Optimizing the spatial pattern of carbon sequestration service is essential for advancing regional low-carbon development, accelerating the achievement of the "dual carbon" goals, and promoting the high-quality development of ecological environment. The carbon sequestration capacity within the mountain-desert-oasis system (MDOS), a unique landscape pattern, exhibits significant gradient characteristics, and its carbon sink potential can be substantially improved through multi-scale spatial optimization. This study employed the Integrated Valuation of Ecosystem Services and Tradeoff (InVEST) model to estimate carbon storage and sequestration (CSS) in the Gansu section of Heihe River Basin, China, a representative MDOS, based on land use/land cover (LULC) data from 1990 to 2020. The Patch-level Land Use Simulation (PLUS) model was coupled to simulate LULC and estimate carrying CSS under natural development (ND), ecological protection (EP), water constraint (WC), and economic development (ED) scenarios for 2035. Furthermore, the study constructed and optimized the CSS pattern on the basis of economic and ecological benefits, exploring the guiding significance of different scenarios for pattern optimization. The results showed that CSS spatial distribution is closely correlated with LULC pattern, and CSS is expected to improve in the future. CSS showed an overall increase across subsystems during 1990-2020, but varied across LULC types. CSS of construction land in all subsystems exhibited an increasing trend, while CSS of unused land showed a decreasing trend, with specific changes of 1.68×10³ and 3.43×10⁵ t, respectively. Regional CSS dynamics were mainly driven by conversions among unused land, cultivated land, and grassland. The CSS pattern of MDOS was divided into carbon sink functional region (CSFR), low carbon conservation region (LCCR), low carbon economic region (LCER), and economic development region (EDR). Water resources coordination served as the basis of pattern optimization, while the four dimensions—ecological carbon sink, low-carbon maintenance, agricultural carbon reduction and sink enhancement, and urban carbon emission reduction—framed the optimization framework. ND, EP, WC, and ED scenarios provided guidance as the basic reference, optimal benefit, "dual carbon" baseline, and upper development limit, respectively. Additionally, the detailed CSS sub-partitions of MDOS covered most potential scenarios of such ecosystems, demonstrating the applicability of these sub-partitions. These findings provide valuable references for enhancing CSS and hold important significance for low-carbon territorial spatial planning in the MDOS.

The Wuding River Basin, situated in the Loess Plateau of northern China, is an ecologically fragile region facing severe soil erosion and imbalanced ecosystem service (ES) functions. However, the mechanisms driving the spatiotemporal evolution of ES functions, as well as the trade-offs and synergies among these functions, remain poorly understood, constraining effective watershed-scale management. To address this challenge, this study quantified four ES functions, i.e., water yield (WY), carbon storage (CS), habitat quality (HQ), and soil conservation (SC) in the Wuding River Basin from 1990 to 2020 using the Integrated Valuation of Ecosystem Services and Tradeoff (InVEST) model, and proposed an innovative integration of InVEST with a Bayesian Belief Network (BBN) to nonlinearly identify trade-off and synergy relationships among ES functions through probabilistic inference. A trade-off and synergy index (TSI) was developed to assess the spatial interaction intensity among ES functions, while sensitivity and scenario analyses were employed to determine key driving factors, followed by spatial optimization to delineate functional zones. Results revealed distinct spatiotemporal variations: WY increased from 98.69 to 120.52 mm; SC rose to an average of 3.05×10⁴ t/hm²; CS remained relatively stable (about 15.50 t/km²); and HQ averaged 0.51 with localized declines. The BBN achieved a high accuracy of 81.9% and effectively identified strong synergies between WY and SC, as well as between CS and HQ, while clear trade-offs were observed between WY and SC versus CS and HQ. Sensitivity analysis indicated precipitation (variance reduction of 9.4%), land use (9.8%), and vegetation cover (9.1%) as key driving factors. Spatial optimization further showed that core supply and ecological regulation zones are concentrated in the central-southern and southeastern basin, while ecological strengthening and optimization core zones dominate the central-northern and southeastern margins, highlighting strong spatial heterogeneity. Overall, this study advances ES research by combining process-based quantification with probabilistic modeling, offering a robust framework for studying nonlinear interactions, driving mechanisms, and optimization strategies, and providing a transferable paradigm for watershed-scale ES management and ecological planning in arid and semi-arid areas.

