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Old-growth forests (OGF) provide valuable ecosystem services such as habitat provision, carbon sequestration or recreation maintaining biodiversity, carbon storage, or human well-being. Long-term human pressure caused OGFs in Europe to be rare and scattered. Their detailed extent and current status are largely unknown. This review aims to identify potential methods to map temperate old-growth forests (tOGF) by remote sensing (RS) technology, highlights the potentials and benefits, and identifies main knowledge gaps requesting further research. RS offers a wide range of data and methods to map forests and their properties, applicable from local to continental scale. We structured existing mapping approaches in three main groups. First, parameter-based approaches, which are based on forest parameters and usually applied on local to regional scale using detailed data, often from airborne laser scanning (ALS). Second, direct approaches, usually employing machine learning algorithms to generate information from RS data, with high potential for large-area mapping but so far lacking operational applications and related sound accuracy assessment. Finally, indirect approaches integrating various existing data sets to predict OGF existence. These approaches have also been used for large area mapping with a main drawback of missing physical evidence of the identified areas to really hold OGFs as compared to the likelihood of OGF existence. In conclusion, studies dealing with the mapping of OGF using remote sensing are quite limited, but there is a huge amount of knowledge from other forestry-related applications that is yet to be leveraged for OGF identification. We discuss two scenarios, where different data and approaches are suitable, recognizing that one single system cannot serve all potential needs. These may be hot spot identification, detailed area delineation, or status assessment. Further, we pledge for a combined method to overcome the identified limitations of the individual approaches.

Many studies have investigated how spring temperature affects laying dates and how this in turn affects the synchrony between nestling food demands and the insect food peak that follows tree budburst. While there is strong evidence that temperature itself acts as a cue for this plasticity in annual timing, the exact nature of the cue and response remains to be elucidated. Here we use long-term data on Great and Blue Tits and an unprecedented dataset on the location and phenology of 1396 trees to investigate whether small-scale variation in laying date can be explained by local tree phenology, and/or by tree species composition around nestboxes. Individual trees maintained their relative timing of budburst between years, while differences among tree species were more variable between springs. Contrary to expectation, we found no relation between first-egg dates and average budburst date at different distances around the nestbox. This can at least partly be explained by the very low degree of spatial autocorrelation in tree budburst. We did find an effect of local tree composition whereby Blue Tits, but not Great Tits, laid earlier in nestboxes surrounded by more oaks and fewer beeches. Although Blue Tit nest failure rate was higher in territories with more beech trees, independently of laying date, we found no evidence for preferential occupation of oak-dominated territories. Thus although we found some evidence for fine-scale effects of tree species on timing of breeding, the underlying mechanism remains unclear.

Europe has a history rich in examples of successful and less successful introductions of non-native trees (NNT) - trees with an evolutionary origin outside of Europe. NNT have been introduced for various reasons such as ornamental purposes, food production, land reclamation/amelioration and timber production. The use of NNT also causes controversies due to potential negative impacts on natural ecosystems of NNT that become invasive. Many international legal frameworks responded to the presence and use of NNT, such as international treaties and conventions ; and also the European Union deals with the issue of invasive alien species in Regulation (EU) No. 1143/2014. However, especially the national and regional responses to NNT affect current and future management decisions in the forest sector and furthermore shape forest landscapes of Europe. In this comprehensive study of the legal landscape concerning NNT we identified all relevant legislations, the different legal approaches and the regulatory intensity in every European country (except microstates). Hard and relevant soft law items at the national and sub-national (regional) level for 40 European countries were collected and proofed using a targeted questionnaire sent to country experts across Europe mainly coming from the forestry and nature conservation sector. In addition, international and national legislation information systems and databases were consulted to complete the information. Legislations included updates until June/July 2019. In total, 320 national and regional law items were identified to be relevant for the regulation of NNT in the investigated 116 legislative units (countries, and regions with own legislation) in Europe. Countries and regions were empirically categorised according to ad hoc created legislation indicators dealing with the general ban of introduction of non-native species, the generally allowed and prohibited NNT, approval mechanisms, e.g. mandatory forest management plans, and areas and cases where NNT are restricted or completely prohibited. Our study revealed a very diverse legal landscape in Europe, with a large variety of approaches being pursued to regulate NNT, and the intensity of regulation ranging from very little restrictions on the species choice and plantation surface area to a complete ban of NNT in forests.

