Soil salinization is spread in the dryland of NW China due to the dry or extreme dry climate. Increased salinization damages the health and function of soil systems and influences the microbial community structure and function. Some studies have been conducted to reveal the microbial community structure and isolate the microorganisms of saline soil or salt-lake sediments in this region. However, the functions of microorganisms and their response to salinization, i.e., their adaptation strategy to a wide salinization range in arid environments, are less understood. Here, we applied metagenomics technology to investigate the microbial community structure, function, and their relationship with salinization, and discussed the adaptative strategy of microorganisms to different saline environments. A total of 42 samples were sequenced on the Illumina PE500 platform. The archaea and bacteria constituted the dominant kingdoms; Actinobacteria, Proteobacteria, Bacteroidetes, and Firmicutes were the dominant bacterial phyla; and Euryarchaeota were the dominant archaeal phylum. The microbial communities showed significant structure divergence according to the salt concentration (saline (mean EC 22 mS/cm) and hypersaline (mean EC 70 mS/cm)), wherein the communities were dominated by bacteria in saline soils and archaea in hypersaline soils. Most of the dominant bacterial representation decreased with salinity, while the archaea increased with salinity. KEGG functional annotation showed that at level 2, the cell motility, environmental adaptation, signal transduction, signaling molecules and interaction, glycan biosynthesis and metabolism, and metabolism of other amino acids were reduced from saline to hypersaline, whereas the metabolism of cofactors and vitamins, folding sorting and degradation, replication and repair, transcription and translation, amino acid biosynthesis, glycolysis/gluconeogenesis, and carbon fixation increased with salinity. The increased salt content decreased the carbohydrate activities of microorganisms. The osmolyte regulation substance synthesis and absorption-related genes were more abundant in saline soils than in hypersaline soils, whereas the Na⁺/H⁺ antiporter genes (mnhB-E) and H⁺/Na⁺-transporting ATPase genes (atpA-F, I, K) were significantly higher in hypersaline soils. This indicated that in saline soils, microorganisms primarily synthesize and/or uptake compatible solutes to cope with osmotic stress, whereas in the hypersaline habitat, the high-salt-in strategy was predicated to be adopted by the halophilic/extremely halophilic microorganisms, coupled with a high abundance of replication and repair, cofactors and vitamin metabolism, nucleotide metabolism, and carbon fixation to provide energy and ensure cell regeneration. In conclusion, increases in salinity influence the microbial communities’ structure and function, as well as the adaptation of microorganisms.

Introduction: Salinization damages soil system health and influences microbial communities structure and function. The response of microbial functions involved in the nutrient cycle to soil salinization is a valuable scientific question. However, our knowledge of the microbial metabolism functions in salinized soil and their response to salinity in arid desert environments is inadequate.Methods: Here, we applied metagenomics technology to investigate the response of microbial carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling and the key genes to salinity, and discuss the effects of edaphic variables on microbial functions.Results: We found that carbon fixation dominated the carbon cycle. Nitrogen fixation, denitrification, assimilatory nitrate reduction (ANRA), and nitrogen degradation were commonly identified as the most abundant processes in the nitrogen cycle. Organic phosphorus dissolution and phosphorus absorption/transport were the most enriched P metabolic functions, while sulfur metabolism was dominated by assimilatory sulfate reduction (ASR), organic sulfur transformation, and linkages between inorganic and organic sulfur transformation. Increasing salinity inhibited carbon degradation, nitrogen fixation, nitrogen degradation, anammox, ANRA, phosphorus absorption and transport, and the majority of processes in sulfur metabolism. However, some of the metabolic pathway and key genes showed a positive response to salinization, such as carbon fixation (facA, pccA, korAB), denitrification (narG, nirK, norBC, nosZ), ANRA (nasA, nirA), and organic phosphorus dissolution processes (pstABCS, phnCD, ugpAB). High salinity reduced the network complexity in the soil communities. Even so, the saline microbial community presented highly cooperative interactions. The soil water content had significantly correlations with C metabolic genes. The SOC, N, and P contents were significantly correlated with C, N, P, and S network complexity and functional genes. AP, NH4+, and NO3− directly promote carbon fixation, denitrification, nitrogen degradation, organic P solubilization and mineralization, P uptake and transport, ASR, and organic sulfur transformation processes.Conclusion: Soil salinity in arid region inhibited multiple metabolic functions, but prompted the function of carbon fixation, denitrification, ANRA, and organic phosphorus dissolution. Soil salinity was the most important factor driving microbial functions, and nutrient availability also played important roles in regulating nutrient cycling.

