INTEGRATED ASSESSMENT OF CLIMATE CHANGE IMPACTS ON WATER RESOURCES, CROP DEVELOPMENT, AND ECOSYSTEM SERVICES IN IRRIGATED AGRICULTURAL SYSTEMS OF TASHKENT REGION, UZBEKISTAN

Climate change poses compounding threats to agricultural systems in Central Asia, simultaneously affecting water availability, crop productivity, and soil-mediated ecosystem services. This study presents the first integrated, model-based assessment of these three interconnected dimensions for irrigated wheat (Triticum aestivum L.) production in Tashkent region, Uzbekistan. We applied the DSSAT-CERES-Wheat process-based crop model, an AquaCrop-based water balance framework, and the InVEST ecosystem service assessment tool, driven by historical secondary data (1990-2020) and CMIP6 climate projections under SSP2-4.5 and SSP5-8.5 emission scenarios across three future time horizons (2025-2040, 2041-2070, 2071-2099). Model calibration and validation against FAOSTAT, Uzstat, and NASA POWER data yielded good to excellent performance (R2 = 0.83-0.91; nRMSE < 15%) across all output variables. Results indicate that rising temperatures will progressively increase seasonal irrigation water demand by 6-28% while simultaneously shortening the growing season and reducing grain yield by up to 28.7% under the long-term high-emission scenario. Soil organic carbon stocks and composite soil quality indices are projected to decline by 9.8% and 22.1%, respectively, by the late 21st century, undermining nutrient cycling, water regulation, and provisioning ecosystem services. Sensitivity analysis reveals that temperature increase is the dominant driver (accounting for 65-72% of total change), followed by precipitation reduction (18-24%) and elevated CO2 compensation (8-14%). These compounding impacts create a self-reinforcing degradation spiral: reduced soil quality diminishes crop resilience, which increases water demand, which further stresses soils. We propose an integrated adaptation framework including adjusted sowing calendars, deficit irrigation scheduling, conservation tillage, and organic matter management as priority strategies to sustain wheat productivity and ecosystem service delivery under future climate conditions in the Tashkent region.气候变化对中亚农业系统构成多重复合威胁，同时影响水资源可获得性、作物生产力以及以土壤为媒介的生态系统服务。本研究首次针对乌兹别克斯坦塔什干地区的灌溉小麦（普通小麦*Triticum aestivum* L.）生产，对这三个相互关联的维度开展了基于模型的综合评估。本研究采用了DSSAT-CERES-Wheat过程作物模型、基于AquaCrop的水平衡框架以及InVEST生态系统服务评估工具，所用驱动数据为1990-2020年的历史二手数据，以及第六次耦合模式比较计划（CMIP6）在SSP2-4.5与SSP5-8.5两种排放情景下的气候预估数据，覆盖三个未来时间区间：2025-2040年、2041-2070年、2071-2099年。基于粮农组织统计数据库（FAOSTAT）、乌兹别克斯坦国家统计委员会（Uzstat）以及NASA POWER数据开展的模型校准与验证结果显示，所有输出变量的表现均达到良好至优秀水平（决定系数R²=0.83~0.91；归一化均方根误差nRMSE<15%）。研究结果表明，在长期高排放情景下，气温上升将逐步使季均灌溉需水量增加6%~28%，同时缩短作物生育期，并使籽粒产量最高降低28.7%。至21世纪末，土壤有机碳储量与综合土壤质量指数预计将分别下降9.8%与22.1%，进而破坏养分循环、水分调节与供给型生态系统服务。敏感性分析结果显示，气温升高是主导驱动因素（贡献了总变化量的65%~72%），其次是降水减少（18%~24%）与CO₂浓度升高的补偿效应（8%~14%）。这些复合影响形成了自我强化的退化循环：土壤质量下降会削弱作物抗逆性，进而增加灌溉需水量，进一步加剧土壤压力。本研究提出了一套综合适应框架，包括调整播种期、亏缺灌溉调度、保护性耕作与有机质管理等优先策略，以在未来气候条件下维持塔什干地区的小麦生产力与生态系统服务供给能力。