Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

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.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... For our study system, we assessed TreM pools and comparatively modeled tree-scale probabilities of different TreMs in relation to tree age, diameter at breast height, and stand-scale factors. Previously, tree cavities have gained most such modelling attention (e.g., Zheng et al. 2015;Puverel et al. 2019;Zlonis et al. 2020), but recent efforts have cleared the way to more systematic treatment of TreMs in forest ecology and management (Vuidot et al. 2011;Winter et al. 2015;Larrieu et al. 2018). Our main question was how variable are the tree-age effects among TreM types and what is their explanatory value. ...
... For each tree, the presence of distinct TreMs was recorded, following the definition and hierarchical typology by Larrieu et al. (2018). Several adjustments regarding TreM types and size criteria were made considering the relevance to biodiversity in our study area, notably to include smallersize TreMs that can be used by invertebrates and fungi in younger stands (Table 1). ...
... An issue addressed was whether the factors affecting the occurrence of smaller TreMs were the same as with those of larger dimensions. To enable such comparison (and also comparison with studies already performed), the original protocol by Larrieu et al. (2018) was recorded in parallel; in the case of informative differences, those results are specifically mentioned below. Circumference of each tree was measured and, for age determination, a trunk core sample at breast height was taken using a 400 mm Haglöf Sweden increment borer. ...
Article
Full-text available
Production forestry is known to reduce the naturally variable microhabitat pools in live trees and their biodiversity by tree removal and broad indirect effects of silviculture. However, the tree-scale processes are not known well enough for microhabitat management for the future. This study investigates how tree age affects the microhabitat occurrence in live trees, its effect modifiers, and explanatory value compared with tree diameter. We inventoried tree-related microhabitats on 879 live aspens (Populus tremula) and Norway spruces (Picea abies) of known age in 141 forests representing contrasting productive site conditions in Estonia. We analysed microhabitat incidence using logistic mixed models for significant tree-scale and stand-scale factors. Most microhabitat types appeared rare even in old trees, and the age effects had various patterns. Only 2% of trees bore five or more microhabitat types. Aspens and spruces had a similar microhabitat diversity before 80 years of age. Stand-level effects varied among microhabitat types but were less significant than tree-level effects; interactions were even rarer. Most effects found could be interpreted through known ecological processes; for example, humidity-dependent epiphytic growth; bark stripping by herbivores; pathogen effects in forests with distinct histories. In contrast, a reliable tree-scale prediction of microhabitat occurrence appears rarely possible; and depending on microhabitat type, either tree age or diameter can be a better predictor. We suggest that managing for tree-related microhabitats in production forests should combine facilitating ecological conditions for microhabitat formation, and early detection and retention of the trees with high microhabitat potential.
... The natural resource of roosting places in old trees is endangered in countries with long-developed forestry, because hollows and cracks reduce the economic quality of wood, and typically, these trees are the first to be removed by forest management [1][2][3]. Natural roosts in trees are of great biocenotic value as they are tree-related microhabitats (TreMs) playing an important role in the forest ecosystem [4][5][6]. ...
... Providing shelter from predation and harsh weather, and serving as places to give birth to offspring, roosts play an essential role in bat reproduction and survival [7][8][9][10][11]. According to classification by [4], forest dwelling bats mostly use two types of TreMs: "woodpecker cavities" and "bark shelters". The availability of potential roosting places (tree hollows, crevices, and dead trees) is one of the factors limiting the occurrence of tree-dwelling bats [1,[12][13][14]. ...
... In a forest-agricultural landscape, the Western barbastelle is able to establish roosts in old wooden buildings (behind protruding facade boards or under shutters) [17][18][19][20]. However, in the forest environment it is a species most commonly found in crevices and roosts under the bark of broadleaved trees ("bark shelters" [4]), which are probably first choice roosting places [21][22][23][24]. For this reason, Western barbastelles are considered as a species that chooses old deciduous forests, which, compared to coniferous stands, usually offer higher frequencies of this type of roosting place [25][26][27]. ...
Article
Full-text available
Białowieża Primeval Forest (BPF, approx. 1700 km 2) is an important forest area in Europe from the point of view of the protection of natural diversity. BPF is covered with old mixed tree stands of mostly natural origin. Norway spruce is a tree species in BPF and covers approx. 27% of its area. Between 2012 and 2017 a large outbreak of the bark beetle Ips typographus (Linnaeus, 1758) took place in the forest, which transformed the stands and left many dead standing trees. At that time salvage logging had begun but was stopped due to protests by scientists and activists and for legal reasons. As a result of research conducted using a radiotelemetry method in 2020, we found that the Western barbastelle bat Barbastella barbastellus (Schreber, 1774) chooses nursery roosts in dead Norway spruce trees, showing ecological plasticity by colonizing a newly available resource. Based on this, we found that the Western barbastelle has a preference for a type of roost rather than a tree species. Insect outbreaks in forests of primary, natural, or semi-natural origin are one of the natural factors that shape the habitat. Removal of dead standing trees disrupts these processes, and in this particular case results in the disappearance of a newly appeared ecological niche.
... A Tree-related Microhabitat (TreM) is defined as "a distinct, welldelineated structure occurring on living or standing dead trees, that constitutes a particular and essential substrate or life site for species or species communities during at least a part of their life cycle to develop, feed, shelter or breed" . TreMs support a wide array of biodiversity (see Table 2 in Larrieu et al., 2018) that is not usually supported by other forest structures, such as deadwood items (Stokland et al., 2012). Several studies have highlighted the significant impact of an increase in TreM-bearing tree (hereafter called habitat-tree) density on species richness for several taxa (see e.g. ...
... Bouget et al., 2013,b, Larrieu et al., 2019, and Winter and Möller, 2008 for saproxylic beetles; Regnery et al., 2013a;Paillet et al., 2018 for bats and birds; Larrieu et al., 2019 for polypores and hoverflies; Basile et al., 2020 for insects and bats). Hence, some authors have suggested using TreMs as indirect biodiversity indicators in forest ecosystems and as tools to promote integrative forest management (Kraus and Krumm, 2013;Winter and Möller, 2008, Regnery et al., 2013bBütler et al., 2013;Larrieu et al., 2018;Asbeck et al., 2021). However, at plot and stand scales, the relationship between TreM density and/or diversity with variations in biodiversity are not so straightforward. ...
... From the literature and based on the authors' expertise, each feature was evaluated in terms of its potential effect on TreM formation: 'highly probable effect' was assigned if at least one study indicated a strong and explicit effect of that factor on TreM formation, or 'probable effect' if at least one reference reported a probable or indirect effect and the authors' expertise confirmed that this may indeed be the case. We here considered the 15 TreM groups described by Larrieu et al. (2018) as the best compromise between precision and simplicity for analysis (Table 2SM). ...