Forests host most terrestrial biodiversity and their sustainable management is crucial to halt biodiversity loss. Although scientific evidence indicates that sustainable forest management (SFM) should be assessed by monitoring multi-taxon biodiversity, most current SFM criteria and indicators account only for trees or consider indirect biodiversity proxies. Several projects performed multi-taxon sampling to investigate the effects of forest management on biodiversity, but the large variability of their sampling approaches hampers the identification of general trends, and limits broad-scale inference for designing SFM. Here we address the need of common sampling protocols for forest structure and multi-taxon biodiversity to be used at broad spatial scales. We established a network of researchers involved in 41 projects on forest multi-taxon biodiversity across 13 European countries. The network data structure comprised the assessment of at least three taxa, and the measurement of forest stand structure in the same plots or stands. We mapped the sampling approaches to multi-taxon biodiversity, standing trees and deadwood, and used this overview to provide operational answers to two simple, yet crucial, questions: what to sample? How to sample? The most commonly sampled taxonomic groups are vascular plants (83% of datasets), beetles (80%), lichens (66%), birds (66%), fungi (61%), bryophytes (49%). They cover different forest structures and habitats, with a limited focus on soil, litter and forest canopy. Notwithstanding the common goal of assessing forest management effects on biodiversity, sampling approaches differed widely within and among taxonomic groups. Differences derive from sampling units (plots size, use of stand vs. plot scale), and from the focus on different substrates or functional groups of organisms. Sampling methods for standing trees and lying deadwood were relatively homogeneous and focused on volume calculations, but with a great variability in sampling units and diameter thresholds. We developed a handbook of sampling methods (SI 3) aimed at the greatest possible comparability across taxonomic groups and studies as a basis for European-wide biodiversity monitoring programs, robust understanding of biodiversity response to forest structure and management, and the identification of direct indicators of SFM., This review was funded by the EU Framework Programme Horizon 2020 through the COST Association: COST Action CA18207: BOTTOMSUP- Biodiversity Of Temperate forest Taxa Orienting Management Sustainability by Unifying Perspectives.

Aims: Primary forests are critical for forest biodiversity and provide key ecosystem services. In Europe, these forests are particularly scarce and it is unclear whether they are sufficiently protected. Here we aim to: (a) understand whether extant primary forests are representative of the range of naturally occurring forest types, (b) identify forest types which host enough primary forest under strict protection to meet conservation targets and (c) highlight areas where restoration is needed and feasible. Location: Europe. Methods: We combined a unique geodatabase of primary forests with maps of forest cover, potential natural vegetation, biogeographic regions and protected areas to quantify the proportion of extant primary forest across Europe's forest types and to identify gaps in protection. Using spatial predictions of primary forest locations to account for underreporting of primary forests, we then highlighted areas where restoration could complement protection. Results: We found a substantial bias in primary forest distribution across forest types. Of the 54 forest types we assessed, six had no primary forest at all, and in two-thirds of forest types, less than 1% of forest was primary. Even if generally protected, only ten forest types had more than half of their primary forests strictly protected. Protecting all documented primary forests requires expanding the protected area networks by 1,132km2 (19,194km2 when including also predicted primary forests). Encouragingly, large areas of non-primary forest existed inside protected areas for most types, thus presenting restoration opportunities. Main conclusion: Europe's primary forests are in a perilous state, as also acknowledged by EU's “Biodiversity Strategy for 2030.” Yet, there are considerable opportunities for ensuring better protection and restoring primary forest structure, composition and functioning, at least partially. We advocate integrated policy reforms that explicitly account for the irreplaceable nature of primary forests and ramp up protection and restoration efforts alike.

