The effect of meteorological drought on vegetation dynamics in Iran

Drought as a complex ecosystem crisis can affect vegetation density and health. Iran with an arid and semi-arid climate is exposed to this phenomenon. Therefore, it is necessary to evaluate the effect of drought on vegetation. The purpose of this study is to evaluate the effect of meteorological drought on vegetation dynamics in Iran. In this regard, using MATLAB software, SPEI index with time scales of 3, 6, 9, and 12 months years was calculated and zoned for 99 meteorological stations with a statistical length of 30 years in Arc GIS software. In the next step, the highest value of EVI index per month was obtained from MOD13Q1 MODIS sensor product for the period 2001-2019. Then, using Terrset software, the correlation and slope of EVI index changes were calculated based on SPEI index changes. The results showed that in 18.46, 22.63, 30.77, and 28.14% of the total area of Iran, the SPEI of 3, 6, 9, and 12 months have the highest correlation with vegetation, respectively. The results of linear regression analysis showed that in Lut plain and the heights of Alborz and Zagros mountain ranges, the sensitivity of vegetation to meteorological drought is much lower and the slope of the line has been negative. While the central, southwestern, southeastern, and coastal areas of the Persian Gulf have a positive line slope and vegetation has shown great sensitivity to meteorological drought. According to the obtained results, it can be concluded that climatic conditions, topography, type of vegetation, geographical location, and human management are effective in determining the relationship between the two indicators of vegetation and drought. As a result, it is suggested that in future studies on the effect of climate change on vegetation, factors such as topography, land use, etc. should be considered in modeling.