Article
Tree-related microhabitats (TreMs) have been identified as key features for forest-dwelling taxa and are often employed as measures for biodiversity conservation in integrative forest management. However, managing forests to ensure an uninterrupted resource supply for TreM-dwelling taxa is challenging since TreMs are structures with a limited availability, some of which are triggered by stochastic events or require a long time to develop. At the tree scale, the role of tree species, diameter at breast height (dbh) and status (i.e. living vs standing dead) for favouring TreM occurrence has been quantified and modelled in several studies, since these tree features are routinely recorded in the field. However, TreM occurrence remains difficult to predict, hampering the elaboration of applicable management strategies that consider TreMs. Using an international database encompassing 110,000 trees, we quantified the explanatory power of tree species, dbh, status, time since last harvest and plot context for predicting TreM occurrence at the tree level. Plot context is so far a “black box” that combines local environmental conditions, past and current management legacies, with local biotic features that have high explanatory power for predicting TreM occurrence. Then, based on the literature, we established a set of 21 factors related to site, stand and tree features for which there is a strong assumption that they play a key role in TreM formation. Finally, we identified a sub-set of nine features that should be recorded in the future to provide additional information to enable better prediction of the occurrence of particular TreMs: (i) at plot level: slope, exposure, altitude and presence of cliffs; and (ii) at tree level: bark features, phyllotaxis and compartmentalization capacity of the tree species, plus ontogenic stage and physiological state of the individual tree sampled.
... Data collection refers mainly to tree characteristics, such as tree species, dendrometric measurements [tree height, crown size, DBH (diameter at 1.3 m height) among others], and tree-related microhabitats. The plot and tree-level data were collected per the suggestion from i-tree-Eco (i-Tree-eco, 2021), whereas microhabitat data collection was done per the guidelines of Larrieu et al. (2018). In addition, the microhabitat data was collected for trees with a minimum DBH of 20 cm as smaller trees rarely bare microhabitats (Grossmann et al., 2020). ...
... Forty-seven different tree microhabitat types were surveyed following the guidelines in the Larrieu et al. (2018). The count of each tree microhabitat type found in a single tree represents the microhabitat richness of that tree. ...
... In urban trees, pruning is used to maintain mechanical and biological stability (Paganová & Vyhnáliková, 2018). These practices also help reduce the risk of accidents caused by e.g., broken, or dead branches, which are considered tree microhabitats (Larrieu et al., 2018). Moderate tree maintenance leads to lower tree microhabitats on urban trees (Grossmann et al., 2020). ...
Article
Reducing trade-offs among ecosystem services (ES) from urban and peri-urban forests (UPF) is crucial for human wellbeing. We performed spatial analyses and quantified the supply and trade-offs between 23 ES (grouped into three categories: provisioning, regulating, and supporting) from UPF in the Karlsruhe region, southwest Germany. The supply of ES was calculated, normalized, and mapped from field data collected at 201 randomly selected plots in UPF, located in agricultural land, built-up areas (i.e., artificial surfaces), and forest and seminatural areas. Trade-offs were calculated as the root mean squared error between the benefits from two categories of ES. Predominantly, there was a synergy between provisioning and regulating ES; however, trade-offs with supporting ecosystem services were detected in all three land-uses. The UPF areas with a high supply of supporting ES (e.g. tree species, structural and tree microhabitat diversity) had a lower supply of regulating and provisioning ES, resulting in trade-offs. This study demonstrates trade-off patterns between the ES in UPF, which should be considered in the management of UPF and sustainable city design. Current UPF should be transformed to a more multifunctional and climate-resilient state to guarantee ES and human wellbeing in cities.
... They act as carbon storage and sinks (Achard & Hansen, 2012;Frey et al., 2016;Luyssaert et al., 2008). They have a role in the protection of water resources and the prevention of soil erosion (Brockerhoff et al., 2017;Watson et al., 2018) and also host a myriad of features with high conservation value promoting biodiversity (Bauhus et al., 2009;Burrascano et al., 2013;Larrieu et al., 2018;Paillet et al., 2010Paillet et al., , 2015Paillet et al., , 2017. Wirth et al. (2009) present various ways to define forest maturity. ...
... The use of the time since the last harvesting is a way of assessing the degree of naturalness of the forest in question, with increased occurrence of maturity feature or structural attributes in older unmanaged plots. Those plots display more trees with larger diameters at breast height (Burrascano et al., 2013;Heiri et al., 2009;Paillet et al., 2015), a higher abundance of tree-related microhabitats (Larrieu et al., 2018;Paillet et al., 2017;Winter & Möller, 2008) along with high volumes of deadwood (Harmon, 2009;Siitonen et al., 2000). Those specific structural attributes harboured by more mature forests also have high conservation value for biodiversity (Bauhus et al., 2009;Burrascano et al., 2013;Siitonen et al., 2000). ...
... In this study, we used inventories of forest stand structure issued from forest reserves and managed forests to calibrate a generalised linear mixed model explaining the time since the last harvesting with selected attributes of maturity, herein called structural variables, combined with environmental variables. We hypothesised that time since the last harvesting would be positively influenced by a high volume of large logs and snags (Heiri et al., 2009;Portier et al., 2020;Siitonen et al., 2000) and high basal area of very large trees (Burrascano et al., 2013;Paillet et al., 2015), high diversity of tree-related microhabitats (Larrieu et al., 2018;Paillet et al., 2017;Winter & Möller, 2008) and decay stages (Siitonen et al., 2000;Winter & Möller, 2008;Wirth et al., 2009). We expected time since last harvesting to be negatively correlated with the volume of stumps (Paillet et al., 2015;Siitonen et al., 2000) and stem density of medium trees (Paillet et al., 2015). ...
Article
Full-text available
Aim The distribution of overmature forests in metropolitan France is poorly known, with only a few well-studied prominent sites, and has never been evaluated countrywide. Here, we modelled French forest reserves' time since the last harvesting operation—a proxy for forest maturity—then inferred the current statistical distribution of overmature forests (i.e., forests over 50 years without harvesting) in France. Location Metropolitan France. Methods We used inventories from forest reserves and managed forests to calibrate a generalised linear mixed model explaining the time since the last harvesting with selected structural attributes and environmental variables. We then projected this model on the independent National Forest Inventory dataset. We thus obtained an updated estimation of the proportion and a rough distribution of overmature forest stands in metropolitan France. Results We found that high basal area of very large trees, high volumes of standing and downed deadwood, high diversity of tree-related microhabitats and more marginally diversity of decay stages best characterised the time since the last harvesting. Volumes of stumps and high density of coppices translating legacy of past forest management also distinguished more overmature plots. Our projection yielded an estimated 3% of French forests over 50 years without harvesting mostly located in more inaccessible areas (i.e., mountainous areas). Main conclusions Our study showed that the time since the last harvesting could be derived from a combination of key structural attributes characterising overmature temperate forests. It gives the first robust statistical estimate of the proportion of overmature forests in France and may serve to report on their status. Our method could be extended in countries with accessible National Forest Inventory and calibration data, thus producing indicators at an international level.