The geographical distributions of species associated with European temperate broadleaf forests have been significantly influenced by glacial–interglacial cycles. During glacial periods, these species persisted in Mediterranean and extra-Mediterranean refugia and later, during interglacial periods, expanded northwards. The widespread saproxylic beetle Bolitophagus reticulatus depends closely on European temperate broadleaf forests. It usually develops in the tinder fungus Fomes fomentarius, a major decomposer of broadleaf-wood. We sampled B. reticulatus in sporocarps from European beech (Fagus sylvatica) and Oriental beech (Fagus orientalis) across Europe and the Caucasus region. We analysed mitochondrial gene sequences (cox1, cox2, cob) and 17 microsatellites to reconstruct the geographical distribution of glacial refugia and postglacial recolonization pathways. We found only marginal genetic differentiation of B. reticulatus, except for a significant split between populations of the Caucasus region and Europe. This indicates the existence of past refugia south of the Great Caucasus, and a contact zone with European populations in the Crimean region. Further potential refugia might have been located at the foothills of the Pyrenees and in the Balkan region. Our genetic data suggest a phalanx-wise recolonization of Europe, a reflection of the high mobility of B. reticulatus.

We studied the effect of coarse woody debris (CWD) on the soil nutrient status in two beech (Fagus sylvatica) dominated forest reserves in Flanders, Belgium: Wijnendale Forest, on a sandy soil and Kersselaerspleyn in Sonian Forest, on a loamy soil. More specifically, we looked at the chemical composition of beech logs of different stages of decay. In addition, we examined the chemical composition of the organic and the mineral soil at five distances from the decomposing logs. We considered the concentrations of the following elements: C, N, P, S, Ca, K, Mg, Mn, Fe, and Al. The results indicate a difference in wood and soil chemical composition between the two forest sites. The soil and the aboveground biomass of Wijnendale had the highest total N concentration and the lowest concentrations of P and base elements (Ca, K, Mg, and Mn). There is an increase in element concentrations in CWD of both forests during the decomposition, except for K and C. The higher N concentration in Wijnendale, explained by high atmospheric nitrogen deposition in this forest, persisted during decomposition. By contrast, the concentrations of P, Ca, K, and Mg in dead wood of both forests became similar when decomposition proceeded. The effect of CWD was more pronounced in the organic soil layer than in the mineral soil. The organic soil in the proximity of CWD had a higher pH and higher concentrations of C, N, P, Ca, Mg, and Mn (in Sonian forest) and a lower Al concentration (in Wijnendale forest) and this is highly significant for Ca, a limiting nutrient in moderate to highly acidic forests. The percentage of the soil surface impacted by the logs is 0.92% and 0.36% for Sonian and Wijnendale respectively, which is expected to increase with time, considering the fact that both reserves are only recently left unmanaged. The results of this study highlight the contribution of CWD in sustaining the nutrient status and buffering capacity of forest sites, in particular on soils sensitive to acidification and exposed to high nitrogen deposition.

Successful colonization of empty habitat patches depends both on the capacity of a species to reach the patch and its ability to establish and persist. Getting better insights into the various factors that affect colonization success is especially relevant in the context of restoration projects that aim at restoring biodiversity in newly created habitats like afforestation. While it is generally known that soil microbial communities play a key role in forest ecosystems, it remains largely unknown how they recover in recently restored forests on former agricultural land. Here, we used next-generation sequencing to investigate how spatial isolation and abiotic conditions affected the diversity and composition of ectomycorrhizal fungal communities in recent forest stands. Soil samples and roots of Quercus robur were sampled in ancient forest stands and recent stands both adjacent and spatially isolated from the ancient stands. Our results showed that ectomycorrhizal fungal community composition was affected by a combination of isolation and local soil conditions. Although communities of recently restored forest stands more resembled those of ancient stands when they immediately bordered ancient forest, there were still significant differences in community composition, most likely as a result of differences in edaphic conditions. Isolated stands had a significantly lower diversity and were mainly colonized by highly dispersive species. Overall, these results indicate that ectomycorrhizal fungal communities may develop faster in recent forest stands connected to ancient forest than in isolated stands, and that isolated stands may remain impoverished for many decades or even for indeterminate time. keywords: Dispersal limitation, Colonization, Ectomycorrhizal fungi, Forest restoration ispartof: Forest Ecology and Management vol:429 pages:84-92 status: published

