Monitoring of vegetation changes in Karaj watershed using NDVI index and gradient analysis

In the present study, vegetation changes in the Karaj watershed in 2006, 2011 and 2017 were investigated using the Normalized difference vegetation index (NDVI), the integration of land metrics and gradient analysis. After calculating the NDVI index, Then, two-section gradient analysis was designed in the direction of north-south and east-west. Then 6 metrics were calculated at two levels of class and landform using moving window design. The results of the comparison of the floor area showed that the highest increase in the area was done in lands with very good vegetation so that 5104 hectares (4%) have been enlarged. It is also the largest reduction in the area of excellent vegetation cover, which decreased by 4055 hectares (3%) during the studied period. The results of gradient analysis showed that the distribution pattern of vegetation in a three-year period is a cluster. The results of the analysis of both transects at the level of the land and the classes show that the average of mean distance from the nearest neighbor gradually increases during transects and the increase in total in 2017 compared to the initial year. This indicates an increase in the distance between the vertices of the same patch and the difficulty of communication between them, which is one of the signs of the disruption of the landscape.