... The decision whether to harvest or retain individual trees presents multiple trade-offs between for example, economics, biodiversity, and carbon balance and represents a complex decision with multidimensional problems in time and space. The need to train practitioners and students to evaluate these trade-offs and to explore integrated forest 55 management has promoted the development of marteloscopes by the Integrate+ project at the European Forest Institute (EFI) (Cosyns et al., 2018;Kraus et al., 2018;Joa et al., 2020). Marteloscopes are in general one-hectare large, rectangular forest sites where all trees are numbered, mapped, and recorded for field-based presentation of spatially explicit problems including forest growth, economics, and biodiversity. ...
... Based on expert assessment in the field, each stem was visually sectioned into quality grades (A, B and C quality stem wood, industry wood (D), and fuelwood (F)). The stem section volumes were calculated using mid-section diameters derived from a tapering factor as described in (Kraus et al., 2018). The stem section volumes of A, B, C, and D 100 quality were summed together and subtracted from the total tree volume. ...
... A survey of tree TreMs was the basis for deriving an ecological value for each tree with various saproxylic and epixylic microhabitat types (Kraus et al., 2016;Larrieu et al., 2018). The ecological value of each tree, with units denoted as 'habitat points', is based on 115 the number of TreMs, their respective rarity gradient, and the time span needed for the TreM to develop (Kraus et al., 2018). ...
... Habitat trees (also called veteran trees) are large and old trees that provide microhabitats ( Figure 6). Microhabitats in the forms of hollows, crevices, cracks, decaying residues and so forth are key elements for biodiversity conservation in forests (Bütler et al. 2013;Larrieu and Cabanettes 2012;Larrieu et al. 2018). Similar to deadwood, knowledge about habitat trees and microhabitats and their importance for biodiversity has increased significantly (Fritz and Heilmann-Clausen 2010, Gossner et al. 2016, Asbeck et al. 2021, Courbaud et al. 2022). ...
... Cavity-bearing habitat trees ( Figure 6) are among the most important habitats for specialized forest wildlife, including forest bats and birds while several highly threatened forest beetles also depend on old cavities with organic matter. Such trees are a typical element of old-growth forests, although the density of large habitat trees is often less than one per hectare in managed forests Lachat 2009, Larrieu andCabanettes 2012;Larrieu et al. 2018). However, in managed forests and cultural landscapes, they are still routinely cut for safety reasons or economic return. ...
... The latter have not shared a co-evolutionary path with other non-tree species native to Europe and are therefore less likely to provide these species with suitable habitats (Felton et al. 2013, Gossner et al. 2009). While tree species choice will influence canopy closure and light transmission for the understorey vegetation or the diversity of tree-related microhabitats (Larrieu et al. 2018), it also affects leaf litter composition (nutrient rich litter versus nutrient poor litter, Desie et al. 2020a) and, in turn, the interplay between soil decomposer communities, the humus type and soil acidity (Desie et al. 2020b). In this context, conversion from ancient broadleaved forests to exotic conifer stands leads to strong, largely irreversible changes in their belowground communities and herb layer (Desie et al. 2019). ...
Article
Full-text available
Aim of the report - This report aims to explore the importance of biodiversity in the context of European forests and to make suggestions on how this biodiversity can be effectively maintained and enhanced through protection, management and restoration. The term Europe in this document means European Union, except where mentioned otherwise. The report is meant for all kinds of decision-makers at the EU, national and local levels who are confronted with policy and management decisions related to biodiversity conservation and sustainable forest management. Although the primary focus is on the EU, most of the insights and recommendations made should be transferrable, with varying degrees of customisation where necessary, to non-EU countries as well. This report does not and cannot provide black and white guidelines on how to support forest biodiversity, rather it is designed to be a reference source for information and inspiration on the basics of forest biodiversity and forest biodiversity management. As such, it is a useful tool that highlights what is possible for evidence-based decision-making on this complex and dynamic matter. The report is purposely written and presented in a manner to stimulate dialogue on maintaining and restoring forest biodiversity while illuminating ways to bridge gaps between divergent viewpoints on the available options to avoid the loss of the irreplaceable and invaluable natural and cultural heritage inherent to European forest biodiversity.
... Tree-related microhabitats (TreMs) can fulfill the roles of biodiversity and naturalness indicators. They are defined as "all distinct and welldelineated structures occurring on living or standing dead trees, that constitute a particular and essential substrate or life site for species or species communities during at least a part of their life cycle to develop, feed, shelter or breed" (Larrieu et al., 2018b). They can be regrouped in seven main forms, based on morphological characteristics, and use by the associated taxa: (i) cavities, (ii) tree injuries and exposed wood, (iii) crown deadwood, (iv) excrescences, (v) fruiting bodies of saproxylic fungi and fungilike organisms, (vi) epiphytic, epixylic, and parasitic structures (e.g., nest), and (vii) exudates (Figure 1; Larrieu et al., 2018b). ...
... They are defined as "all distinct and welldelineated structures occurring on living or standing dead trees, that constitute a particular and essential substrate or life site for species or species communities during at least a part of their life cycle to develop, feed, shelter or breed" (Larrieu et al., 2018b). They can be regrouped in seven main forms, based on morphological characteristics, and use by the associated taxa: (i) cavities, (ii) tree injuries and exposed wood, (iii) crown deadwood, (iv) excrescences, (v) fruiting bodies of saproxylic fungi and fungilike organisms, (vi) epiphytic, epixylic, and parasitic structures (e.g., nest), and (vii) exudates (Figure 1; Larrieu et al., 2018b). They thus represent a wide variety of structures, necessary for many animal, vegetal or fungal species, and several species are highly-dependant on specific TreMs. ...
... Forest management and biodiversity conservation both benefit from exchanges among researchers and practitioners, and more generally from the transferability of concepts and the assessment of their robustness in different contexts. A quick look at the literature on TreMs suggests, however, that the concept has developed mainly in Europe, and particularly in the temperate and Mediterranean regions of that continent (Kraus et al., 2016;Larrieu et al., 2018b). Trees and forests in this area demonstrate certain characteristics (e.g., tree size, TreM development dynamics, history of anthropogenic disturbance) that may differ from other territories and current knowledge on TreMs may not be directly applicable outside the regions where they are currently studied. ...
