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In order to improve the water resources utilization efficiency of the water service area of Middle Route Project of South-to-North Water Diversion, a total of 20 regional units along the project including Beijing and Tianjin as well as 18 provincial cities in Henan and Hebei were taken as the research area. Based on panel data from 2015 to 2021, the Super-SBM model, GML model, and sys-GMM estimation method were used to measure the water resources utilization efficiency of the engineering water receiving area, and the influencing factors were identified. The results indicate that the overall static utilization efficiency of water resources in the entire region is relatively low, but it shows a fluctuating upward trend, with significant regional differences, showing a pattern of Beijing-Tianjin plate>Henan plate>Hebei plate. The spatial distribution of the static utilization efficiency presents a "core-periphery" structure with the two metropolitan areas of Beijing-TianjinHebei and Zhengzhou as the core, which is gradually decreasing outward. The dynamic utilization efficiency of water resources shows a fluctuating upward trend as a whole, which is mainly due to technological progress, but the role of technological efficiency is limited. The factors of economic development level, water resources endowment, science and technology levels, urbanization process and population density are significantly positively correlated with the water resources utilization efficiency, but the factors of water pollution degree, industrial structure and environmental regulation are significantly negatively correlated with the water resources utilization efficiency. [ABSTRACT FROM AUTHOR]

The contamination of soil with the heavy metal cadmium (Cd) is increasingly prominent and severely threatens food security in China. Owing to its low cost, suitable efficacy, and ability to address the shortcomings of plant remediation by enhancing the ability of plants to take up Cd, plant–microbe combination remediation technology has become a research hotspot in heavy metal pollution remediation. A pot experiment was performed to examine the effects of inoculation with the plant-growth-promoting bacterium Brevibacillus sp. SR-9 on the biomass, Cd accumulation, and soil nutrients of hybrid Pennisetum. The purpose of this study was to determine how Brevibacillus sp. SR-9 alleviates stress caused by heavy metal contamination. High-throughput sequencing and metabolomics were used to determine the effects of inoculation on the soil bacterial community composition and microbial metabolic functions associated with hybrid Pennisetum. The results suggest that mutation of Brevibacillus sp. SR-9 effectively alleviates Cd pollution stress, leading to increased biomass and accumulation of Cd in hybrid Pennisetum. The aboveground biomass and the root weight increased by 12.08% and 27.03%, respectively. Additionally, the accumulation of Cd in the aboveground sections and roots increased by 21.16% and 15.50%, respectively. Measurements of the physicochemical properties of the soil revealed that the strain Brevibacillus sp. SR-9 slightly increased the levels of available phosphorus, total nitrogen, total phosphorus, and available potassium. High-throughput DNA sequencing revealed that Brevibacillus sp. SR-9 implantation modified the composition of the soil bacterial community by increasing the average number of Actinobacteria and Bacillus. The total nitrogen content of the soil was positively correlated with the Actinobacteria abundance, total phosphorus level, and available phosphorus level. Metabolomic analysis revealed that inoculation affected the abundance of soil metabolites, and 59 differentially abundant metabolites were identified (p < 0.05). Among these, 14 metabolites presented increased abundance, whereas 45 metabolites presented decreased abundance. Fourteen metabolic pathways were enriched in these metabolites: the folate resistance pathway, the ABC transporter pathway, D-glutamine and D-glutamic acid metabolism, purine metabolism, and pyrimidine metabolism. The abundance of the metabolites was positively correlated with the levels of available phosphorus, total potassium, total phosphorus, and total nitrogen. According to correlation analyses, the development of hybrid Pennisetum and the accumulation of Cd are strongly associated with differentially abundant metabolites, which also impact the abundance of certain bacterial populations. This work revealed that by altering the makeup of microbial communities and their metabolic processes, bacteria that promote plant development can mitigate the stress caused by Cd. These findings reveal the microbiological mechanisms through which these bacteria increase the ability of hybrid Pennisetum to take up the Cd present in contaminated soils. [ABSTRACT FROM AUTHOR]

