Habitat loss of the chestnut-leaved oak (Quercus castaneifolia) in the Hyrcanian forests of Iran: impacts of anthropogenic factors on forest thinning and degradation

Abstract

Hyrcanian forests are a green belt of deciduous forests in the south of the Caspian Sea whose integrity and survival of its commercial species, such as the chestnut-leaved oak (Quercus castaneifolia), are at risk due to anthropogenic activities. This study performed coupled spatial-statistical modeling to identify the rate and determinants of Q. castaneifolia in parts of the forest landscape (5400 km2) in Mazandaran Province, Northern Iran. According to the Maximum Entropy model (MaxEnt), the species' most suitable habitats were small in area (9.03 % of the total forest cover of the region) and uneven in spatial distribution due to the prevailing effect of bioclimatic variables (Bios). Using object-based segmentation analysis, the oak’s suitable habitats were divided into spectrally and topographically homogenous areas as working units to search for their occurrence and rate thinning operations. The mean annual Landsat-NDVI of each unit was regressed against the year to use its slope as a measure of thinning, indicating that more than 80 % of the units experienced different thinning levels over the past two decades (2002–2022). Using the multiple linear regression model (p < 0.001), three anthropogenic factors, including road access, surface slope, and elevation, were positively linked to thinning levels, suggesting that the oak loss in the region might be anthropogenic in origin. Based on the results, forest managers and policymakers need to act more effectively and outline holistic conservation plans in the region.

Keywords

• Oak tree
• Maximum Entropy model
• Hyrcanian forests
• Habitat loss
• Road networks
• Object-based segmentation analysis