The response of microbiomes to salinity has been clarified in different geographic scales or ecosystems. However, how soil microbial community structure and interaction respond to salinity across wide salinity range and climatic region is still unclearly resolved. To address this issue, we examined the microbial community’s composition in saline soils from two climatic regions (coastal wetland and arid desert). Our research confirms that soil salinity had a negative effect on soil nutrient content. Salinity decreased the relative abundance of bacteria, but increased archaea abundance, leading to the shifts from bacteria dominant community to archaea dominant community. Low-water medium-salinity soil (LWMS) had the most complex archaeal community network, whereas for bacteria, the most complex bacterial community network was observed in low-water high-salinity soils (LWHS). Key microbial taxa differed in three salinity gradients. Salinity, soil water content, pH, total nitrogen (TN), and soil organic carbon (SOC) were the main driving factors for the composition of archaeal and bacterial community. Salinity directly affected archaeal community, but indirectly influenced bacteria community through SOC; pH affected archaeal community indirectly through TN, but directly affected bacterial community. Our study suggests that soil salinity dramatically influences diversity, composition, and interactions within the microbial community.

The change in land use leads to territorial spatial conflict. Territorial spatial conflicts mainly show that the boundaries of agricultural space, urban space, and ecological space overlap each other and interfere with each other’s functions, which will have a negative impact on regional high-quality development. The Aksu River, the most principal source of the Tarim River, the largest instream river in China, is a key area for maintaining ecological security in Northwestern China. It is highly significant to identify the spatial conflict characteristics of land use in this region to promote the sustainable use of regional land resources, optimization of spatial patterns, and the balance between economic construction and ecological environmental protection in mountainous areas. This paper takes the Aksu River Basin as the research area. Using Arcgis 10.8 software, Yaahp software, and SPSSAU software, it builds a land use spatial conflict measurement model based on a quantitative analysis of land use changes from 1990 to 2020 and explores the spatial and temporal evolution characteristics of land use conflicts in the Aksu River Basin. The results show that: (1) From 1990 to 2020, the spatial conflict pattern of the study area was dominated by ecological spatial conflicts. The spatial conflict area shows dynamic changes, but the overall trend is decreasing. (2) The spatial conflict pattern of territorial space in the Aksu River Basin has basically formed, and the three types of spatial conflicts are closely related to the level of local economic development. (3) Ecological spatial conflicts are mainly distributed in high-altitude mountains, river valleys, and oasis-to-desert transition areas. Urban spatial conflicts are mainly distributed in the middle and lower reaches of the Aksu River plain oasis. Agricultural spatial conflicts are scattered but large in scale, with small differences in the proportion of conflict distribution among the counties.

The ecological footprint and ecosystem service functions in the northwest arid region of China have their unique characteristics and are limited by natural resources. The coordination level between the pressure of human activities on the ecosystem and the ecosystem service capacity can be objectively reflected on by exploring the coupling coordination relationship between these two aspects. This work used the ecological footprint and Integrated Valuation of Ecosystem Services and Trade-offs models to quantitatively analyze the spatial and temporal variations of the ecological footprint and ecosystem service functions in the Aksu region in Xinjiang. A coupling coordination degree model and spatial autocorrelation analysis were used to assess the coupling coordination level and spatial agglomeration characteristics of the regional ecological footprint and ecosystem service functions. The results showed that the ecological footprint of the Aksu region has been high in the northeast and low in the southwest, with noticeable spatial heterogeneity, from 2005 to 2018. Carbon (66.17%) and cropland (26.64%) are the main contributing factors to the regional ecological footprint. The biocapacity is dominated by cropland, built-up land, and forest land. The ecological footprint and biocapacity showed an increasing trend, ranging from an ecological surplus to an ecological deficit, with a continued ecological deficit. The level of ecosystem service functions in the Aksu region was low, with significant spatial variability. The high values were concentrated in the northern part of the region and the Tarim and Hotan River Basins. The coupling coordination level of the ecological footprint and ecosystem service functions in the Aksu area was high in the north and low in the south. The aforementioned coupling coordination level was dominated by the spatial pattern of the ecosystem service functions and had noticeable spatial agglomeration characteristics. The coupling coordination degree of the ecological footprint and water supply function showed an upward trend. By contrast, the coupling coordination degree of the ecological footprint with soil conservation and biodiversity maintenance functions showed a downward trend.