Abstract
Abstract Schall et al. (2020) assessed how a combination of different forest management systems in managed forest landscapes dominated by European beech may affect the biodiversity (alpha, beta and gamma) of 14 taxonomic groups. Current forest policy and nature conservation often demand for combining uneven‐aged managed and unmanaged, set‐aside for nature conservation, beech forests in order to promote biodiversity. In contrast to this, Schall et al. (2020) found even‐aged shelterwood forests, represented by different developmental phases, to support highest regional (gamma) diversity. By pointing out that unmanaged forests included in our study are not old‐growth forests, Bruun and Heilmann‐Clausen (2021) challenge our conclusion as not providing sound scientific advice to societies. It is true that the studied unmanaged forests are not representing old‐growth forests as defined in the literature. However, we demonstrate the representativeness of our unmanaged forests for current beech forest landscapes of Central Europe, where managed forests were more or less recently set‐aside in order to develop old‐growth structures. We also show that the managed and recently unmanaged forests in our study already differ distinctively in their forest structures. We use this response to stress the role of forest reserves for promoting certain species groups, and to emphasise their importance as valuable research sites today and in the future. Synthesis and applications. We see two main conclusions from our study. First, unmanaged forests still matter. We agree with Bruun and Heilmann‐Clausen (2021) on the general importance of unmanaged, old‐growth or long‐untouched forests, and we do not question the importance of set‐aside forests for biodiversity conservation. However, a complete complementarity to managed systems may only reveal after many decades of natural development. Second, safeguarding biodiversity in largely managed forest landscapes should focus on providing a landscape matrix of different developmental phases with varying environmental conditions rather than on maximising the vertical structure within stands. Such landscapes can partly compensate for structures that are still missing in vital, dense and closed forests recently set‐aside or for unsuitable phases that may occur due to a cyclic synchronisation of forest structures in unmanaged forests.
Highlights
Schall et al (2020) investigated the biodiversity of 14 taxonomic groups in response to varying shares of three different forest management systems in ‘virtual forest landscapes’ of European beech
Two of these forest management systems have a long tradition in the study region: First, a traditional even-aged shelterwood system (EA) without clear-cuts and relying on natural regeneration where stands differ in developmental phase ranging from thickets to mature stands (Figure S1); second, uneven- aged selection forests where forest management operates on a fine spatial grain, creating vertically structured stands by selective logging of individual trees or small groups of trees (UEA, so-called ‘Buchen-Plenterwälder’, Figure S2)
As a mixed forest landscape of uneven-aged managed and unmanaged, set-aside forests is advocated by current forest policy and nature conservation, we were interested in how such a ‘virtual forest landscape composition’ would influence biodiversity in contrast to managed forest landscapes with varying shares of the coarse- grained EA shelterwood system
Summary
Schall et al (2020) investigated the biodiversity (alpha, beta and gamma diversity) of 14 taxonomic groups in response to varying shares of three different forest management systems (even-aged, uneven-aged and recently unmanaged forests) in ‘virtual forest landscapes’ of European beech. We agree that deadwood amounts of the unmanaged forests investigated by Schall et al (2020) are rather low (mean ± SD: 21.6 ± 13.5 m3/ha for all plots, 27.9 ± 13.3 m3/ ha within the World Heritage Site and 12.0 ± 6.7 m3/ha outside) This remains true when compared to the mean value of 64.9 ± 58.0 m3/ha reported by Vandekerkhove et al (2009) for beech forest reserves in Central Europe with a mean time span of non-intervention of 35 years. The values presented in Schall et al (2020) are low but not atypical for Central European unmanaged beech forests few decades after management abandonment
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