Shrub encroachment became widespread in grass-dominated ecosystem regions. However, there is still limited attention on the changes in plant-soil system C:N:P stoichiometry and soil microbial metabolic limitation status caused by anthropogenic encroachment of shrubs in the desert grassland of northwest China, as well as their driving mechanisms. In this study, we quantified the C:N:P stoichiometry of plant-litter-soil, soil physicochemical properties, microbial biomass, extracellular enzyme activities, and microbial metabolic limitation status during the anthropogenic transition from grassland to shrubland. Here, our results showed that anthropogenic shrub encroachment reduced plant C, soil water, and soil nutrient contents while increasing N and P contents in both plants and litter. The correlation also suggested that litter nutrient content relied on plant nutrients, while plants depleted soil nutrients. Secondly, with the gradient of shrub encroachment, the stoichiometry (except for soil C:N ratio) of plant-litter-soil showed a decreasing trend and a positive correlation. Furthermore, our study indicated that shrub encroachment reduced soil microbial biomass and extracellular enzyme activities, altering microbial stoichiometry and patterns of enzyme allocation. Redundancy analysis revealed that microbial biomass, extracellular enzyme activities, and stoichiometry were mainly driven by soil water content, nutrient content, and nutrient stoichiometry. The vector-threshold element ratio model revealed that along the transition from desert grassland to shrubland, soil microbial nutrient limitation shifted from P to N, while energy (C) limitation intensified. The soil microbial metabolic limitation was driven jointly by plants and litter through modifications of soil properties and microbial biomass. Additionally, soil properties played a crucial role among these factors. In summary, over the past 40 years, shrub anthropogenic encroachment has formed a desert grassland-shrub mosaic landscape, depleted soil water and nutrient contents, and altered ecological stoichiometry and microbial metabolic limitation patterns in northwest China. This study provides new insights into the C, N, and P cycling in plant-soil systems following shrub encroachment caused by global climate change and anthropogenic disturbances. [Display omitted] • The C:N:P stoichiometry (except for soil C:N) of plant-litter-soil was coupled. • Soil microbial biomass and extracellular enzymes were regulated by soil water and nutrients. • Soil microbial nutrient limitation from P to N with shrub encroachment • Soil microbial energy (C) limitation increased with shrub encroachment. • Soil microbial metabolic limitation was primarily driven by soil properties. [ABSTRACT FROM AUTHOR]

Clarifying how soil microbial communities respond to shrub introduction after overgrazing in desert steppe and their potential functions is crucial for understanding the biogeochemical processes involved in vegetation transformation and sustainability of desert grasslands. However, the dynamics of microbial communities remain poorly understood. We selected enclosed grasslands (20a), overgrazed grasslands, and shrublands (6a, 15a, and 25a) to explore how shrubs introduced influence soil microbial structure and functional groups over the long term after desert grassland degradation. The results showed that overgrazing and shrub introduction (Caragana korshinskii) had more significant impacts on microbial β diversity than on α diversity. Fungal communities were more sensitive to grassland degradation. In contrast, introducing shrubs affected both fungal and bacterial communities, and an increase in shrub age drove the synergistic effects of fungal species. Soil nitrate and microbial biomass nitrogen were the key factors affecting bacterial and fungal communities. Compared with enclosed grasslands, overgrazing and introducing shrubs significantly increased soil nitrate reduction, ectomycorrhizals, and endophytes. The introduction of shrubs after overgrazing in desert steppe further enhanced the decomposition of carbon compounds and reduced processes such as denitrification. During shrub introduction, total phosphorus, nitrate–nitrogen, and N-acetylglucosaminidase were key factors affecting carbon, nitrogen, and fungal functional groups. Variations in microbial diversity and functional groups, through their influence on extracellular enzymes activity and the availability of microbial biomass nutrients, ultimately explained 85%, 42%, and 34% the observed variations in soil carbon, nitrogen, and phosphorus content, respectively. This study aimed to investigate the long-term effects of anthropogenic shrub expansion on the structure and function of soil microbial communities in degraded desert steppes, provide a scientific basis for steppe restoration and management, and further understand their significance for ecosystem sustainability. • Shrub introduction has significantly altered fungal and bacterial communities. • Shrub age drive fungal community structure towards more synergistic directions. • The function of fungi is shifting from pathotroph to symbiotroph and saprotroph. • Shrubs enhances the degradation carbon compounds and improves nitrate reduction. • Soil nitrogen and extracellular enzymes primarily shape microbial community. [ABSTRACT FROM AUTHOR]

