Introduction: Soil organic carbon (SOC) dynamics and microbial drivers in arid regions are critical for ecosystem restoration and carbon sequestration. This study investigated how converting cropland to artificial grasslands influences SOC fractions and the community of carbon-fixing microorganisms in the arid region of Urumqi, Xinjiang, China. Methods: We established two types of artificial grasslands—grassy (GG) and leguminous (LG)—and compared them against adjacent cropland (CK). We analyzed SOC fractions, including particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), and measured cumulative carbon mineralization. The abundance of the cbbL gene was quantified by quantitative PCR. The composition of the cbbL-harboring microbial community was characterized by sequencing the cbbL gene amplicons. Results: The MAOC content was significantly higher in GG than in CK and LG. Although the proportion of POC was higher in CK, its absolute content was lowest in LG. Cumulative carbon mineralization was significantly lower in CK than in GG and LG. The cbbL gene abundance was highest in LG. A total of 47,026 cbbL gene amplicon sequence variants were identified, predominantly from Proteobacteria and Actinobacteria , with facultative autotrophs as the dominant functional group. Compared to CK, both grassland types increased the relative abundance of Actinobacteria but decreased that of Planctomycetes . At the genus level, LG significantly enriched SinoRhizobium and MesoRhizobium , whereas GG promoted Microvirga and Bradyrhizobium . Discussion: Mantel tests identified soil pH, the proportions of soil aggregates (>2 mm, 2–0.25 mm, and <0.053 mm), electrical conductivity, and MAOC content as the key environmental factors shaping the carbon-fixing microbial community. These results demonstrate that the establishment of artificial grasslands, particularly leguminous types, enhances the potential for soil carbon sequestration by modulating key soil properties and enriching specific carbon-fixing microbial taxa. This study provides a scientific basis for using artificial grasslands to enhance ecological restoration and soil carbon sequestration in arid regions.

In modern livestock production, a reliable supply of high-quality forage is essential for sustaining animal productivity and product quality. Although nitrogen (N) fertilization can promote forage growth, excessive N inputs often result in low agronomic nitrogen use efficiency (NAUE) and increased environmental risks. Biochar, owing to its porous structure, high specific surface area, and physicochemical stability, can improve soil physical properties, enhance water and nutrient retention, and regulate soil N availability. However, the mechanisms by which biochar combined with reduced N rate fertilization affects NAUE in artificial grasslands remain insufficiently quantified. A two-year field experiment was conducted at the Grassland Science Experimental Station of Xinjiang Agricultural University on the northern slope of the Tianshan Mountains, Xinjiang, China. Eight treatments were established using a factorial design with two biochar rates (0 and 20 t·ha⁻¹; B0 and B20) and four N application rates (0, 75, 150, and 225 kg·ha⁻¹; N0, N75, N150, and N225). Results showed that biochar application significantly decreased soil bulk density and increased soil water content and electrical conductivity. It also elevated soil total carbon, total nitrogen, total phosphorus, NH₄⁺–N, and NO₃⁻–N concentrations, with B20N150 exhibiting the highest overall nutrient status. Plant community diversity indices did not differ significantly among treatments (p > 0.05), though B20 slightly enhanced Shannon–Wiener and Simpson indices under N0 and N75. Moderate N application significantly increased hay yield, whereas the highest N rate (225 kg·ha⁻¹) did not further improve yield and reduced NAUE. Biochar combined with N75 or N150 improved NAUE, and B20N150 achieved the best balance of high hay yield and high NAUE. Structural equation modeling revealed that soil water content (path coefficient = 0.45), NH₄⁺–N (0.27), and plant community diversity (0.20) were key positive drivers of NAUE, with biochar exerting indirect effects primarily via improving soil water and available N. Collectively, applying 20 t·ha⁻¹ biochar with 150 kg·ha⁻¹ N (B20N150) is recommended as an optimal strategy for N rate reduction and NAUE enhancement in artificial grasslands of arid and semiarid regions.

To tackle the low nitrogen-use efficiency, water scarcity, and insufficient forage supply in improved grasslands in arid Northwest China, a two-factor field trial involving three biochar dosages (0, 10, 20 t ha⁻¹) and two nitrogen (N) application rates (0, 225 kg ha⁻¹) was conducted on mountain grassland in Xinjiang, with Onobrychis viciifolia and Bromus inermis as test forages. Soil physicochemical traits, soil–forage and water–nitrogen dynamics, forage productivity, and economic returns were determined, and partial least squares path modeling (PLS-PM, GoF = 0.373) was conducted to quantify the regulatory pathways. Co-treatments with biochar and N markedly lowered soil bulk density and elevated porosity, soil organic carbon, and the available N pool; application of biochar deferred the peak of soil available N and prolonged fertilizer efficacy by more than seven days. Forage total nitrogen- and water-use efficiency peaked at the first cutting, with the B1N1 treatment (10 t ha⁻¹ biochar + 225 kg ha⁻¹ N) boosting water-use efficiency by 45.2%. O. viciifolia exhibited optimal performance under B1N15, while B2N15 (20 t ha⁻¹ biochar + 225 kg ha⁻¹ N) was more favorable for B. inermis. The B1N15 regime achieved the highest net profit of CNY 12,747.99 ha⁻¹, but high biochar input cut economic gains by 14.1%. The PLS-PM model uncovered a dual regulatory mechanism: combined amendments directly optimized soil microhabitats, and soil water–nitrogen conditions served as a central mediator to facilitate biomass accumulation and economic gains through cascading soil–vegetation transmission, without direct impacts on vegetation productivity or economic outputs. This research provides a scientific reference for the use of fertilization in the sustainable management of arid improved grasslands.

As integral components of ecosystems, rodents exhibit high sensitivity to environmental fluctuations. As a typical semi-subterranean rodent, the burrowing and foraging behaviors of the mole vole (Ellobius tancrei) profoundly impact local microhabitat structure and vegetation succession. Given its extensive distribution range, investigating the geographical distribution of the mole vole under climate change is critical for understanding its population dynamics and spatial patterns. To explore the impacts of climate change on the potential distribution of this species, we utilized an ensemble model based on 395 occurrence records and 38 environmental variables. We predicted its potential geographical distribution under current (1970–2000) and three future climate scenarios (SSP126, SSP245, and SSP585) across three future periods (2041–2060, 2061–2080, and 2081–2100) and further analyzed the variation trends and centroid migration directions of its global potential distribution. The results revealed the following: (1) Elevation (Dem) and temperature annual range (Bio7) were the dominant environmental factors driving the potential distribution of the mole vole, followed by precipitation of the warmest quarter (Bio18), mean diurnal range (Bio2), annual mean temperature (Bio1), base saturation (BSAT), precipitation seasonality (Bio15), calcium carbonate content (TCARBON_EQ), and available water capacity (AWC). (2) Under current climate conditions, the highly suitable habitats were mainly concentrated in Eurasia, particularly in Turkey, Kyrgyzstan, China, Mongolia, and Russia. (3) Under future climate scenarios, suitable habitats showed simultaneous expansion and contraction, with expansion consistently exceeding contraction across all scenarios and periods, especially under SSP585 in the late 21st century. (4) Relative to the current period, the suitable-habitat centroid shifted northeastward under SSP126, but northwestward under SSP245 and SSP585. This study reveals the dynamic spatial shifts of the mole vole driven by climate change, not only providing crucial scientific support for early spatial warning and precise prevention of agricultural and pastoral rodent damage, but also laying a theoretical foundation for understanding the ecological adaptation mechanisms of subterranean rodents and mitigating potential cross-regional dispersal risks.