The study of charcoal production pits (pit kilns), excavated in central Belgium, provides information on Early and High Medieval woodland dynamics and human impact on the forest composition in the Northwest-European Lowland. Radiocarbon dating of charcoal recovered from the kilns demonstrates two different phases of charcoal production, one during the Early Medieval period (c. 650 AD-950 AD) and one during the High Medieval period (c. 1040 AD-1260 AD). Charcoal identification shows that the Early Medieval kilns are dominated by beech (Fagus sylvatica) while the younger kilns are dominated by oak (Quercus sp.), indicating a shift in woodland composition. This shift is likely to be a consequence of the earliest charcoal production activities, which resulted in the degradation of the primeval beech-dominated forest to a secondary forest dominated by oak, and intermixed with other more light-demanding taxa.

Global habitat destruction is bringing species to the edge. Consequently, understanding species dispersal behaviour is becoming essential in order to safeguard vital meta-populations. Nevertheless, dispersal is too often seen as unconditional rather than triggered by habitat cues. We applied radio telemetry on female European stag beetles [Lucanus cervus (L., 1758)] in a mosaic landscape to investigate the hypothesis that dispersal is habitat driven, in this case by canopy closure and presence of suitable dead wood, SDW. We found that the decision to disperse depended on canopy closure and that dispersal distance depended both on SDW availability and canopy closure. Long distance dispersal (by flying), in contrast to small distance dispersal (mainly walking), is shown to be a successful strategy to reach locations with lower canopy closure. We conclude that dispersal of female stag beetles is not unconditional but shaped by habitat resources. It is therefore likely that habitat also affects dispersal of other insects and should be considered in future dispersal studies. For the conservation of the European stag beetle, our results imply that it is essential to provide stepping stones of suitable dead wood, preferably every 100 m and not more than 1 km apart. These stepping stones should be provided in open to half-shaded conditions. Management systems such as coppicing which provide periodic sun-exposure and sufficient amounts of (underground) dead wood are good management procedures for conservation of the stag beetle but they need to be performed at small scales to ensure suitable habitat proximity.

The frequent occurrence of very large trees (diameter at breast height DBH ≥ 80 cm) is a typical element of both primary and secondary old-growth forests. We analyzed the characteristics of very large trees in one of the few stands of lowland old-growth beech forest in Northwestern Europe, regenerated around 1775 and left unmanaged since 1986. We examined their density, diameter range, increment, mortality rate and spatial distribution, based on repeated full dendrometric surveys. In order to evaluate the results, we compared them to original datasets from primary and secondary old-growth beech forests in Europe, and an extensive reference table, compiled from inventories and literature. In our study site, the density of very large trees increased from 31.5 to 34.3 trees ha−1 over the last 25 years, reaching a median DBH of 97 cm (mean 98.9), with the largest tree attaining a DBH of 159 cm. Although the trees were over 240 years old, they still showed an average DBH increment of 4.75 mm year−1 and a low mortality rate (0.89% year−1), indicating that they were still vital. These figures are remarkably high compared to other old-growth beech forest reference sites, where the density of very large trees generally varies between 5 and 20 trees ha−1 (median value 13.1), with a median diameter of 85–90 cm and maximum DBH for beech trees rarely exceeding 100–130 cm. The regular spatial distribution pattern of the very large trees in the studied stand clearly differed from a typical old-growth stand, in which very large trees are randomly distributed. Over the last 25 years though, because of random mortality and ingrowth, the spatial distribution gradually became more random. The extraordinary densities and sizes of the very large trees in our study site can be explained by the favorable climate and site conditions that promote high increments, in combination with the former management interventions of tending and thinning that resulted in continuous non-suppressed growth. Although derived from a very specific case with particular conditions, our observations may be relevant to other beech forests, as they tend to reset certain baseline assumptions for tree size and longevity potential of beech in Northwestern Europe.

