Continental-scale niche differentiation of dominant topsoil archaea in drylands

Distribution, species richness, and relative importance of different plant life forms across drylands in China

Studies on plant diversity are usually based on the total number of species in a community. However, few studies have examined species richness (SR) of different plant life forms in a community along large-scale environmental gradients. Particularly, the relative importance (RIV) of different plant life forms in a community and how they vary with environmental variables are still unclear. To fill these gaps, we determined plant diversity of ephemeral plants, annual herbs, perennial herbs, and woody plants from 187 sites across drylands in China. The SR patterns of herbaceous plants, especially perennial herbs, and their RIV in plant communities increased with increasing precipitation and soil nutrient content; however, the RIV of annual herbs was not altered along these gradients. The SR and RIV of ephemeral plants were affected mainly by precipitation seasonality. The SR of woody plants had a unimodal relationship with air temperature and exhibited the highest RIV and SR percentage in plant communities under the harshest environments. An obvious shift emerged in plant community composition, SR and their critical impact factors at 238.5 mm of mean annual precipitation (MAP). In mesic regions (> 238.5 mm), herbs were the dominant species, and the SR displayed a relatively slow decreasing rate with increasing aridity, which was mediated mainly by MAP and soil nutrients. In arid regions (< 238.5 mm), woody plants were the dominant species, and the SR displayed a relatively fast decreasing rate with increasing aridity, which was mediated mainly by climate variables, especially precipitation. Our findings highlight the importance of comparative life form studies in community structure and biodiversity, as their responses to gradients differed substantially on a large scale.

Salinity drives niche differentiation of soil bacteria and archaea in Hetao Plain, China

Soil salinization is a critical environmental issue that limits plant productivity and disrupts ecosystem functions. As important indicators of soil environment, soil microbes play essential roles in driving nutrient cycling and sustaining ecosystem services. Therefore, understanding how microbial communities and their functional potentials respond to varying levels of soil salinization across different land use types is crucial for the restoration and management of salt-affected ecosystems. In this study, we randomly selected 63 sites across the Hetao Plain, covering an area of ∼2500 km2. Our results showed that both salinity- and fertility-related soil parameters were significantly correlated with bacterial and archaeal diversities, with soil salinity emerging as the stronger predictor of prokaryotic diversity. Intriguingly, bacterial and archaeal communities were tightly interlinked but displayed opposite trends in response to environmental factors, indicating a clear microbial niche differentiation driven by soil salinity. Moreover, the generalist functions of bacteria and archaea (e.g., chemoheterotrophy) exhibited contrasting responses to environmental parameters, while their specialist functions (e.g., nitrification) responded consistently. These findings highlight the pivotal role of soil salinity in shaping the niche differentiation of bacterial and archaeal communities in saline soils, providing insights to guide salinity-centered restoration strategies for effective marginal land management.

Diversity and Activity of Soil N2O-Reducing Bacteria Shaped by Urbanization

Nitrous oxide (N2O) is a potent greenhouse gas with various production pathways. N2O reductase (N2OR) is the primary N2O sink, but the distribution of its gene clades, typically nosZI and atypically nosZII, along urbanization gradients remains poorly understood. Here we sampled soils from forests, parks, and farmland across eight provinces in eastern China, using high-throughput sequencing to distinguish between two N2O-reducing bacteria clades. A deterministic process mainly determined assemblies of the nosZI communities. Homogeneous selection drove nosZI deterministic processes, and both homogeneous and heterogeneous selection influenced nosZII. This suggests nosZII is more sensitive to environmental changes than nosZI, with significant changes in community structure over time or space. Ecosystems with stronger anthropogenic disturbance, such as urban areas, provide diverse ecological niches for N2O-reducing bacteria (especially nosZII) to adapt to environmental fluctuations. Structural equation modeling (SEM) and correlation analyses revealed that pH significantly influences the community composition of both N2O-reducing bacteria clades. This study underscores urbanization's impact on N2O-reducing bacteria in urban soils, highlighting the importance of nosZII and survival strategies. It offers novel insights into the role of atypical denitrifiers among N2O-reducing bacteria, underscoring their potential ecological importance in mitigating N2O emissions from urban soils.

