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.