The effects of mixing tree species on tree growth and stand production have been abundantly studied, mostly looking at tree species diversity effects while controlling for stand density and structure. Regarding the shift towards managing forests as complex adaptive systems, we also need insight into the effects of structural diversity. Strict forest reserves, left for spontaneous development, offer unique opportunities for studying the effects of diversity in tree species and stand structure. We used data from repeated inventories in ten forest reserves in the Netherlands and northern Belgium to study the growth of pine and oak. We investigated whether the diversity of a tree's local neighbourhood (i.e., species and structural diversity) is important in explaining its basal area growth. For the subcanopy oak trees, we found a negative effect of the tree species richness of the local neighbours, which – in the studied forests – was closely related to the share of shade-casting tree species in the neighbourhood. The growth of the taller oak trees was positively affected by the height diversity of the neighbour trees. Pine tree growth showed no relation with neighbourhood diversity. Tree growth decreased with neighbourhood density for both species (although no significant relationship was found for the small pines). We found no overall diversity-growth relationship in the studied uneven-aged mature forests; the relationship depended on tree species identity and the aspect of diversity considered (species vs. structural diversity).

Tree related Microhabitats (hereafter TreMs) have been widely recognized as important substrates and structures for biodiversity in both commercial and protected forests and are receiving increasing attention in management, conservation and research. How to record TreMs in forest inventories is a question of recent interest since TreMs represent potential indirect indicators for the specialized species that use them as substrates or habitat at least for a part of their life-cycle. However, there is a wide range of differing interpretations as to what exactly constitutes a TreM and what specific features should be surveyed in the field. In an attempt to harmonize future TreM inventories, we propose a definition and a typology of TreM types borne by living and dead standing trees in temperate and Mediterranean forests in Europe. Our aim is to provide users with definitions which make unequivocal TreM determination possible. Our typology is structured around seven basic forms according to morphological characteristics and biodiversity relevance: i) cavities lato sensu, ii) tree injuries and exposed wood, iii) crown deadwood, iv) excrescences, v) fruiting bodies of saproxylic fungi and fungi-like organisms, vi) epiphytic and epixylic structures, and vii) exudates. The typology is then further detailed into 15 groups and 47 types with a hierarchical structure allowing the typology to be used for different purposes. The typology, along with guidelines for standardized recording we propose, is an unprecedented reference tool to make data on TreMs comparable across different regions, forest types and tree species, and should greatly improve the reliability of TreM monitoring. It provides the basis for compiling these data and may help to improve the reliability of reporting and evaluation of the conservation value of forests. Finally, our work emphasizes the need for further research on TreMs to better understand their dynamics and their link with biodiversity in order to more fully integrate TreM monitoring into forest management.

