversity, controlling soil erosion, and promoting soil formation (Maestre et al, 2021). Each plant taxon harbours a characteristic mixture of microorganisms, collectively termed as the ‘plant microbiota’ (Xu et al, 2021; Vandenkoornhuyse et al, 2015). These plant-specific microbiomes impact the nutrition and water acquisition of xeric plants, suppress diseases, and support plant health and resistance to harsh environments (i.e., drought, salt, and high temperature) (Cordovez et al, 2019; Trivedi et al, 2020); thereby, driving plant-soil feedbacks (Delgado-Baquerizo et al, 2020).…”

“…Several studies have demonstrated that plant-associated microbial composition and functions are regulated by plant host genotype (Beckers et al, 2017; Soussi et al, 2016; Vandenkoornhuyse et al, 2015), i.e., each plant habitat harbours its own characteristic microbiome (Cordovez et al, 2019). Moreover, host plants can provide a number of habitats for microorganisms and then subtly affect microbiomes that confer tolerance to abiotic stress by supplying photosynthetic carbon (Müller et al, 2016; Xu et al, 2021). For example, root exudate and rhizodeposition predominantly influence the rhizosphere microbiota (Gupta et al, 2021; Zhalnina et al, 2018).…”

“…Recently, niche differentiation of plant-associated microbial taxa, mainly at the soil-root interface (rhizosphere and root endosphere), has received great research attention (Trivedi et al, 2019; Xiong et al, 2021a; Wang et al, 2022). In fact, each plant tissue (fruits, seeds, flowers, leaves, stems, and roots) and soil habitat (rhizosphere and litter) provide unique ecological niche that supports a characteristic microbial community (Gupta et al, 2021; Vandenkoornhuyse et al, 2015; Xu et al, 2021). Potentially, different microhabitats reflect different biotic (substrate and organic matter) and abiotic (temperature and water availability) conditions (Müller et al, 2016; Zheng and Gong., 2019).…”

“…have specific microbiota members, they have a part of similar functional diversities (Bai et al, 2015). Whether microbial functional overlap is attributed to the migration of microorganisms among the different compartments, and whether these compartment microbiome assemblies are mainly influenced by the soil microbiome, remain to be elucidated (Turner et al, 2013; Xu et al, 2021). Therefore, clarifying the diversity, abundance, composition, and dynamics of each microhabitat is helpful for improving the understanding of plant-environment interactions (Bulgarelli et al, 2012).…”