Changes in live and deadwood pools in spruce-fir-beech forests after six decades of converting age class management to single-tree selection

Abstract

Forests and their management are changing due to new policies, land abandonment, decisions of forest owners, tenure and climate change. The importance of deadwood as species habitat in combination with increasing concerns for biodiversity is now broadly recognized and studies of deadwood are conducted in protection areas, plantations as well as natural commercial forests. One promising adaptive forest management alternative is plenter forest management. Here we attempt to answer questions, how stand structure changes after converting even-aged age-class forests into uneven-aged plenter forests and how the management transition affects deadwood pools, using an established pairwise comparison study in spruce-fir-beech forests in Austria. While live tree and branch volume were statistically different between the two treatments, deadwood volume and decay classes were comparable. Stands transforming into plenter forests exhibited clear unimodal stem density distribution in both 2009/10 and 2022, which differed from stands within a plenter equilibrium.. This indicates that structural transitions from age-class forests to plenter forests is a slow continuous process, requiring more than 60 years. Our results further suggest that plenter forests do not have higher deadwood stocks, despite considered “close-to-nature” management in some studies. Lower deadwood stocks in plenter forests (not significantly different to forests transitioning to plenter forests) may be compensated by plenter forests exhibiting a more diverse range of deadwood components, with possible positive overall effects on habitat value for species depending on deadwood of various decay classes.