With ongoing global climate change, drought has become the primary threat constraining food security in China. Traditional assessment frameworks based on administrative boundaries or macro-climatic zoning overlook variation in vulnerability affected by key agronomic practices, such as crop phenology and cropping systems, thereby limiting their accuracy. To address this research gap, this study developed and validated a novel drought risk assessment framework based on agricultural cropping zones (single-, double-, and triple-cropping zones). The framework coupled a Geographical and Temporal Neural Network Weighted Regression (GTNNWR) model for forecasting future crop vegetation dynamics with the Standardized Precipitation Evapotranspiration Index (SPEI) to assess drought risk under historical (2001-2020) and projected future (2021-2100) scenarios. The GTNNWR model achieved R² values ranging from 0.72 to 0.82 and RMSE values between 0.11 and 0.14 for NDVI prediction, significantly outperforming conventional models. Historical drought risk assessment revealed that drought events were most frequent during summer and concentrated in single-cropping and double-cropping zones. Future projections indicate a substantial intensification of drought risk. Under the Shared Socioeconomic Pathway (SSP)126 scenario, drought risk is projected to increase in the triple-cropping zones of the middle and lower reaches of the Yangtze River Plain. Under the SSP245 scenario, the frequency of spring and winter droughts is anticipated to rise markedly. Under the SSP585 scenario, drought intensity is projected to intensify in central-eastern single-cropping zones and southwestern double-cropping zones. This assessment framework based on agricultural cropping zones can precisely identify drought risks and facilitate adaptation in agricultural management, such as optimizing irrigation systems and adjusting crop structures.

Due to the arid and sandy surface of the Taklimakan Desert (TD) in China, the turbulence structure and vertical distribution of ozone exhibit unique and complex characteristics. However, few studies have focused on these issues. To reveal the variation characteristics of summertime atmospheric turbulence and ozone concentration over the TD, we conducted joint detection experiments in July 2016 and July 2021 at Tazhong in the hinterland of the TD using an eddy covariance detection system, a GPS (Global Positioning System) sounding system, and a meteorological gradient tower. Using methods such as statistical analysis, nonlinear fitting, and Fast Fourier Transform, this study analyzed and processed parameters including temperature, relative humidity, wind speed, turbulence parameters, turbulence spectra, and ozone concentration. The high average temperature is accompanied by low relative humidity over the TD, showing a negative correlation between the two. The temperature of the 10.0-cm-deep sand layer lags the near-surface air temperature by nearly 4 h. From 09:30 to 21:00 (Beijing Time), under conditions where the sensible heat flux is positive but stability parameter (z/L, where z is the height and L is the Obukhov length) is negative, the atmosphere is heated by the land surface, with the occurrence of unstable stratification; however, the conditions are the opposite (sensible heat flux is negative and z/L is positive) after 22:00, which are accompanied with the cooling of the surface radiation, occurrence of temperature inversion in the lower atmosphere, and stable stratification. A positive correlation is identified between the diurnal variation of turbulent kinetic energy (TKE) and the atmospheric boundary layer (ABL) height, with significant contributions from both the buoyancy and shear terms during the daytime. Under unstable stratification, the normalized standard deviations of the three-dimensional wind speed, temperature, and humidity conform to the Monin-Obukhov Similarity Theory (MOST). As the stability parameter z/L transitions from strongly unstable to strongly stable, the energy of the dimensionless turbulent velocity spectra gradually decreases and conforms to the -2/3 power law within the inertial subrange. In the hinterland of the TD, the summertime tropospheric ozone concentration remains below approximately 0.70×10^-6 (volume concentration). Above the troposphere, within the range of 16,500.0-30,000.0 m, a significant increasing trend is identified in the ozone concentration with altitude. At an altitude of 30,000.0 m, the maximum ozone concentration can reach up to 7.50×10^-6. The research findings provide both theoretical and data foundations for future in-depth studies of turbulent motion and ozone concentration distribution in the TD, as well as in the similar areas around the world.

