Quantifying Climate Sensitivity of Apple Orchard Vigor Using Sentinel-2 NDVI and Lagged Meteorological Variables

Abstract

Understanding the extent to which short-term climatic variability regulates orchard canopy dynamics is essential for climate-responsive irrigation management in semi-arid regions. This study quantified intra-seasonal canopy vigor dynamics in a commercially managed, drip-irrigated apple orchard located in Niğde Province, Central Anatolia, Türkiye. Sentinel-2 surface reflectance imagery was processed to derive 15-day NDVI composites for the 2023 growing season, and monthly spatial NDVI maps were generated to evaluate intra-parcel heterogeneity. Concurrent meteorological data were aggregated into 15-day intervals, and lagged climatic variables were incorporated into a multiple linear regression framework. The regression model explained 74% of intra-seasonal NDVI variability (R²=0.74, p<0.001). Lagged mean air temperature exhibited a strong positive effect on canopy vigor (β=0.0131, p<0.001), whereas lagged solar radiation showed a statistically significant negative association (β=-0.0275, p=0.015). Model diagnostics indicated no substantial residual autocorrelation (Durbin Watson=1.66). Spatial analysis further revealed persistent intra-orchard heterogeneity despite uniform irrigation practices. Results demonstrate that even under continuous drip irrigation, canopy vigor dynamics remain strongly governed by atmospheric forcing. The integration of satellite-based vegetation monitoring with lagged climatic indicators provides a robust framework for evaluating orchard climate sensitivity and supporting adaptive irrigation scheduling. This approach contributes to sustainable water resource management in perennial fruit production systems under increasing climatic variability.