Monitoring the decline of Persian oak in Iran using remote sensing – Case study of Basht forest

Abstract

Oak forest decline is a complex problem that it has started for a long time ago in the world. This problem is widelyspread because of lacking of efficient and reliable facilitiesfor monitoring these forests. In this research, the pattern of spatial-temporal distribution and decline of Iranian Oak stands in the Bashtforest wasmonitored using remote sensing. The area of study is located in the provinces of Kohgilouyeh and Boyer Ahmad in Iran. After selecting the study area,forest visitswere carried out and samples of dead trees were collected. Based ontheoak crown declineattack, the forest wasdivided into four categories: low (crown dieback 20-0 percent), medium (between 40-20% of crown dieback), high (between 60-40%) and severe (more than 60% crown dieback). The geographical locations of the harvested trees wererecorded using global positioning system (GPS). In order to determine the most appropriate vegetation index, root mean square error (RMSE) for 12 vegetation indiceswere calculated from Landsat 8 images. The results of this study provedthat ratio vegetation index (RVI) indicator with the lowest RMSE wasanappropriatetoolfor assessing the status of the Iranian Oak forests. Finally,in order to study temporal changes of the Oak forests,dieback canopy variance and RVI for 6 years(1987, 2000, 2003, 2009, 2013 and 2014) were computed from different Landsat images. The computed indices indicatedthat crown freshness witnessedsignificantand continuous decrease.