The ecological security pattern plays a crucial role in maintaining ecosystem health and ensuring ecological security. The establishment of the ecological security pattern in Mudanjiang City can provide a scientific basis and effective support for stabilizing the ecological environment, mitigating regional human–land conflicts, and rational land- use planning. This paper utilizes the theory of constructing an ecological security pattern using a source-resistance plane-corridor node to grade the importance of source areas based on the connectivity index. It combines morphological spatial pattern analysis and PLUS model to generate and identify the present value of 2022 in Mudanjiang City, as well as predict eight land types and seven landscape types under three development scenarios by 2032. A transfer matrix and transfer-intensity map are introduced to explore the structural characteristics of landscape transfer, while four fragmentation indexes are combined with principal component analysis and the coefficient of variation method to form comprehensive fragmentation indexes for different classes. Finally, based on constructing the ecological security pattern of Mudanjiang City in 2022, an analysis method is developed that establishes logical connections between land-use structure, a comprehensive fragmentation of land types, landscape transformation mechanism, and the importance of ecological sources. The results are as follows: (1) In Mudanjiang City, 23 ecological source areas, 65 corridors, and 66 ecological nodes were extracted. The overall ecological security pattern shows a “U” shape with openings to the northeast. (2) The cumulative weight of economic and social factors on the ecological resistance surface in Mudanjiang City reached 51.36%. (3) The response between the comprehensive fragmentation degree of forest land and the importance of primary and tertiary source areas was highly significant, with R values reaching 0.9675 and −0.8746, respectively. The comparative study comprehensively showed that the best scenario for the sustainable development of the ecological security pattern in the future is an ecological priority scenario, where the tertiary source area with the smallest area proportion but strongest disturbance fluctuation becomes a key area affecting connectivity and overall ecological security pattern in Mudanjiang City.

Climate change is reshaping yield formation and water use in cold-region rice production through rising air temperatures, altered precipitation patterns, and increasing atmospheric CO₂ concentrations. However, the responses of yield, crop evapotranspiration (ET_c), and water use efficiency (WUE) to climate forcing and elevated CO₂ remain insufficiently quantified for cold-region rice systems in Northeast China. This study simulated changes in rice yield, ET_c and WUE during the 2030s–2090s relative to the 2000–2020 baseline period under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios at 10 agro-meteorological stations in Heilongjiang Province. Simulations were conducted using the AquaCrop model driven by CMIP6 multi-model climate data, and the contribution of elevated CO₂ was quantified by comparing the rising-CO₂ and fixed-CO₂ treatments. The results showed that under SSP5-8.5, the maximum air temperature in the 2090s is projected to increase by 5~6 °C relative to the baseline period, while precipitation is projected to range from −10% to 20%. Compared with the fixed-CO₂ treatment, rice yield under the rising-CO₂ treatment is projected to increase by 18.70%. Although ET_c showed an overall increasing trend, rising CO₂ attenuated its increase. Under SSP5-8.5 in the 2090s, ET_c increased by only 2.70% under rising-CO₂ treatment, compared with 11.61% under fixed-CO₂ treatment. As a result of increased yield and ET_c, the WUE improved by 15.42% and 14.28% under SSP2-4.5 and SSP5-8.5, respectively, in the 2090s, whereas it remained below the baseline level under the scenarios without CO₂ effects. These findings indicate that rising CO₂ may enhance yield and moderate ET_c increases, thereby providing useful information for regional grain-yield assessment, agricultural water-resource evaluation, and climate-change adaptation planning.