Amid global precipitation changes, it remains unclear whether hydrological niche separation (HNS) mechanisms apply to herbaceous plant communities in desert steppes are severely affected by seasonal drought. How these plants access limited water and tolerate drought to coexist also remains unverified. In this study, we employed stable isotope techniques to examine water acquisition and drought adaptation in coexisting species of the desert steppe in northern China under five precipitation treatments, i.e., decreased 50%, decreased 30%, ambient, increased 30%, and increased 50% precipitation. The following results showed that: (1) water sources of coexisting species shifted with changes in precipitation amount and timing, i.e., all coexisting plants exhibited preferential utilization of surface soil moisture. When surface soil moisture was scarce, they shifted to deeper water sources, and when deep water sources remained scarce, they were forced to compete more intensely for surface water sources; (2) community's HNS was affected by precipitation amount but not by timing, i.e., with adequate soil moisture, plant water source ranges expanded, reducing overlap and enhancing HNS, whereas under extreme drought, the range contracted and increased the overlap, although HNS remained stable; and (3) water acquisition strategies of coexisting species differed along hydrological niche axis defined by water stress adaptability (i.e., stable carbon isotope composition and proline content). Convolvulus ammannii Desr. had the strongest drought adaptation, although its strategy showed a weak correlation with water uptake. Stipa breviflora Griseb., with moderate drought resistance, adopted a water-conserving strategy that was suitable for extreme drought. Leymus secalinus (Georgi) Tzvelev, Polygala tenuifolia Willd., and Larix potaninii Batalin showed resource-dependent and flexible water strategies, thriving in wetter soils but struggling under extreme drought. Our findings indicated that herbaceous species in desert steppes adapted their water uptake and drought tolerance strategies according to changes in precipitation amount and timing. As a core regulatory mechanism, HNS (under increasing precipitation variability due to climate change) not only supports species coexistence by reducing interspecific competition, but also promotes efficient soil moisture use. This mechanism enhances community drought resistance and contributes to ecosystem stability. Overall, this study provides key ecological evidence for understanding plant community adaptation in arid and semi-arid areas facing the influence of global climate change.

Over the past six decades, the implementation of soil and water conservation measures has significantly reduced soil erosion and sediment yield on the Loess Plateau, China. However, while the overall reduction is well-documented, the dynamic interplay between soil erosion potential and sediment connectivity, specifically how they spatially covary under land use/cover changes, remains insufficiently understood. To address this gap, this study established a model framework by integrating the revised universal soil loss equation (RUSLE), index of connectivity (IC), and sediment delivery ratio (SDR) to evaluate the spatio-temporal variations in soil erosion and sediment yield in the Hantaichuan Watershed, northern Loess Plateau, China, from 1995 to 2020 and to estimate the effects of land use/cover changes and check dam construction on sediment yield. The results revealed that the soil erosion in the Hantaichuan Watershed decreased by 43.90% from 1995 to 2020 and the sediment yield decreased by 69.28% under the combination of land use/cover changes and check dam construction. The IC and soil erosion (IC-SE) map revealed both the coupling and decoupling covariation relationships between sediment connectivity and soil erosion. By 2020, areas with high connectivity and high erosion (I-E) covered only 18.67% of the watershed, while contributed more than 40.00% to the total erosion. The I-E zones were mainly located in the central part of the watershed where aeolian sands derived from the Hobq Desert are concentrated and were identified as critical areas for soil and water conservation. This study provides support for priority management of watershed conservation measures as well as a valuable reference for future studies.

