Water resource management is crucial for sustainable agricultural and ecological development, particularly in regions with complex land-use patterns and sensitive eco-systems. The Bashang region of Zhangjiakou city, located in the agro-pastoral ecotone of northern China, is an ecologically fragile area that is currently undergoing significant land use and climate changes. Despite the importance of understanding the interplay between land use, climate change, and water conservation, few studies have comprehensively evaluated their combined effects on regional water resources. This study addresses this gap by investigating the spatiotemporal changes in the water yield (WY) and water conservation capacity (WCC) of the Bashang region under different land use and climate scenarios for the year 2035. This research employs the FLUS model to predict the future land use and the InVEST model to estimate the WY and WCC under a natural development scenario (NDS), an agricultural production scenario (APS), an ecological protection scenario (EPS), and a land planning scenario (LPS). The results reveal that the WCC is primarily influenced by precipitation, land use, and the topography. This study finds that scenarios which focus on ecological protection and land use optimization, such as the EPS and LPS, significantly enhance the water conservation capacity of the study region Notably, the LPS scenario, which limits urban expansion and increases the amount of ecological land, provides the best balance between the water yield and conservation. The findings highlight the need for integrated approaches to land use and water resource management, particularly in agro-pastoral transitional zones. The unique contribution of this research lies in its comprehensive modeling approach, which combines land use, climate data, and water resource analysis, and which provides valuable insights for sustainable land and water management strategies.

Water resource management is crucial for sustainable agricultural and ecological development, particularly in regions with complex land use patterns and sensitive eco-systems. The Bashang region of Zhangjiakou city, located in the agropastoral ecotone of northern China, is an ecologically fragile area undergoing significant land use and climate changes. Despite the importance of understanding the interplay between land use, climate change, and water conservation, few studies have comprehensively evaluated their combined effects on regional water resources. This study addresses this gap by investigating the spatiotemporal changes in water yield (WY) and water conservation capacity (WCC) under different land use and climate scenarios for the year 2035. The research employs the FLUS model to predict future land use and the InVEST model to estimate WY and WCC under Natural Development Scenario (NDS), Agricultural Production Scenario (APS), Ecological protection Scenario (EPS) and Land Planning Scenario (LPS). The results reveal that WCC is primarily influenced by precipitation, land use, and topography. The study finds that scenarios focusing on ecological protection and land use optimization, such as the EPS and LPS, significantly enhance water conservation capacity. Notably, the LPS scenario, which limits urban expansion and increases ecological land, provides the best balance between water yield and conservation. The findings highlight the need for integrated approaches to land use and water resource management, particularly in agro-pastoral transitional zones. The unique contribution of this research lies in its comprehensive modeling approach, combining land use, climate data, and water resource analysis, which provides valuable insights for sustainable land and water management strategies.

Soil degradation in the agro-pastoral ecotone of North China severely constrains the productivity of vital forage crops like oat (Avena sativa L.). While biochar and humic acid are known soil amendments, their combined synergistic effects and optimal application ratios remain poorly understood. This study aimed to investigate the integrated effects of biochar and humic acid on soil properties and oat productivity to identify an optimal co-application strategy for this fragile ecosystem. A two-year field experiment was conducted using a randomized complete block design. Treatments included a control (CK), sole biochar (B1H0), sole humic acid (B0H1), and three combined biochar-humic acid ratios (7:3, 5:5, and 3:7 by mass; B7H3, B5H5, B3H7). We measured key soil physicochemical and biological properties, as well as oat growth, forage yield, and quality parameters. Partial least squares structural equation modeling (PLS-SEM) was employed to elucidate the causal pathways linking amendments, soil quality, and crop performance. The combined application of biochar and humic acid demonstrated significant synergistic effects, outperforming sole applications in improving soil health and oat productivity. The B5H5 (1:1 ratio) treatment was the most effective, significantly reducing soil bulk density by up to 22.4% and increasing the mean weight diameter of water-stable aggregates by 40.7% compared to the CK. This treatment also led to the greatest increases in soil organic matter (68.9%), microbial biomass carbon (142.2%), and the activities of sucrase (139.8%) and urease. Consequently, the B5H5 treatment enhanced oat forage yield by 56.1% and improved its nutritional quality by reducing acid detergent fiber and neutral detergent fiber content by 22.9% and 12.7%, respectively. The PLS-SEM analysis confirmed that the positive effects of the amendments on crop performance were primarily mediated through the enhancement of soil quality (path coefficient β = 0.75, p < 0.001). The integrated application of biochar and humic acid, particularly at a 1:1 mass ratio, is a highly effective strategy for restoring degraded soils in the agro-pastoral ecotone. These findings provide a strong scientific basis for promoting this co-amendment approach as a sustainable solution to enhance agricultural resilience and productivity in fragile environments.

Soil degradation in the agro-pastoral ecotone of North China severely constrains the productivity of vital forage crops like oat (Avena sativa L.). While biochar and humic acid are known soil amendments, their combined synergistic effects and optimal application ratios remain poorly understood. This study aimed to investigate the integrated effects of biochar and humic acid on soil properties and oat productivity to identify an optimal co-application strategy for this fragile ecosystem. A three-year field experiment (2023–2025) was conducted using a randomized complete block design. Treatments included a control (CK), sole biochar (B1H0), sole humic acid (B0H1), and three combined biochar-humic acid ratios (7:3, 5:5, and 3:7 by mass; B7H3, B5H5, B3H7). We measured key soil physicochemical and biological properties, as well as oat growth, forage yield, and quality parameters. Partial least squares structural equation modeling (PLS-SEM) was employed to elucidate the causal pathways linking amendments, soil quality, and crop performance. The combined application of biochar and humic acid demonstrated significant synergistic effects, outperforming sole applications in improving soil health and oat productivity. The B5H5 (1:1 ratio) treatment was the most effective, significantly reducing soil bulk density by up to 22.4% and increasing the mean weight diameter of water-stable aggregates by 40.7% compared to the CK. This treatment also led to the greatest increases in soil organic matter (68.9%), microbial biomass carbon (142.2%), and the activities of sucrase (139.8%) and urease. Consequently, the B5H5 treatment enhanced oat forage yield by 56.1% and improved its nutritional quality by reducing acid detergent fiber and neutral detergent fiber content by 22.9% and 12.7%, respectively. The PLS-SEM analysis confirmed that the positive effects of the amendments on crop performance were primarily mediated through the enhancement of soil quality (path coefficient β = 0.75, p < 0.001). The integrated application of biochar and humic acid, particularly at a 1:1 mass ratio, is a highly effective strategy for restoring degraded soils in the agro-pastoral ecotone. These findings provide a strong scientific basis for promoting this co-amendment approach as a sustainable solution to enhance agricultural resilience and productivity in fragile environments.