Article
Full-text available
Sustainable management of forest ecosystems requires the use of reliable and easy to implement biodiversity and naturalness indicators. Tree-related microhabitats (TreMs) can fulfill these roles as they harbor specialized species that directly or indirectly depend on them, and are generally more abundant and diverse in natural forests or forests unmanaged for several decades. The TreM concept is however still recent, implying the existence of many knowledge gaps that can challenge its robustness and applicability. To evaluate the current state of knowledge on TreMs, we conducted a systematic review followed by a bibliometric analysis of the literature identified. A total of 101 articles constituted the final corpus. Most of the articles (60.3%) were published in 2017 or after. TreM research presented a marked lack of geographical representativity, as the vast majority (68.3%) of the articles studied French, German or Italian forests. The main themes addressed by the literature were the value of TreMs as biodiversity indicators, the impact of forest management on TreMs and the factors at the tree- and stand-scales favoring TreMs occurrence. Old-growth and unmanaged forests played a key role as a “natural” forest reference for these previous themes, as TreMs were often much more abundant and diverse compared to managed forests. Arthropods were the main phylum studied for the theme of TreMs as biodiversity indicators. Other more diverse themes were identified, such as restoration, remote sensing, climate change and economy and there was a lack of research related to the social sciences. Overall, current research on TreMs has focused on assessing its robustness as an indicator of biodiversity and naturalness at the stand scale. The important geographical gap identified underscores the importance of expanding the use of the TreMs in other forest ecosystems of the world. The notable efforts made in recent years to standardize TreM studies are an important step in this direction. The novelty of the TreM concept can partially explain the thematic knowledge gaps. Our results nevertheless stress the high potential of TreMs for multidisciplinary research, and we discuss the benefits of expanding the use of TreMs on a larger spatial scale.
... The amount of dead wood has a strongly affects species diversity. (Larrieu et al., 2018;Karpiński et al., 2021). SDW Volume (m 3 ) of standing dead wood (≥7 cm in perimeter) per hectare. ...
... SDW Volume (m 3 ) of standing dead wood (≥7 cm in perimeter) per hectare. Dead wood position affects saproxylic community (Larrieu et al., 2018) Tree Microhabitats ...
... Excrescences Burr and cankers, mainly caused by reactive growth to parasitic or microbial intrusion, where tree create specific structures to isolate the pathogen.It is measured as the number of trees with trunk excrescences (with a diameter of ≥ 10 cm) per hectare. This microhabitat hosts a diverse community (Winter and Möller, 2008;Kraus et al., 2016;Larrieu et al., 2018;Ramilo et al., 2017) Hollows Measured as the number of trees with tree hollows (≥10 cm in diameter) per hectare. This microhabitat is a keystone for saproxylic beetles (Müller et al., 2013;Micó et al., 2020) CerGalleries Number of trees with visible damage caused by Cerambyx beetles per hectare. ...
Article
Full-text available
Forests of the Mediterranean Basin provide a wide range of provisioning and regulating services that are currently jeopardised by land-use change. Although many ecosystem services are mediated by insects, most of the studies that have focused on how to enhance diversity in traditionally managed forests are about plants and vertebrates. Quercus pyrenaica woodlands of the Western Iberian Peninsula constitute a scenario in which traditional human practices (i.e., extensive livestock grazing, pollarding, firewood, forest thinning, etc.), and their progressive abandonment, have generated differences in landscape that affect habitat and microhabitat structures. We used saproxylic beetles (deadwood-dependent species) as biological indicators because they are the most diverse taxa and provide important ecosystem services related to deadwood decomposition, forest pest control and pollination. We modelled the response of two taxonomic (species richness and abundance), one ecological (species diversity of order 1) and two functional (functional richness and redundancy) diversity metrics to the environmental variables that result from traditional management or its abandonment at habitat and microhabitat levels. We included 16 explanatory variables related to forest structure, tree microhabitats and abiotic factors, which were grouped into eight principal components. Linear regression was the best fitting model for data. The resulting models were used to perform diversity predictions in different scenarios. We found that abandonment of some traditional forest management activities in the Mediterranean Region reduced taxonomic saproxylic beetle diversity, which may be further aggravated by climate change. We suggest minimal management actions to improve taxonomic and ecological saproxylic beetle diversity related to habitat and tree management (i.e., maintenance of >20% scrub coverage, >20 m³/ha of deadwood on soil and >20 hollow trees/ha). However, actions that boost saproxylic biodiversity do not ensure the community’s higher functional resilience. We should also promote tree microhabitat diversity to reduce the vulnerability of saproxylic beetle functions to environmental changes.
... Small structures on living or dead trees, which are distinct and diverse habitats are summarized under the term tree-related microhabitat or 'TreM' in short (Bauhus et al., 2009;Vuidot et al., 2011;Winter, 2008). Examples of TreMs are woodpecker cavities, branch-or stembreakage, fungal fruiting bodies, injuries or epiphytes (Rita Bütler et al., 2020;Kraus et al., 2016;Larrieu et al., 2018). The ecological relevance of TreMs has been increasingly studied over the last years (Table 1) (Asbeck et al., 2019;Kõrkjas et al., 2021;Kozák et al., 2018;Larrieu et al., 2016;Paillet et al., 2019;Winter et al., 2014;Winter and Möller, 2008). ...
... In total more than 54000 living trees from forests all across Europe have been analyzed in this study ( Figure 1). All trees were inventories summarized for TreMs based on a detailed methodology and typology proposed by Larrieu et al. (2018) and Kraus et al. (2016). TreMs include, for instance, woodpecker cavities, trunk and mould cavities, stem injuries and wounds, crown deadwood, cankers and burrs (Appendix Table 4). ...
... which are too small to be considered as a TreM in the meaning of the TreM catalog, as defined by Larrieu et al. (2018), are able to function as habitat as well. Thus we suggest to refer to the term 'habitat tree' in the context of retention forestry as trees bearing a significant number of different TreMs (Figure 4, 5). ...
