Temporal-Spatial Analysis of drought and Oak Trees Dieback of Zagros Forests in Ilam Province

One of the most important issues in the Zagros forests of Ilam is the dieback of oak trees, and the purpose of this research is to analyze the temporal-spatial analysis of the relationship between oak trees dieback and occurred droughts. In order to identify the dry areas of oak, using the method of determinationof. the training samples in geographic information system (GIS) and satellite images of modis were used. For temporal and spatial analysis of drought in Ilam province, NDVI index from MODIS satellite images in the statistical period of 2000 to 2018 was used. For  spatially analysis of relationship between oak forest dieback and droughts, Moran spatial autocorrelation model, one of the spatial pattern distribution models, was selected. Coincidentally, a 30-square-meter GPS device was used to find the coordinates of the dried droplets and the number of dried oak trees at each point, and a map of oak tree dieback distribution was prepared using GIS software. The results of combining drought zoning from NDVI index with oak dieback distribution map in two time series from 2000 to 2009 and 2010 to 2018 in the analysis of Moran index showed that oak dieback has a cluster pattern and the decline of oak trees is spreading in a mass. Also there was a significant relationship between drought trend in spatial and temporal dimensions and oak dieback in recent years in different parts of Ilam.