Volume 30, Issue 1 (spring 2026)
jwss 2026, 30(1): 1-12 |
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Chegini H, Komaki C B, Owneq M, Asgari H, Ghorbani K. Spatial-Temporal Correlation Analysis of Vegetation Health Index (VHI) with Climatic Variables (Case Study: Golestan Province). jwss 2026; 30 (1) :1-12
URL: http://jstnar.iut.ac.ir/article-1-4524-en.html
URL: http://jstnar.iut.ac.ir/article-1-4524-en.html
Department of Arid Zone Management, Faculty of Rangeland and Watershed Management, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. , komaki@gau.ac.ir
Abstract: (87 Views)
This study aimed to analyze the spatial–temporal correlation between the Vegetation Health Index (VHI) and climatic variables, including precipitation, potential evapotranspiration (PET), and mean temperature, in Golestan Province during the period 2000–2024. MODIS satellite products were used for vegetation and land surface temperature data, while the TerraClimate dataset provided precipitation and PET variables. After spatial–temporal alignment, the Cross-Correlation Function (CCF) was applied to identify optimal time lags, and the Random Forest model was employed to assess the relative importance of the climatic drivers. Turning to the results, increasing trends in mean temperature and PET were observed, alongside a significant decrease in precipitation, which led to intensified climatic stress and reduced VHI across the province, especially during summer in croplands and rangelands. The relationship between VHI and precipitation was positive (maximum correlation of 0.299 in croplands), negative with PET (−0.287), and non-linear with temperature (0.275). Notably, VHI responded to precipitation with short-term lags (0–1 month), whereas PET and temperature effects emerged with longer lags (2–4 months). The Random Forest analysis highlighted precipitation as the most influential factor on VHI, followed by PET and temperature, achieving strong predictive performance (R² = 0.78, RMSE = 0.09). Overall, these findings emphasize precipitation as the immediate driver of vegetation health, while PET and temperature act as secondary, cumulative stressors. The results provide valuable insights for developing climate adaptation and sustainable resource management strategies in agriculture and natural ecosystems of Golestan Province.
Keywords: Vegetation Health Index (VHI), Spatial– temporal correlation, Lag time, Random forest, Agricultural drought
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