Thesis
Habitat trees – one of the key elements of integrative retention approaches in European forests – are increasingly studied regarding their benefits to forest biodiversity. In this regard, treerelated microhabitats (TreMs) and deadwood serve as indicators of forest biodiversity. Specific recommendations of amounts of deadwood to be retained in managed forest stands to support related taxa are available, but not for TreMs. Retention of habitat trees aims to increase availability of TreMs in managed forests. To be able to refine selection criteria for habitat trees, I focused in this thesis on factors affecting TreMs on living trees. Therefore, I calculated species specific diameter thresholds bases on TreM occurrences, I investigated the effect of tree maintenance on TreMs in urban areas and I evaluated the short-term value of the retention of habitat tree groups. Chapter 1. The aim of this chapter was to explain TreM occurrence from a qualitative perspective by considering their diversity. Tree diameter at breast height (dbh), tree species, and canopy class were useful predictors of TreM diversity. TreM diversity on broad-leaved trees was on average higher than in conifers of the same diameter. In contrast to TreM abundance their diversity saturated towards higher dbh levels. Those TreM saturation levels were used to derive diameter thresholds. Habitat trees support not only more, but also more diverse, microhabitats in comparison to crop trees. Chapter 2. In this chapter I further developed the findings of chapter one and focused on the calculation of species specific diameter thresholds to precise recommendations for selecting habitat trees. Based on the relation between TreMs and tree diameter as well as TreMs and species I derived diameter thresholds for 18 European tree species (13 broad-leaved, 5 coniferous). Those thresholds refer to statistically disproportionate high levels of TreM richness or abundance. Complementing other aspects that need to be considered during habitat tree selection processes in managed forest stands, I recommend to select habitat trees with or close to a dbh of 70 cm for broadleaves and 86 cm for conifers. The differences of dbh thresholds between broadleaves and conifers as well as between species indicate species specific TreM dynamic. Chapter 3. In the third chapter, I investigated the TreM availability on urban trees along a maintenance gradient in Montréal, Canada. Intensive tree maintenance in urban trees led to levels of certain microhabitats such as cavities and injuries that were comparable to natural, unmanaged forests. Light maintenance of urban trees encouraged more crown deadwood than typical and intensive maintenance levels. My results underline the importance of conserving and maintaining large living trees, especially in urban areas to provide tree microhabitats. These results also demonstrate the important role of intensive tree maintenance in stimulating tree microhabitat development in urban areas. Chapter 4. Here, I addressed the effectiveness of habitat tree group (HTG) retention in forests of Baden-Württemberg, Germany, 10 years after the introduction of the approach. Large living trees (LLTs), standing deadwood and TreMs were significantly more abundant in HTGs than in reference plots. When retaining 5 % of a forest stand area as HTG, old-growth attributes increased significantly at the stand scale: amount of LLTs doubled and its volume almost tripled, and standing deadwood increased on average by 25 %. However, quantities of both attributes remain below recommended minimum thresholds. Retaining 5 % of stand area in HTG had a significantly positive effect on woodpecker cavities, rot holes and exposed heartwood, whereas 15 to 25 % area in HTGs would be required to increase stand level abundance of concavities, exposed sapwood or crown deadwood significantly. Retention of HTGs enriched managed, multiple-use forests with old growth structural attributes. Yet, the selection of HTGs could be made more efficient by focusing on forest patches with high tree volume or low tree density and by further considering snags, tree species mixture and LLTs as well as less vital trees. Overall the findings of this thesis suggest, that common tree attributes (species, diameter, vitality, canopy class, life status) can be used to predict the occurrence of TreMs. Species specific diameter thresholds can help to identify trees with higher levels of TreM richness. The specification of tree attributes in regard to TreMs allow to optimize habitat tree selection procedures. In addition or absence of trees rich in TreMs, tree maintenance could increase structural diversity. Intensively maintained trees providing comparable amounts of TreMs to trees from long-term unmanaged forests emphasize the relevance of artificially induced structures. To consider a holistic view on trees as biodiversity relevant feature throughout the landscape, I propose to expand further TreM research to urban and rural trees. Regardless how TreMs evolved and in which landscape they occur, the relation between TreMs and related taxa needs to be specified to strengthen the biodiversity indicating function of TreMs. Results from current TreM inventories, that followed standardized procedures, allow a approximation of TreM occurrence on a landscape level by linking species and diameter information to observed TreM abundances. To better understand development and persistence of TreMs repeated inventories were needed. Finally, my results allow to refine selection criteria of habitat trees based on the presence of TreMs and the consideration of species specific diameter thresholds. Furthermore, in absence of TreMs or when minimum diameters were not reached, I propose the possibility of artificial TreM creation to be useful for structural enrichment.
... The complex three-dimensional structure of tree crowns also provides ecological space of reduced predation for arthropods, known as an escape or enemy-free space (Lawton, 1983;Wardhaugh, 2014). In addition, the canopy provides a unique set of microhabitats and resources, with specific tree-related microhabitats such as mistletoe, suspended soils, epiphytes, perched dead branches, upper trunk cavities, and fruiting bodies of opportunistic fungi (Ulyshen, 2011;Larrieu et al., 2018), allowing the differentiation of dedicated habitat and/or trophic guilds of arthropods. Ultimately, this results in the establishment of complex food webs (Nakamura et al., 2017). ...
... They promote tree-related microhabitats associated with reduced tree vigor or decaying trees (e.g., cavities initiated by break-offs of scaffold dead branches, perched dead branches and ascending dead branches emerging from the canopy, stress-induced broomlike mass of twigs, fruiting bodies of opportunistic fungi. . .) (Figures 1, 2; Ojeda et al., 2007;Larrieu et al., 2018;Cours et al., 2021). Consequently, because forest declines and diebacks promote the accumulation of such biological legacies , they contribute to increase the structural complexity at multiple scales. ...
... We used our RF classification model with the PBIA approach to identify the dead crown pixels over large areas around our study plots. Our approach did not allow us to assess dead-tree density so we estimated the cumulative surface area of the dead and dying tree parts, i.e. the dead crowns (Larrieu et al. 2018). We then mapped and summed the dead crown pixels to assess a level of forest dieback over several spatial scales. ...
... In addition, we observed a significant landscape effect of forest dieback on the abundance of both cavicolous and fungicolous species (Fig. 4e). This result suggest that forest dieback does not just increase deadwood amount and canopy openness but also favours the development of tree-related microhabitats such as the fruiting bodies of saproxylic fungi and cavities (e.g., rot-holes; Ojeda et al. 2007;Larrieu et al. 2018;Speckens 2021). ...
Article
Full-text available
Context Many forest ecosystems around the world are facing increasing drought-induced dieback, causing mortality patches across the landscape at multiple scales. This increases the supply of biological legacies and differentially affects forest insect communities. Objectives We analysed the relative effects of local- and landscape-level dieback on local saproxylic beetle assemblages. We assessed how classical concepts in spatial ecology (e.g., habitat-amount and habitat-patch hypotheses) are involved in relationships between multi-scale spatial patterns of available resources and local communities. Methods We sampled saproxylic beetle assemblages in commercial fir forests in the French highlands. Through automatic aerial mapping, we used percentage of dead tree crown pixels to assess dieback levels at several nested spatial scales. We analysed beetle taxonomic, phylogenetic and functional diversity related to differing levels of multi-scale dieback. Results We found that taxonomic, functional, and phylogenetic diversity of saproxylic beetle assemblages significantly benefitted from forest dieback, at both local and landscape scales. We detected significant effects in the multiplicative models combining local and landscape variables only for phylogenetic diversity. Increased landscape-scale dieback also caused a functional specialisation of beetle assemblages, favouring those related to large and well-decayed deadwood. Conclusions Increasing tree mortality under benign neglect provides conservation benefits by heterogenising the forest landscape and enhancing deadwood habitats. Legacy retention practices could take advantage of unharvested, declining forest stands to promote species richness and functional diversity within conventionally managed forest landscapes.
