Quantifying carbon sequestration in cultivated land ecosystems is essential for achieving carbon neutrality and ensuring food security, yet current models often fail to capture the complex interactions between crop phenology and environmental factors at regional scales. This paper proposed an improved CASA-CGC model that couples crop phenological parameters with photosynthetic physiological processes, enabling precise carbon sink accounting at the growth cycle scale of cultivated land ecosystems. Results indicate that the carbon sequestration capacity of cultivated land in the province significantly increased from 2010 to 2022, with an average increase of 163.04 g C m⁻², and the spatial pattern showed a centralized evolution characteristic. Model validation showed that the accuracy of the CASA-CGC model is significantly better than traditional methods. Compared with remote sensing inversion products and 93 ground measurement point data, the improved CASA-CGC model increased the R² by 0.155 and reduced the RMSE by 4.19 compared with the tr-CASA model. The innovative introduction of the GeoDetector model reveals that the nonlinear interaction between natural and human factors dominates the carbon sequestration process (accounting for 60%), with the interaction effect between altitude and cropping system configuration being the strongest (q = 0.312), confirming that humans can significantly amplify the potential of natural carbon sinks by optimizing cropping systems.

Cultivated land concentration and contiguity, as a core element of agricultural modernization development, holds strategic significance for enhancing agricultural production efficiency and ensuring national food security. This study employs vector patches as research units and classifies spatial connections between patches into direct and indirect connections. We quantify six types of spatial relationships between patches using binary encoding, enabling precise delineation of concentrated contiguous cultivated land. A Patch Connectivity Index is proposed. Combined with the Patch Area Index and Patch Shape Index, an evaluation system for cultivated land concentration and contiguity is established. Using Suixi County as a case study, we investigate the spatiotemporal evolution of its cultivated land concentration and contiguity from 2019 to 2023. Overall, patch connectivity exhibits a “single-element dominant, multi-element complementary” structural pattern, while the evaluation grading of cultivated land concentration and contiguity follows a normal distribution. Between 2019 and 2023, the average patch area decreased while the average number of connections between patches increased, indicating significant improvement in cultivated land concentration and contiguity levels. By adjusting spatial relationships between patches, the effective integration and utilization of cultivated land resources can provide theoretical foundations and practical references for agricultural modernization development.

The rapid expansion of agricultural activities on the Tibetan Plateau has raised concerns about soil degradation and nutrient dynamics in this ecologically fragile alpine region. However, existing studies lack a systematic quantification of the vertical influence depth of farmland utilization on soil nutrients and the relative importance of multiple environmental factors along their impact pathways. To address this gap, this study conducted extensive field soil sampling across southeastern Tibet and employed one-way ANOVA and structural equation modeling (SEM) to investigate the effects of farmland utilization (farm cropland vs. facility agriculture) and environmental factors (terrain, climate, soil properties, and human activities) on soil nutrients. The results showed that cultivated land use, particularly facility agriculture, significantly enhanced soil organic carbon, total nitrogen, total phosphorus, and the comprehensive nutrient index compared with natural vegetation, with values ranked as facility agriculture > farm cropland > natural vegetation, while total potassium remained insensitive to land use change. The influence of farmland utilization on soil nutrients was concentrated in the 0–30 cm plow layer, with the most pronounced effects in the 0–10 cm surface layer, whereas detectable but weaker effects extended to approximately 50 cm depth. Among environmental factors, elevation, land use intensity, mean annual temperature, and soil moisture were the dominant influencing factors. SEM further revealed that terrain and human activities had the strongest direct effects on soil nutrients (path coefficients of 0.54 and 0.41, respectively), whereas climate factors exhibited a negative direct effect (−0.31). Elevation-driven hydrothermal differentiation serves as the fundamental driver of soil nutrient variation, and land use patterns, especially facility agriculture, modulate this influence by altering local climate and soil properties. These findings provide a scientific basis for optimizing agricultural land management and sustaining soil fertility in high-altitude regions and offer quantitative insights into the pathways through which human activities and environmental factors interact to shape soil nutrient dynamics in alpine agroecosystems.

Cropland fragmentation remains a major constraint on agricultural mechanization, land consolidation, and cropland protection in hilly and mountainous regions. In terraced landscapes, cropland patches that appear close in planar space may nevertheless be difficult to connect because of steep slopes, terrain relief, gullies, and river networks. Conventional assessments based mainly on two-dimensional adjacency or patch size may therefore overestimate the relative suitability of cropland for spatially coordinated consolidation when terrain- and hydrology-related resistance is ignored. In this study, contiguous cropland consolidation potential is defined as a regional screening-level measure of the relative suitability of existing cropland patches for spatially coordinated consolidation, rather than as a comprehensive assessment of project-level land consolidation feasibility. Taking Huangzhong District, Xining City, China, as a case study, we developed a regional screening framework integrating cropland patch spatial characteristics, terrain–hydrological suitability, and resistance-based connectivity adjustment. Cropland evaluation units, defined as vector cropland patches, were independently derived from the 2025 Esri Sentinel-2 10 m Land Use/Land Cover Time Series product, while single-date Sentinel-2 imagery was used only for auxiliary visualization and cartographic presentation. The analysis followed a three-stage logic. First, cropland spatial characteristics and terrain–hydrological suitability were integrated using AHP–entropy weighting to estimate the initial regional consolidation suitability of each cropland unit. Second, relatively favorable cropland patches were identified as core sources, and minimum cumulative resistance analysis was used to quantify the resistance-based connection of each unit to the core-source network. Finally, the initial suitability was adjusted using the resulting resistance-based connectivity proxy to derive the final contiguous cropland consolidation potential index. The final assessment revealed clear spatial differentiation among the 1507 cropland evaluation units. Although the three potential classes contained similar numbers of patches, the high-potential class accounted for 88.285% of the total cropland area, indicating a strongly uneven area distribution among potential classes. High-potential areas were concentrated mainly in the north-central and south-central farming zones, where terrain conditions were relatively favorable and cumulative resistance was lower, whereas lower-potential units occurred more frequently in southern and marginal areas characterized by stronger terrain dissection and higher resistance. After resistance-based connectivity adjustment, 88.334% of the cropland area retained its original potential grade, while 10.733% was downgraded. This pattern indicates that the adjustment did not broadly overturn the initial assessment but mainly affected cropland units whose favorable patch–terrain conditions were offset by less favorable modeled connection to the core-source network. These findings demonstrate the value of distinguishing intrinsic patch–terrain suitability from resistance-based connection when screening contiguous cropland consolidation potential in hilly terraced regions.