Earthworm Communities in Natural and Reforestation Areas of the Hyrcanian Forest; A Conservation Approach

Introduction: The Caspian Hyrcanian forests are a habitat with ancient growth of temperate broadleaf trees that spread along the Alborz Mountain range's northern slopes and near the southern borders of the Caspian Sea. However, human activities have significantly reduced forest cover, and identifying species diversity, forest structure, and human manipulations in Hyrcanian forests have received less attention. Macroinvertebrates are the main part of soil biodiversity in forests. Earthworms are one of the main components of soil biodiversity in forests and are one of the most valuable indicators of soil health and a vital component of soil fauna. Nevertheless, studying earthworms based on their morphological features poses various challenges. To overcome these challenges, DNA barcoding has emerged as a valuable tool extensively employed in biodiversity research. The study aims to use molecular approaches to identify earthworms and their diversity and compare the communities of these animals between natural and planted forests in the Hyrcanian region.Materials and Methods: The study was conducted in the central part of the Caspian Hyrcanian forests. The research was done in three locations, with two planted and two natural areas in each location. Within each area, a total of six quadrats were randomly placed to collect samples. Subsequently, the samples were classified based on their morphological characteristics. A total of 251 earthworm samples were collected, and 22 individuals were then selected for genetic studies using the cytochrome c oxidase subunit one (COI) gene after doing morphological sorting. The samples were initially kept in 96% ethanol for genetic studies to long-term storage. Univariate and multivariate statistical analyses were then performed to investigate the diversity of earthworms and compare their communities between planted and natural areas and three locations. Results: Based on genetic studies, 15 taxonomic units of earthworm were identified in the study area of the Hyrcanian forests. The research findings indicate that the abundance and total number of Operational Taxonomic Units (OTUs) in natural and planted areas are almost the same. The results of univariate statistical analysis (ANOVA) and multivariate analysis (PERMANOVA) did not show any significant difference for earthworms between natural and planted habitats.Discussion: The study demonstrates that the utilization of barcoding techniques yields more accurate results; however, the establishment of a comprehensive DNA reference library is necessary to enhance the precision of species classification. Despite finding no significant differences in earthworm communities between natural and planted forests, notable distinctions were detected among the three studied locations. This suggests that the dependence of earthworms on planted forests is contingent upon specific characteristics, soil conditions, and management practices. Moreover, the results show that earthworms are known for their ability to adapt to a wide range of environments. It is anticipated that secondary forests, which have been established for over two decades, will provide sufficient time for the restoration of earthworm populations, contributing to overall ecosystem recovery. The significance of this knowledge lies in its contribution to the sustainable preservation and effective administration of forests, particularly the Hyrcanian forests, which represent an ancient and invaluable ecosystem.