Summary Sediment microbial communities in arid inland rivers are important for biogeochemical cycling, but the assembly mechanisms and network responses across the transition from irrigated oases to desert margins remain unclear. We investigated bacterial and fungal communities in Yarkand River sediments along salinity and nutrient gradients using 16S rRNA and ITS sequencing, sediment chemistry, iCAMP null-model analysis, and co-occurrence networks. Downstream increases in electrical conductivity, total nitrogen, and pH were associated with reduced bacterial α-diversity and turnover from nutrient-responsive Pseudomonadota in the oasis midstream to stress-tolerant Chloroflexota and Actinomycetota in the desert downstream. Fungal diversity showed high inter-site variability without a linear decline. Despite strong physicochemical gradients, ecological drift dominated assembly in both kingdoms, while desert networks showed higher connectivity. These findings support a hierarchical assembly model in which salinity filters community composition, but stochastic processes and network densification shape benthic microbiota in arid river sediments.
Soil nutrient transformation capacity is a critical determinant of sustainable productivity in perennial cropping systems; however, the extent to which high-yielding crops actively regulate rhizosphere microbial assembly to maintain nutrient availability remains poorly understood. We investigated whether root exudates from high-yielding alfalfa (Medicago sativa L.) selectively recruit plant growth-promoting rhizobacteria (PGPR) to enhance nutrient transformation. In an 8-year continuous alfalfa system (2018-2025), high-yielding cultivars increased soil organic carbon by 8.64%, total nitrogen by 6.01%, and moderately labile phosphorus fractions by 1.62%. Rhizobox experiments demonstrated that root exudates enhanced growth only with an active microbiome. High-yielding alfalfa enriched PGPR communities, specifically Ensifer, Pseudomonas, and Bacillus. Isolated strains exhibited N fixation, P solubilisation, and IAA production. Metabolomic profiling revealed that exudates were enriched in specific sugars and amino acids. Maltopentaose, maltotetraose, taurine, N-acetyl-L-leucine, and asparagine functioned as chemoattractants, stimulating PGPR proliferation and biofilm formation. These findings demonstrate that root exudate-mediated, targeted recruitment of functional PGPR enhances N fixation and P transformation, thereby supporting sustained high alfalfa productivity. This study demonstrates a key rhizosphere mechanism underlying the long-term sustainability of high-yielding perennial legume systems and provides a mechanistic basis for microbiome-informed sustainable alfalfa production and management.
Yanliang Sun, Kongqin Wei, Kaixin Yang et al.· Plant, Cell and Environment· 0 citations
Combined stress more strongly inhibited plant height, stem diameter, fresh weight, net photosynthetic rate, and transpiration rate than single stresses, and insights into alfalfa adaptation to multiple abiotic stresses are provided.
Lihe Su, Yong-Cheng Chen, Xudong Zhang et al.· Journal of Agricultural and...· 0 citations
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