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The Water Conservation Functional Zone and Ecological Environmental Supporting Zone (the Capital Two Zones in China), Zhangjiakou (ZJK) City, situated in China, has played a key role in mitigating water scarcity pressure on Beijing via delivering sustainable and high-quality water yield, as well as water conservation services aimed at maintaining the ecological functions of the Capital Two Zones. However, the changing mechanism for both water yield and water conservation services instigated by the combined impacts of human activities and climate change remains poorly understood. In this study, we used the Integrated Valuation of Ecosystem Services and Trade-offs Tools (InVEST) model to analyze the changes in water yield and water conservation services, revealing the impacts of different land use scenarios. The results showed significant forest and impervious land area increment, while the water surface area decreased sharply from 1990 to 2020, with obvious urbanization expansion in ZJK during the period. Average annual water yield and water conservation from 1990 to 2020 were recorded at 48.98 mm and 2.35 mm, respectively. Precipitation emerged as the primary driver of water yield and conservation service changes, while the south of ZJK generally exhibited higher water yield and conservation service than the north of ZJK. Results also indicate that grassland had the highest water yield, with an average of 56.60 mm, followed by forest (55.66 mm) and shrub (55.07 mm). Further, the forest had the highest water conservation value (3.73 mm), followed by shrub (2.56 mm), and grassland (2.37 mm), respectively. The return of cropland to forest scenario had the most substantial decrease in water yield. Findings suggest that precipitation has a direct impact on water yield and conservation services via the amount of atmospheric water input, while land use alteration contributes to changes in regional-scale water. [ABSTRACT FROM AUTHOR]

Irrigation has become one of the main approaches to improve agricultural production in an arid area. The variation of soil moisture after irrigation has the potential to affect soil microbial community composition and soil organic carbon (SOC) storage, and thus, the imbalances in the terrestrial ecosystem carbon cycle. However, the impact of long‐term irrigation on the relationships between soil microbial community and SOC sequestration in semiarid agroecosystems is still poorly understood. We took advantage of a 7‐year irrigation experiment in a winter wheat‐maize rotation system in northern China, whereby the non‐irrigation was subject to rain‐fed conditions. We aimed to investigate the effects of long‐term irrigation on soil microbial communities and their linkages with soil carbon sequestration. Seven years of irrigation significantly increased soil moisture content by 39% but decreased SOC concentration of topsoil (0–20 cm) by 4.2% on average across all sampling times. The responses of soil microbial communities to irrigation were highly taxa dependent. Irrigation significantly decreased fungal biomass, fungal‐to‐bacterial ratio and Gram‐positive‐to‐Gram‐negative bacterial ratio, and did not affect the bacterial community biomass. The decreased SOC concentration under the long‐term irrigation was mainly caused by the changes in the ratio of fungi‐to‐bacteria. Our findings highlight the important role of soil fungal‐to‐bacterial ratio in mediating the response of SOC dynamics to a future drier climate in semiarid agricultural ecosystems. Highlights: Irrigation influences the soil microbial community and carbon stock in semiarid agroecosystems. Highlights the role of fungi:bacteria ratio in mediating the response of SOC dynamics to irrigation Long‐term irrigation decreased soil carbon content by changing the microbial community. Reduced SOC storage after irrigation was due to the decreased ratio between fungi and bacteria. [ABSTRACT FROM AUTHOR]

Land surface evapotranspiration (ET) plays an important role in energy and water balances. ET can significantly affect the runoff yield of a basin and the available water resources in mountainous areas. The existing models to estimate ET are typically applicable to plains, and excessive data are required to calculate the surface fluxes accurately. This study established a simple and practical model capable of depicting the surface fluxes, while using relatively less parameters. Considering the complex terrain, solar radiation was corrected by importing a series of topographic factors. The water deficit index, a measure of land surface wetness, was calculated by applying the f c (vegetation fractional cover) -Trad (land surface temperature) framework in the two-source trapezoid model for evapotranspiration model to mountainous areas after corrections of temperature based on altitude variations. The model was successfully applied to the Kaidu River Basin, a basin with few gauges located in the east Tien Shan Mountains of China. Based on the time scale extensions, ET was analyzed at different time scales from 2000 to 2013. The results demonstrated that the corrected solar radiation and water deficit index were reasonably distributed in space and that this model is applicable to ungauged catchments, such as the Kaidu River Basin. [ABSTRACT FROM AUTHOR]