Spatial and temporal analysis of the physiological state of Yatir forest with respect to drought years

Drought years are a very frequent phenomenon in Israel. Since 1995 Israel had suffered from three years of drought. Yatir, as a pine forest, is located on the border of the desert has suffered like other plants from the water shortage. The aim of this research was to detect and monitor the changes within the forest, during the growing season, and between the years. The use of the Normalized Vegetation Index NDVI to detect the state of a forest under stress has been applied in many studies. In the current study seven Landsat TM and ETM+ images along the past eight years were radiometricly, atmospherically and geometrically corrected. NDVI images were produced. In order to detect the changes along the years, eight change detection NDVI image differencing techniques were applied. The results indicated correlation between the photosynthetic activity along the growing cycle of the trees in one year (1994-1995) and NDVI dynamics. Also it was found that NDVI decreases between the year 1995 and 2000 due to drought events accruing along those years. The correlation between rainfall events and NDVI is a lag of one to two months. We concluded this study by stating that the Change Detection NDVI Image Differencing technique can be used not only to compare changes in cover types, but also to detect changes in the state of the same plant species.