Climate warming and humidification trends have significantly influenced vegetation growth patterns in Chinese semi-arid areas. Exploring vegetation dynamics is crucial for understanding regional ecosystem structure and improving the efforts of ecosystem restoration. However, the applicability of various vegetation indices (VIs) in these arid areas remains uncertain. Evaluating the applicability of multiple VIs for vegetation monitoring can elucidate the variability of VIs performance at regional scale. Therefore, this study selected the Zuli River Basin (ZLRB), a typical loess hilly watershed in the semi-arid areas of China. Using Landsat data, we calculated the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and kernel NDVI (kNDVI) for the ZLRB from 1990 to 2020. We analyzed the spatiotemporal variations of these VIs using trend analysis and the Mann-Kendall test, and quantified the contributions of climate change (considering time-lag effects) and human activities to VIs changes through wavelet and residual analyses. Results indicated that VIs generally exhibited an upward trend in the ZLRB, with significant improvements observed in 54.91% of the area for NDVI, 31.69% for EVI, and 33.71% for kNDVI. Among them, NDVI outperformed EVI and kNDVI in capturing vegetation changes in the semi-arid area. VIs responded to precipitation with 1-month time lag and no time lag to temperature during growing season. Moreover, precipitation had a stronger positive correlation with VIs than temperature. Climate change was identified as the dominant driver of vegetation dynamics in the ZLRB, accounting for 93.12% of NDVI variation, while human activities contributed only 6.88%. Comparative analysis of VIs suggests that NDVI was more suitable for describing vegetation changes in the typical arid area of the ZLRB. Our findings underscore the importance of selecting appropriate VIs for targeted ecological restoration and sustainable land management.

Soil erosion and shallow landslides in the upper reaches of the Yellow River, China, are increasing due to extreme climate events and human disturbances. The biomechanical properties of vegetation roots play an important role in soil stabilization and fixation, as they resist soil erosion and shallow landslides in this area. However, the biomechanical properties of the roots of dominant herbs and their influencing factors in this area remain poorly understood. Therefore, we selected two dominant herbs in this area, Stipa aliena Keng and Poa crymophila Keng, and carried out a series of uniaxial tensile tests on the roots of the two herbs under different treatments. Meanwhile, the effects of root diameter, plant species, gauge length, root water content, and loading rate on the biomechanical properties of the two herbs' roots were analyzed. The results showed that root diameter was the most significant factor affecting the root biomechanical properties (P<0.010), and root tensile force displayed a positive power law relationship with root diameter, whereas root tensile strength and Young's modulus followed negative power law correlations with root diameter, and fracture strain increased linearly with root diameter. Root tensile force, tensile strength, and fracture strain of S. aliena were significantly greater than those of P. crymophila (P<0.001), which was mainly due to the higher lignin content and lignin:cellulose ratio of S. aliena roots. During uniaxial tensile process, hydrated roots exhibited elastic-plastic-brittle behavior, whereas dried roots exhibited elastic-brittle behavior. Root fracture strain of the two herbs was significantly lower under 100 mm gauge length than under 50 mm gauge length (P<0.001), and the Young's modulus was significantly greater (P<0.050). Tensile strength and fracture strain of hydrated roots of the two herbs were significantly greater than those of dried roots (P<0.050), whereas the Young's modulus was significantly lower (P<0.001). Root tensile force, tensile strength, and fracture strain of S. aliena were significantly greater under 20 mm/min loading rate than under 200 mm/min loading rate (P<0.050), whereas loading rate had no significant effect on the root biomechanical properties of P. crymophila (P>0.050). Fibrous roots of the two herbs were well developed, with relatively high tensile strengths and Young's moduli of 78.498 and 837.901 MPa for S. aliena, and 67.541 and 901.184 MPa for P. crymophila, respectively. The two herbs can stabilize soil and prevent soil erosion and can be used as pioneer species for ecological restoration in the upper reaches of the Yellow River. These results provide a theoretical basis for soil erosion and shallow landslide control in the giant landslide area of the upper reaches of the Yellow River.