Grassland ecosystems, an important component of the terrestrial environment, play an essential role in the global carbon cycle and balance. We considered four different grazing intensities on a Stipa breviflora desert steppe: heavy grazing (HG), moderate grazing (MG), light grazing (LG), and an area fenced to exclude livestock grazing as the Control (CK). The analyses of the aboveground biomass, litter, belowground biomass, soil organic carbon and soil light fraction organic carbon were utilised to study the organic carbon stock characteristics in the S. breviflora desert steppe under different grazing intensities. This is important to reveal the mechanisms of grazing impact on carbon processes in the desert steppe, and can provide a theoretical basis for conservation and utilisation of grassland resources. Results showed that the carbon stock was 11.98–44.51 g m–2 in aboveground biomass, 10.43–36.12 g m–2 in plant litters, and 502.30–804.31 g m–2 in belowground biomass (0–40 cm). It was significantly higher in CK than in MG and HG. The carbon stock at 0–40-cm soil depth was 7817.43–9694.16 g m–2, and it was significantly higher in LG than in CK and HG. The total carbon stock in the vegetation-soil system was 8342.14–10494.80 g m–2 under different grazing intensities, with the largest value in LG, followed by MG, CK, and HG. About 90.54–93.71% of the total carbon in grassland ecosystem was reserved in soil. The LG and MG intensities were beneficial to the accumulation of soil organic carbon stock. The soil light fraction organic carbon stock was 484.20–654.62 g m–2 and was the highest under LG intensity. The LG and MG intensities were beneficial for soil nutrient accumulation in the desert steppe.

Grazing has been shown to impact the soil environment and microbial necromass carbon (MNC), which in turn regulates soil organic carbon (SOC). However, the carbon sequestration potential of fungi and bacteria under different stocking rates remains unclear, limiting our understanding of soil carbon sequestration in grazing management. In 2004, we established grazing experiments in the desert steppe of northern China with four stocking rates. Our findings indicate that MNC decreased under moderate and heavy grazing, while light grazing did not significantly differ from no grazing. Notably, the reduction in fungal necromass carbon, rather than bacterial necromass carbon, was primarily responsible for the decreased contribution of MNC to SOC. This difference is attributed to the varying effects of sheep grazing on fungal and bacterial community characteristics, including richness, diversity, and composition. Thus, to accurately predict carbon dynamics in grassland ecosystems, it is essential to consider that the ecological impacts and carbon sequestration potential of microbial communities may vary with different grazing management practices.

Moisture plays a pivotal role in the establishment of vegetation in sandy areas, underscoring the need to comprehend the water utilization strategies employed by established trees for the judicious use of water resources. Despite this significance, there exists a research gap concerning the water uptake patterns and consumption disparities between the dominant trees, namely the dry willow (Salix matsudana) and small-leafed poplar (Populus simonii), in the Mu Us sandy region. Consequently, our study sought to investigate the water utilization patterns and transpiration water consumption of these two plants. This was achieved through the analysis of hydrogen and oxygen isotope compositions in xylem water, soil water, and groundwater, coupled with the assessment of stem flow rates of tree trunks. The findings reveal that both Salix matsudana and Populus simonii exhibited variations in soil water content with soil depth, characterized by an initial increase followed by a subsequent decrease. During the months of July, August, and September, both species demonstrated the ability to absorb water from multiple sources concurrently. Specifically, Salix matsudana and Populus simonii predominantly utilized middle and shallow soil water sources in July and September, respectively. However, in August, both species primarily relied on shallow soil water for absorption. Over the period from July to September, the sap flow rate of Salix matsudana surpassed that of Populus simonii by 1888.2 mL·h⁻¹ to 2499.04 mL·h⁻¹, representing a 1.5 to 2.2 times increase. This underscores the necessity for Salix matsudana to draw water from middle and deep soil layers to compensate for shallow water deficits. In summary, schemes for the establishment of vegetation in sandy areas should consider the dynamic nature of water uptake and evapotranspiration, emphasizing the importance of regulating these processes for efficient water conservation and utilization.

Soil texture exerts fundamental control over nutrient retention in arid ecosystems; however, its mechanistic coupling with nutrient stoichiometry in wind-eroded desert steppes remains poorly resolved. We investigated soil particle-size distribution and nutrient characteristics across contrasting vegetation types in a desert steppe on the northern slope of the Yinshan Mountains. The interactions between soil texture and nutrient distribution were quantified through field sampling and laboratory analyses. The Caragana grassland was dominated by fine-textured soils, with a silt-to-sand ratio of 21.58% and a fractal dimension ranging from 2.1 to 3.95, indicating a complex soil structure with strong nutrient-retention capacity. In contrast, the Leymus grassland and desert sites were characterized by higher sand content, with a median particle size of 1.67 mm and sorting coefficients ranging from 0.06 to 4.2, reflecting a simpler structure and comparatively lower nutrient levels. Overall, soils in the region were nutrient-deficient, with widespread phosphorus and potassium limitations, whereas nitrogen was relatively more abundant. Total nitrogen (<0.75 mg kg⁻¹), total phosphorus (0.2–0.4 mg kg⁻¹), total potassium and available nutrients were predominantly classified as ‘deficient’ to ‘extremely deficient’, exhibiting a clear surface accumulation pattern. The Poaceae meadow surface layer showed the highest total nitrogen and phosphorus contents. The sorting coefficient and fractal dimension were identified as key particle-size parameters regulating soil nutrient stoichiometric ratios. The silt-to-sand ratio exerted negative path effects (−0.11 to −0.18) on SOC/TN and AK/AN, whereas fractal dimension showed positive path effects (0.17–0.23) on AK/AN. These findings provide a scientific basis for ecological restoration and soil management in the region.

As the risk of drought increases due to climate change, understanding ecological drought has become increasingly important for ensuring water resource security and carbon balance. However, most current ecological drought assessments rely on meteorological or hydrological indicators, which may not accurately reflect changes in the eco-physiological status of ecosystems. Therefore, this study establishes an ecological drought assessment framework using solar-induced chlorophyll fluorescence (SIF) as an indicator to examine its interpretable responses to climate–hydrology–environmental variables. The framework was tested across China’s nine major river basins and different ecosystems. Results show that SIF increased in 80.0% of China’s areas, with 60.9% showing significant increases (p < 0.05). Forest ecosystems experienced the lowest frequency of ecological drought but showed increasing duration and intensity, while grassland ecosystems had the highest frequency but decreasing duration and intensity. LightGBM machine learning analysis revealed that surface soil moisture (SMs), temperature (Tm), root-zone soil moisture (SMrz), and CO₂ were the main factors influencing ecological drought, with SMs and Tm contributing to over 66.1% of ecological drought. The SMs-Tm interaction alleviated ecological drought under low-temperature and high-humidity conditions but initially intensified then alleviated ecological drought under high-temperature and high-humidity conditions. The SMs-CO₂ interaction promoted ecological drought at high or low CO₂ concentrations but alleviated it at moderate concentrations.