Document Type : Original Article
Department of Marine Meteorology & Physical Oceanography, Atmospheric Science & Meteorological Research Center
Department of surveying Engineering, Islamic Azad University, Taft Branch, Taft, Yazd, Iran
Iranian National Institute of Oceanography and Atmospheric Science
Aerospace Research Institute (Ministry of Science, Research and Technology)
In this research, the Spatio-temporal variability of vegetation growth was evaluated using Moderate Resolution Imaging Spectroradiometer (MODIS) Level 3 Enhanced Vegetation Index (EVI) at 1km resolution data products during 2003-2018 over Iran. The total variability, the amplitude of the annual phenological cycle, seasonal cycle peak, inter-annual variation, minimum level of variations, the timing of maximum vegetation, coefficient of variations, Sen's slope, Mann-Kendall and Hurst exponent indices were calculated as independent variables for all pixels. The results indicated that the variations of inter-annual cycles show a relatively stable trend, and relatively flat trend curves were observed for all types of vegetation in Iran. The seasonal phenological cycles were the most sources of intra-annual variations, and the maximum and minimum values were observed in mid-summer and early winter, respectively. The EVI peaks were observed in spring and summer and spatially have been distributed in 30.2% and 20.6% of the total areas. More than 44% of the total area showed stable vegetation coverages, and 1.7% of the total area showed a large amplitude of vegetation variations. About 89% of vegetated areas (37.7% of the total area) in the north, west, and southwest regions show improved sustainable variations with positive changes. The results show that about 5.5% of the vegetation coverage in the northeast and southwest was decreased. The presented analytical indices in this research are a cost-effective method for managing and predicting future environmental trends in developing regions at risk of desertification.