UAV-Based Assessment of Pre- and Post-Harvest Water Stress Dynamics in Vineyards Using NDRE and GNDVI Spectral Responses

Abstract

Abstract Climate change and increasing drought frequency are intensifying water stress risks in viticultural systems, particularly in semi-arid regions where water availability directly influences grapevine productivity and quality. This study investigated pre-harvest and post-harvest water stress dynamics in a commercial Ağın Beyazı vineyard located in Eastern Türkiye using UAV-based multispectral imagery. High-resolution orthomosaics (2.31 cm pixel⁻¹) were acquired with a DJI Mavic 3 Multispectral platform and used to generate Green Normalized Difference Vegetation Index (GNDVI) and Normalized Difference Red Edge Index (NDRE) maps for both phenological periods. Water stress responses were evaluated through pixel-based change detection, descriptive statistics, spatial heterogeneity metrics (Local Mean and Local Standard Deviation), and Global Moran’s I spatial autocorrelation analysis. Results revealed measurable spectral differences between pre-harvest and post-harvest periods, indicating changes in canopy physiological activity associated with water stress and post-harvest vine responses. GNDVI exhibited a higher relative change (+ 10.49%) and stronger standardized response ratio, suggesting greater sensitivity to overall canopy vigor and photosynthetic activity. In contrast, NDRE showed the highest heterogeneity response (+ 64.97%), demonstrating superior capability for identifying localized stress variability and fine-scale physiological differences within the vineyard. Spatial heterogeneity analyses indicated increasing local variability after harvest, while consistently positive Moran’s I values (≈ 0.257) revealed that stress patterns remained spatially organized rather than randomly distributed. These findings suggest that vineyard water stress is controlled not only by vine physiology but also by persistent spatial factors such as soil conditions, micro-topography, and water availability. Overall, the combined use of GNDVI and NDRE provided complementary information for vineyard water stress assessment. The proposed framework demonstrates the potential of UAV-based multispectral monitoring for precision irrigation management, early stress detection, and climate-resilient viticulture in water-limited environments.

Plant phenotyping relevance

UAVマルチスペクトル画像からGNDVI・NDREを抽出し、ブドウ樹の水ストレスと空間変動を評価する測定・解析フレームワークが研究の中心である。

Code and data availability

The article describes UAV multispectral imagery acquisition (DJI Mavic 3 Multispectral) and GNDVI/NDRE analyses for a vineyard in Türkiye, but contains no data availability statement, no public repository deposit, no author code/scripts, and no supplement reference. All URLs in the text are citations to prior work, not

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