... In this way, we could account for possible associations among species (as for research question 1), and for those species directly relying on structures which are influenced by forest management (as for research question 2). We modeled the abundance responses to the environment of co-occurring and potentially associated birds of the cavity-nesting and canopy-foraging guilds, accounting for habitat structure, management intensity, availability of tree-related microhabitats (TreMs) [57], and landscape composition. We expected that the response of each species to the habitat structure in presence of associated species would deviate from the responses excluding association among species. ...
... The abundance and richness of TreMs was retrieved from previous research in the same plots [94]. TreMs are considered to be "a distinct, well delineated structure occurring on living or standing dead trees, that constitutes a particular and essential substrate or life site for species or species communities during at least a part of their life cycle to develop, feed on, using as shelter or to breed" [57] and have shown correlations to the richness and abundance of forest-dwelling vertebrates and (saproxylic) insects [5,6,97]. TreMs are usually grouped into seven forms, including cavities, tree injuries and exposed wood, crown deadwood, excrescences, fruiting bodies of saproxylic fungi and slime molds, epiphytic, epixylic and parasitic structures, and fresh exudates such as sap run and heavy resinosis [98]. ...
Article
Full-text available
Background Species co-occurrences can have profound effects on the habitat use of species, and therefore habitat structure alone cannot fully explain observed abundances. To account for this aspect of community organization, we developed multi-species abundance models, incorporating the local effect of co-occurring and potentially associated species, alongside with environmental predictors, linked mainly to forest management intensity. We coupled it with a landscape-scale analysis to further examine the role of management intensity in modifying the habitat preferences in connection with the landscape context. Using empirical data from the Black Forest in southern Germany, we focused on the forest bird assemblage and in particular on the cavity-nesting and canopy-foraging guilds. We included in the analysis species that co-occur and for which evidence suggests association is likely. Results Our findings show that the local effect of species associations can mitigate the effects of management intensity on forest birds. We also found that bird species express wider habitat preferences in forests under higher management intensity, depending on the landscape context. Conclusions We suspect that species associations may facilitate the utilization of a broader range of environmental conditions under intensive forest management, which benefits some species over others. Networks of associations may be a relevant factor in the effectiveness of conservation-oriented forest management.
... The complex three-dimensional structure of tree crowns also provides ecological space of reduced predation for arthropods, known as an escape or enemy-free space (Lawton, 1983;Wardhaugh, 2014). In addition, the canopy provides a unique set of microhabitats and resources, with specific tree-related microhabitats such as mistletoe, suspended soils, epiphytes, perched dead branches, upper trunk cavities, and fruiting bodies of opportunistic fungi (Ulyshen, 2011;Larrieu et al., 2018), allowing the differentiation of dedicated habitat and/or trophic guilds of arthropods. Ultimately, this results in the establishment of complex food webs (Nakamura et al., 2017). ...
... They promote tree-related microhabitats associated with reduced tree vigor or decaying trees (e.g., cavities initiated by break-offs of scaffold dead branches, perched dead branches and ascending dead branches emerging from the canopy, stress-induced broomlike mass of twigs, fruiting bodies of opportunistic fungi. . .) (Figures 1, 2; Ojeda et al., 2007;Larrieu et al., 2018;Cours et al., 2021). Consequently, because forest declines and diebacks promote the accumulation of such biological legacies , they contribute to increase the structural complexity at multiple scales. ...
Article
Full-text available
Global change challenges the adaptive potential of forests. Large-scale alterations of forest canopies have been reported across Europe, and further modifications are expected in response to the predicted changes in drought and windstorm regimes. Since forest canopies are dynamic interfaces between atmosphere and land surface, communities of canopy-dwelling insects are at the forefront of major changes in response to both direct and indirect effects of climate change. First, we briefly introduce the factors shaping arthropod communities in the canopy of temperate forests. Second, we cover the significant impacts of a forest decline on canopy structure and functioning, and more specifically its contrasted effects on insect microhabitats, trophic resources and forest microclimates. Deleterious effects may be expected for several guilds of leaf-dwelling insects. Nonetheless, a forest decline could also lead to transient or long-lasting resource pulses for other canopy-dwelling guilds, especially saproxylic species depending on deadwood substrates and tree-related microhabitats. The novel microclimates may also become more favorable for some particular groups of insects. We pinpoint current knowledge gaps and the technological locks that should be undone to improve our understanding of the canopy biotope and biodiversity in temperate forests. We highlight the need for integrative approaches to reveal the mechanisms at play. We call for cross-scale studies and long-term collaborative research efforts, involving different disciplines such as community and disturbance ecology, plant and insect ecophysiology, and thermal ecology, to better anticipate ongoing functional and conservation issues in temperate forest ecosystems.
... We surveyed tree-related microhabitats (TreMs) at each tree following the typology of Larrieu et al. (2018). We only considered TreMs that could potentially enhance bat prey abundance and/or provide suitable summer roosts for bats based on expert knowledge and existing literature (Regnery et al., 2013;Larrieu et al., 2018). ...
... We surveyed tree-related microhabitats (TreMs) at each tree following the typology of Larrieu et al. (2018). We only considered TreMs that could potentially enhance bat prey abundance and/or provide suitable summer roosts for bats based on expert knowledge and existing literature (Regnery et al., 2013;Larrieu et al., 2018). Thus, we inventoried the presence/absence of 12 TreM types (Appendix S1). ...
Article
Isolated trees are increasingly recognised as playing a vital role in supporting biodiversity in agricultural landscapes, yet their occurrence has declined substantially in recent decades. Most bats in Europe are tree-dependent species that rely on woody elements in order to persist in farmlands. However, isolated trees are rarely considered in conservation programs and landscape planning. Further investigations are therefore urgently required to identify which trees – based on both their intrinsic characteristics and their location in the landscape – are particularly important for bats. We acoustically surveyed 57 isolated trees for bats to determine the relative and interactive effects of size, tree-related microhabitat (TreM) diversity and surrounding landscape context on bat activity. Tall trees with large diameter at breast height and crown area positively influenced the activity of Pipistrellus pipistrellus and small Myotis bats (Myotis spp.) while smaller and thinner trees favoured M. myotis activity. The diversity of TreMs that can be used as roosts had a positive effect on (i) Barbastella barbastellus activity only when trees were relatively close (<50 m) to woody patches, (ii) Pipistrellus nathusii/kuhlii activity only in the most heterogeneous landscapes, and (iii) Myotis spp. activity only in the most forested environment (>10% within 100 radius scale). The potential benefits of isolated trees for bats result from ecological mechanisms operating at both tree and landscape scales, underlining the crucial need for implementing a multi-scale approach in conservation programs. Maintaining the largest and most TreM-diversified trees located in the most heterogeneous agricultural landscapes will provide the greatest benefits.
