This study discusses the impact of two different ecological restoration approaches on the distribution of soil particle size and organic carbon, expecting to provide references for research on the effects of ecological restoration on the soil carbon pool in alpine regions. By replacing the method of time sampling with spatial sampling, grasslands enclosed only in the growing season and woodlands enclosed all year round were respectively selected as the research objects. Through centrifugation, the soil samples were classified by grain size into sand (50–2000 μm), silt (2–50 μm), and clay (<2 μm) to analyze the distribution of organic carbon in soil particles of different sizes. The major findings were as follows. First, sand accounted for the largest proportion of all the soil components in the grasslands and woodlands that had been restored for different years, followed by silt and clay. Second, most of the organic carbon in the grasslands and woodlands was from sand and silt. As the restoration years increased, the proportion of organic carbon in clay grew in fluctuation. In short, both ecological restoration approaches have improved the soil structure and raised the content of soil organic carbon (SOC). Specifically, the restoration scheme of the woodlands exerted a more significant influence on the soil components and the distribution of organic carbon than that of the grasslands.

This study, based on stable hydrogen and oxygen isotope observations of multiple water bodies (precipitation, river water, soil water, and groundwater) in the Ami Dongsou alpine arid watershed on the southern slope of the Qilian Mountains during 2023–2024, reveals significant seasonal fluctuations in water isotope characteristics and water source renewal mechanisms. The results show that precipitation and soil water exhibit notable enrichment during the dry season, primarily due to enhanced evaporation causing light isotopes to evaporate and heavy isotopes to accumulate. River water, influenced by both precipitation recharge and evaporation, shows smaller seasonal fluctuations. Groundwater isotopes remain stable, reflecting a slower water source renewal process with minimal seasonal influence. Through quantitative comparisons of the evaporation line’s slope and intercept, this study finds that precipitation is most significantly affected by evaporation, while groundwater is least influenced, showing more stable isotope characteristics. Climate and topography in high-altitude areas significantly regulate water isotope characteristics, especially during the dry season, where evaporation plays a dominant role in the enrichment of precipitation and river water isotopes. This study innovatively establishes an evidence framework for the linkage of multiple water body isotopes, revealing the “seasonal strong fluctuations + differential water body responses + high-altitude regulation” mechanism of water isotopes in alpine arid regions. It provides new data support for water resource management, particularly in aspects such as water source allocation during the dry season, groundwater protection, and evaporation enrichment effect prediction. Future research could expand the sample size and integrate multi-source data and hydrological models to further improve the accuracy of hydrological process predictions, offering more precise support for watershed water resource management and ecological protection.

Understanding plant water-use strategies in cold-arid alpine regions is essential for assessing the critical zone processes under changing climate conditions. This study investigates the ecohydrological heterogeneity and water-use efficiency (WUE) across multiple vegetation types in the Xiangride-Qaidam River Basin, located in the northeastern Qinghai-Tibet Plateau, which represents a critical zone of interaction between water, soil, and vegetation. Using stable isotope tracing (δ18O, δ2H), soil and leaf water content analysis, and WUE estimation, we explored how nutrient cycling, evaporation-driven fractionation, and vegetation adaptation regulate water-use patterns and biogeochemical processes in this key environment. Results revealed distinct ecosystem responses to hydrological conditions: (1) Soil water content (SWC) declined markedly from alpine meadows (26.78%) to desert shrubs (3.8%), whereas leaf water content (LWC) increased along this gradient, peaking in desert shrubs (49.12%) and declining in alpine steppes (19.06%); (2) Summer precipitation exhibited sub-cloud evaporation signatures, with the local meteoric water line (δ2H = 6.34δ18O + 9.73) deviating significantly from the global meteoric water line; (3) Isotopic homogeneity in river and groundwater indicated shared recharge pathways; (4) WUE exhibited strong ecosystem divergence, with alpine and saline meadows showing the highest WUE (>63 μmol·mol⁻¹), while desert shrubs had the lowest (50.28 μmol·mol⁻¹), reflecting adaptation trade-offs under water-limited conditions. These findings highlight the role of hydrological-biogeochemical coupling in regulating plant water-use strategies and ecosystem stability in cold-arid alpine critical zones. This study addresses how coupled water, nutrient cycling, and vegetation dynamics are shaped by climate-driven hydrological extremes and land-use change, offering insights into critical zone processes in high-altitude, water-limited environments.