Search

Degraded grassland can be restored through management practices such as fencing to protect land from overgrazing. However, little is known about the dynamics of underground microbial communities and their associated ecological function during the restoration process. In this study, we investigated changes in the soil bacterial community composition with varying restoration time in the Leymus chinensis steppe. We also studied the differences in the soil bacterial community composition between a Leymus chinensis steppe and a Stipa grandis steppe at the same restoration time in the Inner Mongolia of China. Results showed that restoration of the degraded steppe through fencing significantly changed the bacterial community composition through the restoration time. The relative abundances of Chloroflexi and Cyanobacteria decreased significantly with restoration. However, the relative abundances of copiotrophic Proteobacteria and Bacteriodetes increased. Significant changes for many dominant taxa occurred between 7 and 13 years of restoration time in the Leymus chinensis steppe. Shifts in the composition of bacterial communities with fencing and grazing were driven by multiple factors, including soil moisture, pH, nutrients (organic carbon and nitrogen, etc.). Network analysis of soil bacterial community compositions showed that the three largest modules in co-occurrence networks were separated by fencing, grazing and steppe type. This study revealed the successions of underground microbial communities associated with steppe restoration management over time.

Understanding the differentiation of soil bacterial communities under precipitation and temperature gradients is crucial for assessing the impacts of environmental filters on ecosystem structure and function. Here we investigated spatial variations of bacterial communities along a precipitation and temperature transect in the eastern Inner Mongolia steppe, China. The aims are to understand the biogeographic pattern and key drivers shaping soil bacterial communities along the transect. Our results showed that the soil bacterial community along the 451-km transect exhibited the distance-decay relationship, decreasing in community similarity with geographic distance. Obvious changes in the bacterial community structure occurred at an annual precipitation from 215 to 261 mm, which was close to the boundary between arid and semi-arid systems. The relative abundances of Proteobacteria, Bacteroidetes, and Acidobacteria increased with precipitation, while those of Actinobacteria, Chloroflexi, and Gemmatimonadetes decreased. Environmental filtering was observed to be the key in shaping bacterial biogeographic patterns, and climate conditions exert indirect effects on soil bacterial communities mainly through direct effects on soil properties. Soil pH and plant coverage were important to soil bacterial communities in both arid and semi-arid steppes. Our findings provided insights for understanding the linkages among geographic distance, environmental filters, and soil bacterial communities in Eurasian steppe ecosystems.

Methane oxidation driven by aerobic methanotrophs plays a critical role in the alleviation of global warming. Yet, we still know little about the assembly mechanisms of methanotrophic communities and the corresponding drivers in mountain soils. Here, we comprehensively investigated methanotrophic bacteria along an elevational gradient (1800–4100 m) in Mount Gongga, China. Our results indicated that previously unrecognized AOB-rel methanotrophs predominated in mountain forest soils, and they showed distinct phylogenetic differentiation and pH preferences (pH 5.9–7.2 and pH 4.7–5.6 for AOB-rel subclade 1 and 2, respectively). Soil pH, temperature and precipitation primarily shaped methanotrophic communities. The community assembly of aerobic methanotrophs was governed mainly by deterministic processes. Our findings also implied that more acidic soils contained less phylogenetically clustered methanotrophic communities, and more neutral soils harbored more phylogenetically clustered communities. This study is the first to illustrate the significant role of soil pH in the assembly of aerobic methanotrophic communities and reinforce the importance of AOB-rel methanotrophs in atmospheric methane oxidation process in mountain forest soils.

Assembly mechanisms and responses of diazotrophic habitat specialists, opportunists, and generalists may differ among various steppe ecosystems. In this study, we investigated the ecological processes that determine the assemblies of diazotrophic communities in meadows and typical steppes (MT), desert steppes (D), and sandy steppes (S) and the effects of habitat environments on diazotrophic specialists, opportunists, and generalists in Inner Mongolia, China. The results showed that taxonomic and phylogenetic communities of diazotrophs were clustered according to their habitat types, as community dissimilarities among habitat types were significantly higher than those within them. Variable selection and dispersal limitation were recognized as the dominant ecological processes that shape diazotrophic community assemblages. Furthermore, the diazotrophic populations were dichotomized into specialists, opportunists and generalists with various strategies to adapt to habitat types. The richness of specialists significantly correlated with vegetation variables, implying that specialists have greater responses to vegetation than generalists and opportunists. This study provides insights into the mechanisms of diazotrophic community differentiation when habitat environments change.