Peyman Mahmoudi - Department of Physical Geography, Faculty of Geography and Environmental Planning, University of Sistan and Baluchestan, Zahedan, Iran
Seyed Mahdi Amir Jahanshahi - Department of Statistics, Faculty of Mathematics, Statistics and Computer Science, University of Sistan and Baluchestan, Zahedan, Iran
Fatemeh Firoozi - Department of Remote Sensing and Geographical Information System (GIS), Faculty of Geography, University of Tehran, Tehran, Iran

In order to assess the vegetation changes trend of Sistan plain located in the eastern part of Iran,NDVI products from MODIS sensor on Terra satellite (MOD۱۳A۳) at ۱ km spatial resolution wereused over a ۱۵-year period (۲۰۰۰-۲۰۱۴) for three months of April, May and June. After obtainingimages from the land processes distributed active archive center, all ۴۵ images downloaded for thestudied area were mosaicked and geo-referenced to the Universal Transverse Mercator projectionsystem by nearest-neighbor resampling method. In the next step, the images were converted into anASCII format. By doing this, the total number of pixels within the studied area was ۳۰۰۸۰ pixels.Finally, the vegetation change trend was evaluated using Sen’s slope estimator nonparametric methodfor three-month of study and on a pixel scale. The results of this research showed that the highestincreasing changes trend in NDVI was observed in the northwest of the plain, and the highestdecreasing changes trend in NDVI was observed in the east and center of the plain. In addition,according to the results of this study, the use of Sen’s slope estimator nonparametric method in thestudies of vegetation coverage variation trend in arid regions resulting from NDVI products fromMODIS sensor can be very efficient and useful.

NDVI, MODIS Sensor, Trend, Sistan Plain, Sen’s Slope Estimator, Iran