... The retention of old-growth forest attributes has therefore become a major strategy to help integrate biodiversity conservation into forest management (Fedrowitz et al., 2014;Gustafsson et al., 2012;Lindenmayer et al., 2012). After having focused on dead wood Müller & Bütler, 2010), conservationists have now realized that a large range of structures grouped under the term 'tree-related microhabitats', and present both on dead and living trees, are also of key importance for biodiversity Larrieu, Paillet, et al., 2018). ...
... For this study, we defined 11 TreM groups based on morphology and their role in biodiversity (see Appendix S2): woodpecker breeding hole, rothole, dendrotelm, root concavity, bark loss, exposed heartwood, crack, crown deadwood, burl or canker, polypore, sap run. These groups are quite close to the 15 TreM groups proposed in Larrieu, Paillet, et al. (2018). Our 11 groups often combine several types described in the most detailed field protocols in the global dataset: ...
Article
The retention of trees bearing tree‐related microhabitats (TreMs) has become an important means of conserving biodiversity in production forests. However, we lack estimates of TreM formation rates and evidence on factors driving TreM formation. Based on the observation of 80,099 living trees from 19 species groups in Europe and Iran, we estimated the probability of TreM occurrence on trees and the associated rate of first TreM formation as a function of tree DBH, management, tree species group and random site effects. We built a separate model for each of 11 TreM groups. The hazard rate of first TreM formation (defined as the probability of formation of a first TreM forming on a tree that is known to have none, during an infinitesimal DBH increment) increased with DBH for some TreM groups like breeding‐woodpecker‐hole, rot‐hole or root‐concavity, indicating an acceleration in TreM formation during tree growth. However, it decreased with DBH for TreM groups like bark‐loss or dendrotelm, indicating slower formation on very large trees. Most TreM groups had reduced formation rates in managed forests (last logging less than 100 years ago) compared to unmanaged forests (no logging for at least 100 years), with the exception of dendrotelms. No general difference appeared between broadleaves and conifers but early‐successional species tended to have different TreMs than mid‐ and late‐successional species. Abies, Alnus, Betula, Fagus, Prunus, Quercus, Sorbus, Tilia and Ulmus displayed high formation rates for six TreM groups or more. Variability among sites was considerable. Synthesis and applications: The rate of formation of tree related microhabitats (TreMs) varies greatly among TreM groups, tree species, locations, tree diameters at breast height and forest management. The high rate of formation of some TeM groups on small trees implies that tree retention for biodiversity should concern trees of all sizes and start as soon as thinning operations have occurred. Biodiversity conservation should value not only forest stands and trees that already have many TreMs, but also those where the likelihood of future TreM formation is high due to species, maturity or local environmental conditions. The addition of quantitative models of TreM formation to forest stand dynamics simulators is necessary to better take into account biodiversity conservation in forest management.
... According to Kraus et al. (2016) there are 64 types of TreMs; recently organized in a hierarchical typology by Larrieu et al. (2018) including "Form"; "Group" and "Type". Their occurrence and frequency are strictly linked to the forest naturalness and aging of trees (Kozák et al., 2018;Paillet et al., 2019;2017). ...
Article
Mediterranean forests are important sources of income for society and represent biodiversity hotspots, characterized by a mosaic of forest structures, from short-rotation even-aged stands to old-growth forests. However, such increased complexity requires forest management to balance timber production with biodiversity conservation at various spatial scales. This study investigated the impacts of forest structures and management alternatives on the occurrence and richness of Tree-related Microhabitats (TreMs) – as proxies for forest biodiversity – in three Mediterranean forests in Italy. The generalized linear mixed model was applied to assess the relationship between a large set of forest structural parameters and the occurrence and richness of TreMs at the tree level, and resulted in an overall model accuracy higher than 80%. The same model was then implemented in hypothetical forest structures, resulting from no management, close-to-nature forestry and combined management system. Results show that at early developmental stages of the stand, no management slightly anticipates the occurrence of TreMs, while in mature forests, the combined forest management system effectively balances forest productivity with biodiversity conservation. The close-to-nature management system is recommended for promoting TreMs richness. Such findings might be used to support sustainable forest management and valorise the multifunctional role of Mediterranean forests.
... • Surrounding microhabitat structures: the number of microhabitat structures in trees according to Kraus et al. (2016) in a 30 m radius around each tree hollow: woodpecker holes, visible tree fungi, broken branches with a minimum diameter of 12 cm, and injuries to the bark with a minimum area of 250 cm 2 . These tree-related microhabitat structures have been widely recognized as important substrates and structures for saproxylic biodiversity in forests and are receiving increasing attention in management, conservation and research (Larrieu et al., 2018). ...
Article
Full-text available
Tree hollows are among the rarest habitats in today's Central European managed forests but are considered key structures for high biodiversity in forests. To analyze and compare the effects of tree hollow characteristics and forest structure on diversity of saproxylic beetles in tree hollows in differently structured managed forests, we examined between 41 and 50 tree hollows in beech trees in each of three state forest management districts in Germany. During the two-year study, we collected 283 saproxylic beetle species (5880 individuals; 22% threatened species), using emergence traps. At small spatial scales, the size of hollow entrance and the number of surrounding microhabitat structures positively influenced beetle diversity, while the stage of wood mould decomposition had a negative influence, across all three forest districts. We utilized forest inventory data to analyze the effects of forest structure in radii of 50–500 m around tree hollows on saproxylic beetle diversity in the hollows. At these larger spatial scales, the three forest management districts differed remarkably regarding the parameters that influenced saproxylic beetle diversity in tree hollows. In Ebrach, characterized by mostly deciduous trees, the amount of dead wood positively influenced beetle diversity. In the mostly coniferous Fichtelberg forest district, with highly isolated tree hollows, in contrast, only the proportion of beech trees around the focal tree hollows showed a positive influence on beetle diversity. In Kelheim, characterized by mixed forest stands, there were no significant relationships between forest structure and beetle diversity in tree hollows. In this study, the same local tree hollow parameters influenced saproxylic beetle diversity in all three study regions, while parameters of forest structure at larger spatial scales differed in their importance, depending on tree-species composition.
... Vegetation cover, including the herb and shrub layer, was measured on eight 25 m 2 subplots, systematically placed in every plot. In addition, data on tree-related microhabitats (TreMs) were collected based on a detailed typology proposed by Larrieu et al. (2018). TreMs are usually grouped into seven forms, including cavities, tree injuries and exposed wood, crown deadwood, excrescences, fruiting bodies of saproxylic fungi and slime molds, epiphytic, epixylic and parasitic structures, and fresh exudates such as sap run and heavy resinosis (Asbeck et al., 2021). ...
