Document Type : Original Article
Authors
1
MSc. Student, of Range Management, Faculty of Natural Resources, Yazd University, Yazd, Iran
2
Assistant Professor, Department of Geography, Yazd University, Yazd, Iran
Abstract
Drought with its effects on the performance of agricultural productions, water resources and vegetation cover accelerates the expansion of desertification. One of the methods for drought study and its devastating effects is monitoring and mapping of drought using meteorological indices and remote sensing techniques. To determine the impacts of drought on vegetation cover changes, the intensity of the drought was determined using the annual drought indices (i.e. the annual SPI and RDI). For drought indices mapping, five interpolation methods were used and compared. Then, the annual and seasonal average of NDVI was calculated using the MODIS 16-day NDVI time series from 2000 to 2014. The relationship between the drought indices (SPI and RDI) and the NDVI in different vegetation coverages was evaluated in Yazd province. According to the zoning of drought indices, Yazd province has been in a state of severe drought between 1999-2000 and 2007-2008. Evaluation of correlation results between different vegetation coverages type in Yazd province with drought indices showed that the semi-dense forests, woodlands, shrub-land, and pasture were severely affected by drought while the planting forests, agricultural areas, and gardens were less affected. Based on the results of coefficient of determination (R2) maps, the highest correlation between the average of NDVI in the spring and the annual drought index (SPI) was founded in the semi-dense forests, woodlands, shrub-land, and pastures grade 2 and 3 with the R2 of 57, 50, 44 and 41 percent, respectively. Likewise, in the summer, the semi-dense forests, pastures grade 1, 2, and 3, woodlands and shrubbery zones, had the R2 of 62, 51, 41, 35 and 44 percent, respectively.
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