An Approach for Quantifying the Spatial Disturbance Variations Based on Landscape Metrics (Case Study: Arasbaran Protected Area during 1990-2014)

The disturbance, is the result of the landscape conversion into smaller pieces with less communication, which in turn leads to decrease the ecosystem stability. The aim of this study is to introduce a new method for quantifying the spatial disturbances of forested areas, which is the main land-cover class of Arasbaran Protected Area, using the landscape metrics over a period of time. To do so, the Landsat satellite imagery were used to generate the land-cover maps of corresponding years (i.e. 1990 and 2014). The metric graph analyses were applied to determine the optimal size of the zones for ten random points in the land-cover map of 2014. Optimal size was determined by plotting the curve results for different areas. Different metrics, i.e. shape, size, number, density, distribution, and contiguous metrics were calculated to quantify the landscape components. To standardize the metric values the standard deviation method was applied. PCA analysis to group the effective metrics on disturbance based on their eigenvalues. Then, the disturbance maps were generated for each time, based on the loading value of each metric. According to the results in both periods, the highest disturbance (high disturbance class) was observed around residential and agricultural areas, and the least disturbance was occurred in mountainous and inaccessible areas, that mostly covered by continuous and dense forests. The results showed that the disturbance rate was increased in 2014 and the land-cover change from forest to grassland has the highest contribution in the increasing disturbance rate with an area of 170.24 hectares. The presented method can also be used in the assessment, planning and management of other specific ecological zones.