The alpine meadow ecosystem, as the main ecosystem of the Qinghai-Tibet Plateau, has been heavily degraded over the past several decades due to overgrazing and climate change. Although soil microorganisms play key roles in the stability and succession of grassland ecosystems, their response to grassland degradation has not been investigated at spatial scale. Here, we systematically analyzed the spatial turnover rates of soil prokaryotic and fungal communities in degraded and undegraded meadows through distance-decay relationship (DDR) and species area relationship (SAR), as well as the community assembly mechanisms behind. Although the composition and structure of both fungal and prokaryotic communities showed significant changes between undegraded and degraded meadows, the steeper spatial turnover rates were only observed in fungi. Mantel tests indicated that edaphic variables and vegetation factors showed significant correlations to the fungal community only in degraded meadow, suggesting soil and vegetation heterogeneity contributed to the steeper spatial scaling pattern. Correspondingly, a novel phylogenetic null model analysis (iCAMP) demonstrated that environmental selection was enhanced in the fungal community assembly process during meadow degradation. Interestingly, dispersal limitation was also enhanced for the fungal community in the degraded meadow, and its relative percentages showed a significant linear increase with the spatial distance, suggesting that dispersal limitation played a greater role as distance increased. Our findings indicated the spatial scaling of the fungal community is altered during meadow degradation by both niche selection and dispersal limitation. This study provides a new perspective for the assessment of soil microbial responses to vegetation changes in alpine areas.

Bathyarchaeia (formerly Bathyarchaeota) is a group of highly abundant archaeal communities that play important roles in global biogeochemical cycling. The presence of Bathyarchaeia in arable soils is relatively limited. In this study, we aimed to investigate the spatial distributions and diversity of Bathyarchaeia in paddy soils across eastern China, which is a major rice production region. The relative abundance of Bathyarchaeia among total archaea ranged from 3% to 68%, and Bathy-6 was the dominant subgroup. Bathyarchaeia showed higher migration ability and wider niche. Soil pH and C/N ratio were identified as key factors influencing the Bathyarchaeia composition, whereas C/N ratio and mean annual temperature influenced the relative abundance of Bathyarchaeia. Network analysis showed that specific Bathyarchaeia taxa occupied keystone positions in the archaeal community and co-occurred with some methanogenic and ammonia-oxidizing archaea. This study provides important insights into the biogeography and niche differentiation of Bathyarchaeia in agroecosystems.

Soil microbial diversity distribution patterns and their ecological linkage with aboveground plant diversity are essential for both theoretical and applied ecology. However, a number of studies have shown soil microbial distribution patterns along different environmental gradients are inconsistent and their ecological linkages with plant diversity haven’t been well clarified. In this study, the plant and soil microbial diversity was simultaneously surveyed in 30 natural broadleaved forest sites along a 2500 km latitudinal gradient (18°–40°N) in China. The soil bacterial and fungal diversity was detected using the Illumina sequencing technique. The results showed soil bacterial and fungal community structure differed significantly among different sites and their alpha -diversity significantly increased as latitudinal increased (P < 0.001), and the plant and soil microbial beta-diversity was significantly linkages (P < 0.001). Based on the partial Mantel test, boosted regression tree and structural equation model analysis, we found plant alpha-diversity had no positive correlation with soil microbial alpha-diversity, and soil pH and climate condition (including mean annual precipitation and mean annual temperature) were the most important factors affecting soil microbial community structure. However, soil microbial heterogeneity might significantly affect aboveground plant community structure. Our analysis indicated that the plant beta-diversity could predict soil microbial beta-diversity at regional forest system, and soil pH plays higher roles than plant diversity in affecting soil microbial community at regional scale. This study provides new insights into the soil microbial diversity distribution patterns and ecological linkage between plant diversity and soil microbial diversity in natural forest ecosystem at the regional scale.

In river sediments, nitrate is a more preferable electron sink for microbial respiration than oxygen, for its good solubility and high redox potential. Nitrate amendment has been used to accelerate oxidation of pollutants but very few studies focused on microbial dynamics during bioremediation. Here we simulated a nitrate surge and monitored the microbial responses in a sulfide-rich river sediment. Original communities were found dominated by methanogens and syntrophic bacteria, yet nitrate input enriched two chemolithotrophic denitrifiersThiobacillus and Luteimonas , in spite of abundant organic carbons there. This led to simplified community composition, function and interactive networks. Similarly, serial dilutions of sediments found that Thiobacillus thiophilu s dominated 18/30 communities because of its simultaneous nitrate reduction and sulfide oxidation. Interestingly, syntrophic bacteria and archaea performing interspecies cross-feeding rather than the dominant denitrifiers were sustaining microbial interactions. Therefore, environment perturbations that inhibit native auxotrophs will very likely disrupt original microbial interactions.