Community assemblage of free-living diazotrophs along the elevational gradient of Mount Gongga

Abstract

Mountain systems are unique for studying the responses of species distribution and diversity to environmental changes along elevational gradients. It is well known that free-living diazotrophic microorganisms are important to nitrogen cycling in mountain systems. However, the elevational patterns of free-living diazotrophs and the underlying ecological processes in controlling their turnover along broader gradients are less well documented. Here, we investigated the pattern of diazotrophic diversity along the elevational gradient (1800 m-4100 m) in Mount Gongga of China. The results showed that the α-diversity of diazotrophs did not change with the elevation from 1800 m to 2800 m, but decreased at elevations above 3000 m. Such diversity pattern was driven mainly by soil total carbon, nitrogen, and plant richness. Various diazotrophic taxa showed differential abundance-elevation relationships. Ecological processes determining diazotrophic community assemblage shift along the elevations. Deterministic processes were relatively stronger at both low and high elevations, whereas stochastic processes were stronger at the middle elevation. This study also suggested a strong relationship among aboveground plants and diazotrophs, highlighting their potential interactions, even for free-living diazotrophs.

Patterns and Drivers of nirK -Type and nirS -Type Denitrifier Community Assembly along an Elevation Gradient

“…1 ). Similar patterns have also been reported for the elevational changes of soil bacteria ( 28 ), diazotrophs ( 25 ), and methanotrophs ( 24 ) along the same elevation gradient. Such a pattern of variation may be ascribed to the significant differences in soil properties (such as pH, NO 3 − -N, TC, TN, and conductivity) between low (1,800 to 2,800 m) and high (3,000 to 4,100 m) elevations ( 23 ).…”

“…This study proved that nirK -type and nirS -type denitrifier communities were phylogenetically clustered. Deterministic processes (heterogeneous selection) were dominant in shaping nirK -type and nirS -type communities over the elevation gradient, and similar results have also been observed for soil bacteria ( 23 , 30 ), diazotrophs ( 25 ), and methanotrophs ( 24 ) along the same elevation gradient. Furthermore, heterogeneous selection explained a high fraction of turnover in community composition of nirK -type and nirS -type denitrifiers ( Fig.…”

“…Mountain ecosystems exhibit great changes in climate, plant parameters, and soil properties over short spatial distances, which can be used as analogs to environmental gradients to understand microbial activity, community assembly, and their relationships with environmental factors. Previous studies have revealed that deterministic processes (heterogeneous selection) dominate in the assembly processes of soil microbial communities (including communities of soil bacteria, diazotrophs, and methanotrophs) along a large altitudinal gradient, among which climate, plant, and soil parameters play important roles in shaping microbial communities ( 23 – 25 ). Moreover, along with environmental factors (such as temperature and plant parameters) that covary with elevation and could influence the distribution patterns of soil microbial communities ( 23 , 26 ), geological processes (such as parent rock and weathering) explain additional variation in plant and microbial communities ( 27 ).…”

“…Various elevational biodiversity (species richness) patterns of soil bacterial communities ( 23 , 28 – 30 ) and functional microbial groups, e.g., diazotrophs ( 25 ) and methanotrophs ( 24 ), have been observed, suggesting that microbial diversity patterns along elevation gradients are ecosystem specific and scale dependent. However, previous studies have primarily focused on the changes in elevational biodiversity patterns in terms of species richness ( α -diversity), and the elevational changes in microbial community turnover ( β -diversity) have been much less studied ( 31 ).…”

Large-Scale Characterization of the Soil Microbiome in Ancient Tea Plantations Using High-Throughput 16S rRNA and Internal Transcribed Spacer Amplicon Sequencing

“…Both the single peak pattern (bacteria) and the bimodal pattern (archaebacteria) were observed for the microbial diversity (Singh et al, 2012). The nitrogen-fixing bacteria also showed diverse relationships with altitude (Wang et al, 2019). According to Shen et al (2015), the composition of the bacterial communities at high altitudes is most complex and diverse among all microbes.…”