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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. [ABSTRACT FROM AUTHOR]

Introduced pathogen microorganisms are important drivers of ecosystem change. This paper highlights the impact of the non-native pathogen mildew multi-species complex on the natural regeneration dynamics of pedunculate oak (Quercus robur). Pedunculate oak is a European keystone tree species, hosting a great amount of biodiversity, but its future role in (near-)natural forests is uncertain due to the lack of natural regeneration. We reviewed historical and recent ecological, pathological and forestry literature on topics related to the impact of mildew on the success of advanced natural regeneration of pedunculate oak in (near-)natural forests. We propose a novel hypothesis, the 'pathogen mildew hypothesis', to explain the failure of natural regeneration of pedunculate oak. Mildew reduces shade tolerance and vertical growth in seedlings and saplings, so sapling vitality and competitiveness have diminished considerably since it was unintentionally introduced to Europe in the early 20th century. Due to mildew infection, pedunculate oak in many cases no longer regenerates well naturally under its own canopy. We found that forest ecologists and conservationists often overlook the impacts of this 'recent' driver, while the 'closed-forest' and 'wood-pasture' hypotheses do not adequately help the management of pedunculate oak regeneration. Nature conservation and forest management plans should thus also consider the impact of mildew in order to improve natural regeneration, promote close-to-nature management of pedunculate oak forests, and support associated diversity. More generally, nature conservation, forest ecology and close-to-nature forestry should pay greater attention to the impact of introduced non-native microorganisms on the dynamics of natural ecosystems. Unlabelled Image • Ecologists and conservationists often overlook the impacts of alien microorganisms. • An alien microfungus impedes natural regeneration dynamics of a keystone species • Oak powdery mildew reduces shade tolerance and growth in seedlings and saplings. • Proposed hypothesis explains the failure of natural regeneration of pedunculate oak. • The alien microfungus threatens the rich biodiversity associated with oaks in Europe. [ABSTRACT FROM AUTHOR]

Retention forestry, which retains a portion of the original stand at the time of harvesting to maintain continuity of structural and compositional diversity, has been originally developed to mitigate the impacts of clear‐cutting. Retention of habitat trees and deadwood has since become common practice also in continuous‐cover forests of Central Europe. While the use of retention in these forests is plausible, the evidence base for its application is lacking, trade‐offs have not been quantified, it is not clear what support it receives from forest owners and other stakeholders and how it is best integrated into forest management practices. The Research Training Group ConFoBi (Conservation of Forest Biodiversity in Multiple‐use Landscapes of Central Europe) focusses on the effectiveness of retention forestry, combining ecological studies on forest biodiversity with social and economic studies of biodiversity conservation across multiple spatial scales. The aim of ConFoBi is to assess whether and how structural retention measures are appropriate for the conservation of forest biodiversity in uneven‐aged and selectively harvested continuous‐cover forests of temperate Europe. The study design is based on a pool of 135 plots (1 ha) distributed along gradients of forest connectivity and structure. The main objectives are (a) to investigate the effects of structural elements and landscape context on multiple taxa, including different trophic and functional groups, to evaluate the effectiveness of retention practices for biodiversity conservation; (b) to analyze how forest biodiversity conservation is perceived and practiced, and what costs and benefits it creates; and (c) to identify how biodiversity conservation can be effectively integrated in multi‐functional forest management. ConFoBi will quantify retention levels required across the landscape, as well as the socio‐economic prerequisites for their implementation by forest owners and managers. ConFoBi's research results will provide an evidence base for integrating biodiversity conservation into forest management in temperate forests. [ABSTRACT FROM AUTHOR]