Formerly managed forest reserves complement integrative management for biodiversity conservation in temperate European forests

In Central Europe, the predominant conservation strategy in forests is integrative management, seeking to balance economic interests with conservation goals. This is complemented by unmanaged strict forest reserves, most often small and with a history of forest management. Whether and how such reserves contribute to conservation when the surrounding forest is under progressive integrative management remains unclear. We compared forest structure and biodiversity of several taxa between formerly managed forest reserves and stands under progressive integrative management in beech and beech-oak forests. Alpha diversity was higher in reserves for birds and bats and higher in managed stands for plants and beetles, with no significant differences for fungi. Community composition differed between reserves and managed stands for plants, wood-decomposing fungi, beetles and birds. Reserves had 17 indicator species, including three red-listed species, and managed stands had 34, including one red-listed species. Diversity metrics differed between reserves and managed stands for both beech and beech-oak forests. Our results indicate that progressive integrative management and reserves, even when located in formerly managed stands, are complementary approaches benefitting different taxa and hosting partly different communities. Higher numbers of plants and beetles in managed stands were associated with higher light availability, as reserves in our study were undisturbed mature stands characterized by low light availability and low deadwood volumes. To benefit light and deadwood demanding species, new reserves should include early or late successional stands. If this is not feasible, restoration measures prior to designation or where possible under current protection status should be discussed.