Tree-Related Microhabitats: A Comparison of Managed and Unmanaged Oriental Beech–Dominated Forests in Northern Iran

Abstract

Abstract Tree-related microhabitats (TreMs) provide ecological niches in features for a variety of species in forests and are suitable indicators of biodiversity for certain taxa. The study objective was to compare the abundance and occurrence of TreMs in managed versus unmanaged Oriental beech (Fagus orientalis Lipsky) forests of northern Iran to quantify the effect of forest management on biodiversity indicators. We inventoried 3,954 trees to identify the number of trees with TreMs and quantify the occurrence of different types of TreMs. Managed forests averaged 25 trees with TreMs per hectare, and unmanaged forests averaged 41 trees with TreMs per hectare. In both forests, larger-diameter trees (≥50 centimeters diameter at breast height [dbh]) had more TreMs than smaller-diameter trees. TreMs were found on trees larger than a minimum size (32 centimeters dbh) and were more common on trees in poor health, as indicated by vitality class. According to our findings, managed forests have a lower diversity of TreMs than unmanaged forests. However, if management plans in deciduous forests include the retention of large-diameter trees during harvesting events, it is possible to balance providing TreMs within the forest while maintaining growth of economically valuable timber. Study Implications Forest biodiversity is time and labor intensive to quantify, and researchers have begun using tree-related microhabitats (TreMs) as a proxy for biodiversity. This study found TreMs occurred at lower abundances but had a similar occurrence of TreM groupings (cavities, injuries and wounds, deformation/growth form, and epiphytes) in managed Oriental beech (Fagus orientalis Lipsky) forests compared with unmanaged Oriental beech forests. Managed hardwood stands provided 25 TreMs per hectare, which is similar to numbers recommended for managing for biodiversity, and thus it may be possible to promote TreM creation and retention as an opportunity to increase forest biodiversity while also managing forests for timber production. Abundance of TreMs was associated with large-diameter trees and low-vitality trees (poor health). In deciduous forests managed for timber production, the retention of large-diameter trees is likely to align more closely with other management objectives than the retention of trees in poor health.