Streptomyces tabacisoli sp. nov, isolated from the rhizosphere soil of Nicotiana tabacum
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The mechanism effects of root exudate on microbial community of rhizosphere soil of tree, shrub, and grass in forest ecosystem under N deposition
Forests are composed of various plant species, and rhizosphere soil microbes are driven by root exudates. However, the interplay between root exudates, microbial communities in the rhizosphere soil of canopy trees, understory shrubs, grasses, and their responses to nitrogen (N) deposition remains unclear. Pinus tabulaeformis, Rosa xanthina, and Carex lancifolia were used to investigate root exudates, rhizosphere soil microbial communities, and their responses to N application in forest ecosystem. Root exudate abundances of P. tabulaeformis were significantly higher than that of R. xanthina and C. lancifolia, with carbohydrates dominating P. tabulaeformis and R. xanthina root exudates, fatty acids prevailing in C. lancifolia root exudates. Following N application, root exudate abundances of P. tabulaeformis and R. xanthina initially increased before decreasing, whereas those of C. lancifolia decreased. Microbial number of rhizosphere soil of C. lancifolia was higher than that of P. tabulaeformis and R. xanthina, but there was insignificant variation of rhizosphere soil microbial diversity among plant species. N application exerted promotional and inhibitory impacts on bacterial and fungal numbers, respectively, while bacterial and fungal diversities were increased by N application. Overall, N application had negative effects on root exudates of P. tabulaeformis, inhibiting rhizosphere soil microbial populations. N application suppressed rhizosphere soil microbial populations by increasing root exudates of R. xanthina. Conversely, N application elevated nutrient content in the rhizosphere soil of C. lancifolia, reducing root exudates and minimally promoting microbial populations. This study highlights the importance of understory vegetation in shaping soil microbial communities within forests under N deposition.
Tomato growth stage modulates bacterial communities across different soil aggregate sizes and disease levels
Soil aggregates contain distinct physio-chemical properties across different size classes. These differences in micro-habitats support varied microbial communities and modulate the effect of plant on microbiome, which affect soil functions such as disease suppression. However, little is known about how the residents of different soil aggregate size classes are impacted by plants throughout their growth stages. Here, we examined how tomato plants impact soil aggregation and bacterial communities within different soil aggregate size classes. Moreover, we investigated whether aggregate size impacts the distribution of soil pathogen and their potential inhibitors. We collected samples from different tomato growth stages: before-planting, seedling, flowering, and fruiting stage. We measured bacterial density, community composition, and pathogen abundance using qPCR and 16 S rRNA gene sequencing. We found the development of tomato growth stages negatively impacted root-adhering soil aggregation, with a gradual decrease of large macro-aggregates (1–2 mm) and an increase of micro-aggregates (<0.25 mm). Additionally, changes in bacterial density and community composition varied across soil aggregate size classes. Furthermore, the pathogen exhibited a preference to micro-aggregates, while macro-aggregates hold a higher abundance of potential pathogen-inhibiting taxa and predicted antibiotic-associated genes. Our results indicate that the impacts of tomatoes on soil differ for different soil aggregate size classes throughout different plant growth stages, and plant pathogens and their potential inhibitors have different habitats within soil aggregate size classes. These findings highlight the importance of fine-scale heterogeneity of soil aggregate size classes in research on microbial ecology and agricultural sustainability, further research focuses on soil aggregates level could help identify candidate tax involved in suppressing pathogens in the virtual micro-habitats.
Metabolite-driven mechanisms reveal chemical ecology of Lehmann Lovegrass (Eragrostis lehmanniana) invasion in North American semi-arid ecosystems
Invasive plants threaten global ecosystems, yet traditional analyses of functional traits cannot fully explain their dominance over co-occurring natives. Metabolomics offers insights into plant invasions, but single-technique studies often miss critical biochemical mechanisms. We employ a multimodal metabolomics approach (¹H NMR, LC MS/MS, FT-ICR-MS, and MALDI-MSI) to investigate the biochemical basis of Lehmann lovegrass (Eragrostis lehmanniana) invasion in semi-arid North America, comparing it with a co-occurring native grass, Arizona cottontop (Digitaria californica). Our analysis reveals three metabolomic traits of Lehmann lovegrass compared to Arizona cottontop: Enhanced nitrogen allocation in shoots, reduced defensive metabolites in root layers; and increased root exudate modulation under stress conditions. These traits suggest Lehmann lovegrass succeeds through adaptation to increasing aridity rather than direct competition, demonstrating adaptation to nutrient-poor environments and high phenotypic plasticity in response to increasing aridity. This integrated metabolomic approach provides new mechanistic insights into invasion ecology and plant adaptation under environmental change.
Crop rotation increases Tibetan barley yield and soil quality on the Tibetan Plateau
Tibetan barley (Hordeum vulgare) accounts for over 70% of the total food production in the Tibetan Plateau. However, continuous cropping of Tibetan barley causes soil degradation, reduces soil quality and causes yield decline. Here we explore the benefits of crop rotation with wheat and rape to improve crop yield and soil quality. We conducted 39 field experiments on the Tibetan Plateau, comparing short-term (≤5 years), 5–10 years and long-term (≥10 years) continuous cropping with rotation of Tibetan barley with wheat or rape. Results showed that Tibetan barley–wheat and Tibetan barley–rape rotations increased yields by 17% and 12%, respectively, while improving the soil quality index by 11% and 21%, compared with long-term continuous cropping. Both Tibetan barley rotations with wheat and rape improved soil quality and consequently yield, mainly by increasing soil microbial biomass nitrogen and microbial biomass carbon and decreasing pH. By contrast, long-term continuous cropping led to decreased soil organic matter, lower microbial biomass nitrogen and increased pH, contributing to yield decline. The benefits of rotations on crop yield and soil quality increased over time. Implementing crop rotation with wheat or rape thus offers a sustainable agricultural strategy for improving food security on the Tibetan Plateau.
Higher temperature sensitivity of forest soil methane oxidation in colder climates
Forest soils, serving as an important sink for atmospheric methane (CH4), modulate the global CH4 budget. However, the direction and magnitude of the forest soil CH4 sink under warming remain uncertain, partly because the temperature response of microbial CH4 oxidation varies substantially across geographical scales. Here, we reveal the spatial variation in the response of forest soil microbial CH4 oxidation to warming, along with the driving factors, across 84 sites spanning a broad latitudinal gradient in eastern China. Our results show that the temperature sensitivity of soil microbial CH4 oxidation significantly declines with increasing site mean annual temperature, with a range of 0.03 to 0.77 μg CH4 g–1 soil d–1 °C–1. Moreover, soil resources and type II methanotrophs play crucial roles in shaping the temperature sensitivity of soil microbial CH4 oxidation. Our findings highlight the importance of incorporating climate, soil resources, and methanotroph groups into biogeochemical models to more realistically predict forest soil CH4 sink under warming.
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