Background: Metal(loid)s can promote the spread and enrichment of antibiotic resistance genes (ARGs) in the environment through a co-selection effect. However, it remains unclear whether exposure of microorganisms to varying concentrations of selenium (Se), an essential but potentially deleterious metal(loid) to living organisms, can influence the migration and distribution of ARGs in forest soils. Results: Precisely 235 ARGs conferring resistance to seven classes of antibiotics were detected along a Se gradient (0.06–20.65 mg kg−1) across 24 forest soils. (flor)/(chlor)/(am)phenicol resistance genes were the most abundant in all samples. The total abundance of ARGs first increased and then decreased with an elevated available Se content threshold of 0.034 mg kg−1 (P = 2E−05). A structural equation model revealed that the dominant mechanism through which Se indirectly influences the vertical migration of ARGs is by regulating the abundance of the bacterial community. In addition, the methylation of Se (mediated by tehB) and the repairing of DNA damages (mediated by ruvB and recG) were the dominant mechanisms involved in Se resistance in the forest soils. The co-occurrence network analysis revealed a significant correlated cluster between Se-resistance genes, MGEs and ARGs, suggesting the co-transfer potential. Lelliottia amnigena YTB01 isolated from the soil was able to tolerate 50 μg mL−1 ampicillin and 1000 mg kg−1 sodium selenite, and harbored both Se resistant genes and ARGs in the genome. Conclusions: Our study demonstrated that the spread and enrichment of ARGs are enhanced under moderate Se pressure but inhibited under severe Se pressure in the forest soil (threshold at 0.034 mg kg−1 available Se content). The data generated in this pilot study points to the potential health risk associated with Se contamination and its associated influence on ARGs distribution in soil. [ABSTRACT FROM AUTHOR]

In this study, spatio-temporal characteristics of particulate matter (PMx; x = 2.5 and 10) mass concentrations and aerosol optical properties were analyzed over the water source area of the South–North Water Diversion Central Line. For this purpose, PM2.5 and PM10 mass concentrations were collected at the Taocha(TC)station from October 2018 to September 2019, and aerosol optical depth (AOD) was obtained from the Cloud-Aerosol LiDAR and Infrared Pathfinder Satellite Observation (CALIPSO) satellite from 2007 to 2019. The monthly, seasonal, and daily statistical analyses and related comparisons were conducted in the present study. The results showed that the PM10 concentrations meet China's ambient air secondary quality standard (100 μg/m3 annual mean), whereas PM2.5 did not meet China's ambient air secondary quality standard (35 μg/m3 annual mean) at the TC station, no obvious seasonal and diurnal variations are observed, and these particulates are caused by local emissions and outside sources. A significant positive correlation of PM2.5 and PM10 was observed with relative humidity and temperature, whereas no relationship was found with wind direction. The results also showed low (~0.1) AOD in spring, autumn, and winter, whereas slightly higher AOD (~0.3) was observed in summer. This may be caused by straw burning from long-distance transportation. This study may provide new data support for comprehensive ecological measures such as strengthening the ecological environment and water quality protection in the Middle Route Project of the South–North Water Diversion. [ABSTRACT FROM AUTHOR]