Quantitative assessment of connectivity of forest patches in Caspian Sea catchment using landscape and graph theory indexes

The forests of the Caspian region are one of the most important forest resources in Iran, but what is seen as a large gap in research is the need to pay attention to the structural dimensions, especially to maintain the structural connectivity of these forests. The aim of this study was to assess and compare the indicators of forest landscape in the Caspian Sea watersheds. At first, the forest layer was extracted from the land cover map and 25 large watersheds were selected to study and compare the connectivity indicators. The connectivity of the terrestrial landscape was analyzed using landscaping metrics and graph theory indicators, by Fragstats and Conefor softwares respectively. Finally, by standardizing the calculated connectivity indicators, a final connectivity score was obtained for each watershed. The results showed that the indicators of forest patches connectivity in the whole Caspian catchment are very low, so that 80% of the watersheds are in the category of very low and low connectivity. Watershed 9 (Sardabroud, Shalmnroud) and 7 (Chalous) are in a very unfavorable situation, and only two watersheds of 14 (Chalav, Panjab) and 4 (Pasikhan), in the area of Chalav and Punjab, in the Haraz River, and the Shakharz, Pesikhan rivers, are in a better situation in terms of connectivity indicators. Considering the importance of preserving the structure and connectivity of forest patches, the results of this study show the need for special attention to the management and restoration programs of these forests.