Remote sensing analysis of the extent and severity of oak decline in Malekshahi city, Ilam, Iran

Abstract

The Zagros mountain forests in Iran, constitutes approximately 40 percent of the country's forests expanding in eleven provinces, provides important functions as soil and water preservation. The forestes sustained severe oak decline in places over the last decade, triggered by chain factors such as drought, pathogens and Borer beetles. Determining the extent of the declined regions is the first step to address manage and address the risk posed by such environmental hazards. In this research, we focus on Malekshahi city in Ilam province and use Landsat satellite images in years between 2000 and 2015 for determining spatial pattern of oak decline in this region. Slope of temporal variation of an appropriate vegetation index and a water index, are extracted and analyzed from Landsat imageries. The oak forests are classified in three categories: Healthy forests, lowseverity declined forests, and high-severity declined forests, based on EVI and NDWI. According to the results, approximately 16%, 58% and 26% of the region belongs to healthy regions, low and high level of disease, respectively. Finally, the overall accuracy of the oak decline map, is evaluated based on available ground truth data. About %83 overall accuracy, shows high performance of the proposed method in detecting declined regions against healthy ones. But it has less ability in classifying different levels of decline, since overall acccuracy is about %54 for this purpose.

Trend Analysis of Soil Salinity in Different Land Cover Types Using Landsat Time Series Data (Case Study Bakhtegan Salt Lake)

“…In this study, the slope of temporal variation of five appropriate vegetation indices was extracted and the Oak forests were classified into four categories according to the severity of Oak decline. The results of this study showed that the EVI index had the best performance between selected vegetation indices (Imanyfar and Hasanlou, 2017). Gorji et al assessed soil salinity changes in the vicinity of Tuz Salt Lake region in Turkey using multi-temporal Landsat-5 and Landsat-8 images obtained between 1990 and 2015.…”