Monitoring of Vegetation Cover change in Helen Forested Protected Area and its Causes based on Bi-temporal Analysis of NDVI

This paper aims to detect occurred changes in vegetation cover of forested Helen protected area using extracted NDVIs from Bi-temporal multispectral images of Landsat TM. To do so، at first forest areas with low and moderate density cover were identified and separated on land use map. Then preprocessing applications including radiometric corrections were done on both 1990 and 2009 images. Also for calculating NDVIs، data on 4th (near-infrared) and 2nd (red) bands were extracted from both images. Finally، changes in vegetation cover from 1990 to 2009 were calculated using NDVI of the study area. Results show that density has increased in 12. 4% of the study area including 7. 5% in moderate and 4. 9% in low density areas. Moreover، in 0. 63% of the total area vegetation density was decreased 0. 17% out of which belongs to forested area with moderate density and 0. 46% to low dense. Taking into account precipitation and temperature trends during this period، these results might be related to increasing long term annual temperature and winter seasonal precipitation، respectively. Also، considering this area as a protected area from 1992 and implementing more protective affairs can be related to these outcomes.