Interplay between edaphic and climatic factors unravels plant and microbial diversity along an altitudinal gradient

Altitude influences biodiversity and physiochemical soil attributes in terrestrial ecosystems. It is of immense importance to know the patterns of how interactions among climatic and edaphic factors influence plant and microbial diversity in various ecosystems, particularly along the gradients. We hypothesize that altitudinal variation determines the distribution of plant and microbial species as well as their interactions. To test the hypothesis, different sites with variable altitudes were selected. Analyses of edaphic factors revealed significant (p < 0.001) effects of the altitude. Soil ammonium and nitrate were strongly affected by it contrary to potassium (K), soil organic matter and carbon. The response patterns of individual taxonomic groups differed across the altitudinal gradient. Plant species and soil fungal diversity increased with increasing altitude, while soil archaeal and bacterial diversity decreased with increasing altitude. Plant species richness showed significant positive and negative interactions with edaphic and climatic factors. Fungal species richness was also significantly influenced by the soil ammonium, nitrate, available phosphorus, available potassium, electrical conductivity, and the pH of the soil, but showed non-significant interactions with other edaphic factors. Similarly, soil variables had limited impact on soil bacterial and archaeal species richness along the altitude gradient. Proteobacteria, Ascomycota, and Thaumarchaeota dominate soil bacterial, fungal, and archaeal communities, with relative abundance of 27.4%, 70.56%, and 81.55%, respectively. Additionally, Cynodon dactylon is most abundant plant species, comprising 22.33% of the recorded plant taxa in various study sites. RDA revealed that these communities influenced by certain edaphic and climatic factors, e.g., Actinobacteria strongly respond to MAT, EC, and C/N ratio, Ascomycota and Basidiomycota show strong associations with EC and MAP, respectively. Thaumarcheota are linked to pH, and OM, while Cyperus rotundus are sensitive to AI and EC. In conclusion, the observed variations in microbial as well as plant species richness and changes in soil properties at different elevations provide valuable insights into the factors determining ecosystem stability and multifunctionality in different regions.

Species composition of root-associated mycobiome of ruderal invasive Anthemis cotula L. varies with elevation in Kashmir Himalaya

Investigating the microbial communities associated with invasive plant species can provide insights into how these species establish and thrive in new environments. Here, we explored the fungal species associated with the roots of the invasive species Anthemis cotula L. at 12 sites with varying elevations in the Kashmir Himalaya. Illumina MiSeq platform was used to identify the species composition, diversity, and guild structure of these root-associated fungi. The study found a total of 706 fungal operational taxonomic units (OTUs) belonging to 8 phyla, 20 classes, 53 orders, 109 families, and 160 genera associated with roots of A. cotula, with the most common genus being Funneliformis. Arbuscular mycorrhizal fungi (AMF) constituted the largest guild at higher elevations. The study also revealed that out of the 12 OTUs comprising the core mycobiome, 4 OTUs constituted the stable component while the remaining 8 OTUs comprised the dynamic component. While α-diversity did not vary across sites, significant variation was noted in β-diversity. The study confirmed the facilitative role of the microbiome through a greenhouse trial in which a significant effect of soil microbiome on height, shoot biomass, root biomass, number of flower heads, and internal CO2 concentration of the host plant was observed. The study indicates that diverse fungal mutualists get associated with this invasive alien species even in nutrient-rich ruderal habitats and may be contributing to its spread into higher elevations. This study highlights the importance of understanding the role of root-associated fungi in invasion dynamics and the potential use of mycobiome management strategies to control invasive species.

Effect of Biochar on Rhizosphere Soil Microbial Diversity and Metabolism in Tobacco-Growing Soil

In this study, four different biochar application rates and a control were set up using indoor potted tobacco, to study the effects of biochar on the microbial diversity and metabolism of tobacco-growing soil. The five treatments were as follows: control—0% biochar (w/w) + 26 g fertilizer/pot; biochar treatments—1% biochar (w/w) + 26 g fertilizer/pot, 2% biochar (w/w) + 26 g fertilizer/pot, 3% biochar (w/w) + 26 g fertilizer/pot, and 4% biochar (w/w) + 26 g fertilizer/pot. We found that biochar increases the microbial diversity of soils and simultaneously changes the microbial community structure. Under the influence of biochar, soil urease activity increased by 18%, invertase activity increased by 23.40%, polyphenol oxidase activity increased by 59.50%, and catalase activity increased by 30.92%. Biochar also significantly increased the microbial biomass carbon and nitrogen content of the soil. Soil microbial biomass nitrogen had a positive correlation on bacterial diversity, with the highest coefficient, while soil microbial biomass carbon had a positive correlation on fungal diversity, with the highest coefficient. The microbial diversity and metabolic capacity of soil are improved under the influence of biochar, and soil enzyme activity and microbial biomass carbon and nitrogen have positive impacts on soil microbial diversity.