The spatial scale dependence of diazotrophic and bacterial community assembly in paddy soil

Abstract

Aim The factors driving microbial community β‐diversity (variation in composition) at different spatial scales yield fundamental insights into the mechanisms that maintain ecosystem biodiversity, which as yet are uncertain. Here, we explore whether spatial scale‐dependent patterns of β‐diversity vary between microbial functional groups and bacterial taxa (i.e., diazotrophic and bacterial communities) across local to regional scales (from metres to hundreds of kilometres). Location Eastern China. Time period October and November 2015. Major taxa studied Diazotrophic and bacterial communities. MethodsWe use two complementary statistical tools to unveil biotic mechanisms (i.e., species association) underlying variation in β‐diversity of diazotrophic and bacterial communities. We examined distance–decay slopes of both communities at the local (1–113 m), meso‐ (3.4–39 km) and regional (103–668 km) scales. We used an environmentally constrained checkerboard score and topological features of association networks as indices of species association. We then calculated contributions of species association, abiotic factors and geographical distance to explain community β‐diversity. The scale‐dependent distance–decay relationships were also examined in ubiquitous (high occupancy across samples) and endemic communities of diazotrophs and bacteria. ResultsDiazotrophs displayed steeper distance–decay slopes than bacteria, suggesting that the β‐diversity of diazotrophic communities was more variable. The distance–decay slopes were dependent on spatial scales in both communities, owing to different contributions of geographical distance, abiotic factors and species association at three spatial scales. Intriguingly, species association was greater and contributed more to community β‐diversity than other forces at the local scale, implying that species association could greatly alter community structures. Main conclusionsDrivers of diazotrophic and bacterial community β‐diversity depended on spatial scales, resulting in different distance–decay patterns. Moreover, this was the first study to use two methods to demonstrate that species association played important, but as yet unrecognized, roles in driving spatial scale‐dependent β‐diversity.

Broad‐scale distribution of diazotrophic communities is driven more by aridity index and temperature than by soil properties across various forests

“…Alphaproteobacteria was the most abundant class found in forest soils, as has already been observed in other terrestrial ecosystems (Collavino et al, 2014; Gao et al, 2019). A previous study found that Cyanobacteria (10%) was the second most frequent N‐fixer in global soils (Gaby & Buckley, 2011).…”

“…For example, Feng et al (2018) reported that soil pH played a major role in diazotrophic diversity and structure in farmlands. Gao et al (2019) found that soil pH was the most important abiotic factor that contributed to the variation of diazotrophic community β‐diversity in paddy soils at local and regional scales, followed by soil ammonium content and dissolved organic carbon. Shay et al (2015) observed that shifts in diazotrophic communities were best explained by pH in Douglas‐fir forests.…”

Continental-Scale Paddy Soil Bacterial Community Structure, Function and Biotic Interaction

“…The paddy soil network had a greater modularity and included more mutual exclusion relationships compared with the non-paddy soil network. Continuous ploughing and waterlogged conditions could make this soil habitat more homogeneous, leading to relatively weak niche differentiation [13,32].…”

“…The continental and global biogeography of soil microbes has been investigated previously [5][6][7][8][9][10], providing a wealth of data regarding the association between microbial community dynamics and their habitat preferences [5,7], landscape ecological functions and services [6], and biogeochemistry and plant traits [9,11]. Most of these studies mapped microbial biogeography across natural ecosystems, but the impact of human interference as challenges to the well-established biogeographic patterns in naturaloccurring settings remains understudied [12][13][14]. There also has been con icting data associated with whether the microbial communities assemble through deterministic or stochastic processes [15,16], which can be better informed through a broad scale investigation across multiple eld sites.…”

Revegetation by sowing reduces soil bacterial and fungal diversity

“…However, the large spatial heterogeneity of plant density (42-2,221 stem/m 2 ), plant species richness (3-12 species/m 2 ), and soil moisture (4.03%-16.16%) may conceal the effects of restoration methods on the diversity of fungi and bacteria; thus more replications are needed to decrease the influence of site heterogeneity in the future. Moreover, the driver of the observed heterogeneity in fungal and bacterial diversity may change along time scales(Gao et al, 2019), especially in farmland, thus longterm experiments are needed to evaluate the effects of different restoration methods on the diversity of fungi and bacteria in the soil.…”