In this pilot study, we examine the relationship between the organisation of property rights and the economic importance of forestry on the one hand and the degree to which integrative nature conservation is formally implemented in forest policy on the other hand. Further, we are interested in whether political institutions moderate this relationship. We first offer a conceptualization of integrative nature conservation in forests and how to measure its implementation in law, ordinances and private agreements for a sample of European national and sub-national jurisdictions (Austria, Croatia, Finland, France, the Netherlands, Switzerland, Flanders, Baden-Württemberg and Piedmont). We subsequently try to assess the implementation of these rules and to relate them both to the structural characteristics of forestry and to an appraisal of pluralism in forest policy. Our qualitative analysis reveals that among the jurisdictions with a more centralized and corporatist forest policy, integrative nature conservation in forests tend to be less formally implemented the more corporatism dominates decision-making. It also confirms the expectation that among the more consensual jurisdictions with a strong forestry sector, rules tend to be less formally implemented. Further, the suspicion prevails that in the latter case, such rules are either complemented with exceptions for private forests or higher compensation. A more in-depth comparative examination is needed to further corroborate these findings. In this pilot study, we examine the relationship between the organisation ofproperty rights and the economic importance of forestry on the one hand and the degree to which integrative nature conservation is formally implemented in forest policy on the other hand. Further, we are interested in whether political institutions moderate this relationship.We first offer a conceptualization of integrative nature conservation in forests and how to measure its implementation in law, ordinances and private agreements for a sample of European national and sub-national jurisdictions (Austria, Croatia, Finland, France, the Netherlands, Switzerland, Flanders, Baden-Wu¨rttemberg and Piedmont). We subsequently try to assess the implementation of these rules and to relate them both to the structural characteristics of forestry and to an appraisal of pluralism in forest policy. Our qualitative analysis reveals that among the jurisdictions with a more centralized and corporatist forest policy, integrative nature conservation in forests tend to be less formally implemented the more corporatism dominates decision-making. It also confirms the expectation that among the more consensual jurisdictions with a strong forestry sector, rules tend to be less formally implemented. Further, the suspicion prevails that in the latter case, such rules are either complemented with exceptions for private forests or higher compensation. A morein-depth comparative examination is needed to further corroborate these findings

International audience; Aim: The tinder fungus Fomes fomentarius is a pivotal wood decomposer in European beech Fagus sylvatica forests. The fungus, however, has regionally declined due to centuries of logging. To unravel biogeographical drivers of arthropod communities associated with this fungus, we investigated how space, climate and habitat amount structure alpha and beta diversity of arthropod communities in fruitbodies of F. fomentarius. Location: Temperate zone of Europe. Taxon: Arthropods. Methods: We reared arthropods from fruitbodies sampled from 61 sites throughout the range of European beech and identified 13 orders taxonomically or by metabarcoding. We estimated the total number of species occurring in fruitbodies of F. fomentarius in European beech forests using the Chao2 estimator and determined the relative importance of space, climate and habitat amount by hierarchical partitioning for alpha diversity and generalized dissimilarity models for beta diversity. A subset of fungi samples was sequenced for identification of the fungus' genetic structure. Results: The total number of arthropod species occurring in fruitbodies of F. fomentarius across European beech forests was estimated to be 600. Alpha diversity increased with increasing fruitbody biomass; it decreased with increasing longitude, temperature and latitude. Beta diversity was mainly composed by turnover. Patterns of beta diversity were only weakly linked to space and the overall explanatory power was low. We could distinguish two genotypes of F. fomentarius, which showed no spatial structuring. Main conclusion: Fomes fomentarius hosts a large number of arthropods in European beech forests. The low biogeographical and climatic structure of the communities suggests that fruitbodies represent a habitat that offers similar conditions across large gradients of climate and space, but are characterized by high local variability in community composition and colonized by species with high dispersal ability. For European beech forests, retention of trees with F. fomentarius and promoting its recolonization where it had declined seems a promising conservation strategy.

For centuries, coppice and coppice-with-standards were the main forest management systems in the northern and central parts of present Belgium. A high population density and a low forest cover in the whole region resulted in a high demand for wood, therefore strict regulations and management regimes were necessary to prevent overexploitation. We illustrate this with a well-documented case, that of Meerdaal Forest in Central Belgium, with reference to other sites in the region. Meerdaal Forest is a woodland 30 km east of Brussels. For centuries its high quality timber stands, especially oak, were managed as coppice-with-standards, with a gradually increasing share of standard trees. Using archive documents and ancient maps, we have reconstructed how this coppice-with-standard management has been developed and optimized over a period of about 500 years. Changes in cutting cycles and configurations were discerned, with a gradual increase of the importance of the standard layer over time. The analysis also showed how wood production could be successfully combined with other sources of income like grazing and pannage. We conclude that former managers of Meerdaal Forest, notwithstanding their lack of scholarship and reference works, developed a state-of-the-art sustainable and flexible management regime that allowed to provide high revenues during many centuries.