Article
The variability in the amount and configuration of broad habitat types in the landscape, together with their structural complexity, influence observed biodiversity patterns. When considering structurally similar sites of the same habitat type, the variability in the abundance, species richness or diversity of organisms may be explained by the landscape context. To assess the numerical response of species to the landscape context, in terms of amount and configuration of forest environments, we investigated the bird assemblages of similarly structured forest habitats in an extensively managed forest region, encompassing different landscape contexts. We considered the numerical response of bird assemblages, in terms of abundance, species richness and diversity, and relative abundance of specific guilds, to the landscape context. We considered the forest cover at different spatial scales as a measure of habitat amount, while we quantified aspects of habitat configuration using various landscape metrics, and measured local forest structures. We found significant responses in multiple forest bird species to three important indices of forest structures: mean diameter of living trees, mean diameter of dead trees and volume of lying deadwood. Within similarly structured forest plots, bird assemblages showed responses linked with the landscape context, while plots with different habitat structure showed similar responses to the landscape context. In particular, there was a clear positive response of birds to the amount of broadleaf and mixed forest cover in the landscape. In addition, the distance between forest patches negatively affected species richness and diversity. Within landscapes, the increase of broadleaf in the existing forest area could boost abundance and diversity, decrease isolation levels for species dependent on broadleaves and enhance structural connectivity, generally favouring the majority of the species. Our findings suggest that the simple provision of habitat structures cannot represent a viable solution for biodiversity conservation and that the use of structural indicators of biodiversity like deadwood and age of canopy trees for assessing conservation value of forest needs to be integrated with landscape-scale indices. Our analysis clearly shows that the amount of habitat available in the surrounding landscape is linked with positive biodiversity responses. As human activities can alter both the provision of important habitat structures in stands across the landscape, as well as their overall landscape context, an integrated multi-scale biodiversity management is highly advisable.
... The 15 trees (not considering tree species identity) with the largest crown area according to aerial images (and therefore largest dbh) were designated as potential habitat trees (HT), defined as live or dead standing trees that provide tree-related microhabitats, e.g. cavities, large dead branches, loose bark (Storch et al., 2020), which were examined according to Larrieu et al. (2018). More detailed information about habitat tree selection is given in Asbeck et al. (2019) and Storch et al. (2020). ...
Article
Lacking structural diversity in production forests has been evidenced to decrease epiphytic bryophytes and lichens. One approach to create structurally more diverse forests is retention forestry. Only a small number of studies focused on the effectiveness of retention measures in continuous-cover forestry. Most studies have been conducted in even-aged, clear-cut based management systems and applied different approaches, but they all have in common that the retained trees have been examined for epiphytes only after harvest. Thus, it remains unclear whether these trees or even a certain tree species could take the lifeboat function for epiphytes on logged sites. Thus, prior to logging, we assessed epiphytic bryophytes and lichens on potential large living retention trees, here referred to as habitat trees (HT), of Abies alba and compared the diversity pattern to nearby average trees (AT; A. alba, Fagus sylvatica or Picea abies) of smaller sizes in selectively harvested continuous-cover forests. Selection of AT was based on the average stem diameter of all trees within the stand. We found that species richness and Simpson diversity of lichens were significantly higher on HT. For bryophytes, F. sylvatica AT showed significantly higher Simpson diversity. Mixed models revealed positive effects of F. sylvatica on bryophytes, whereas large stem diameters and elevation were the driving forces for lichens. Additionally, ordinations revealed clear patterns in species composition separating between conifers and broadleaved trees, and along increasing altitude and stem diameter. Concerning HT selection, we suggest to focus rather on the tree species diversity than on stem diameter, when aiming to protect epiphytic bryophytes and lichens.
... Structurally, snags provide unique ecological substrates for wildlife in breeding, roosting and foraging (Bunnell et al., 1999;Cockle et al., 2011;Drever et al., 2008;Gentry & Vierling, 2008;Martin & Eadie, 1999;Mikusiński et al., 2001), with species reliant on the standing deadwood or microhabitats contained within (including nest cavities, bark fissures and other structures; Asbeck et al., 2020;Larrieu et al., 2018;Martin et al., 2004). Snags serve as useful indicators of biodiversity Michel & Winter, 2009;Paillet et al., 2017), with snag densities and distributions supporting an array of species across many taxonomic groups, including birds, mammals, amphibians, reptiles (Bunnell et al., 1999;Drever et al., 2008;Drever & Martin, 2010;Martin et al., 2004;Titus, 1983), invertebrates (Bunnell et al., 1999;Hanula et al., 2006;Janssen et al., 2011) and fungi (Bunnell et al., 1999;Jackson & Jackson, 2004). ...
Article
Full-text available
Airborne lidar is often used to calculate forest metrics about trees but it may also provide a wealth of information about the space between trees. Forest canopy gaps are defined by the absence of vegetative structure and serve important roles for wildlife, such as facilitating animal movement. Forest canopy gaps also occur around snags, keystone structures that provide important substrates to wildlife species for breeding, roosting, and foraging. We wanted to test a method for quantifying canopy gaps around individual snags and live trees, with the working hypothesis that snags would have more gaps surrounding them overall than live trees. We evaluated canopy gaps around individual snags (n=270) and live trees (n=2186) and evaluated correlations between canopy structure and snag occurrence in dense conifer stands of the Idaho Panhandle National Forest, USA. We paired airborne lidar with ground reference data collected at fixed‐radius plots (n=53) to evaluate local gap structure. The R package ForestGapR was used to quantify canopy gaps throughout the canopy to determine where the differences were greatest. A canopy space profile was created for each tree by mapping gaps (a) vertically every 2 m in height (2–50 m above ground), and (b) horizontally across small (16 m2), medium (36 m2), and large (64 m2) footprint sizes. Our results suggest this method is robust for quantifying canopy gaps around individual trees. The canopy space profiles were distinctly different for snags and live trees, with more canopy gaps within the area surrounding snags relative to live trees. The greatest differences occurred at mid‐canopy heights (~20 m above ground) and at the smallest footprint size (16 m2). These results show potential to improve understanding of gap dynamics in closed‐canopy conifer forests, and we suggest snag modeling could be improved by incorporating lidar‐derived canopy gap analyses alongside existing methodologies.
... However, forest inventories can be used as reliable indicators of biodiversity only if they measure specific structural attributes with evident causal importance for specific groups of organisms (Barton et al., 2020). Some useful approaches based on deadwood amount, type and decay class (e.g., Lassauce et al., 2011) or, recently, on tree related microhabitats (Larrieu et al., 2018) have been suggested. However, these structural variables only partially inform about the diversity and composition of different taxonomic groups since their responses to environmental conditions are variable and complex (Larrieu et al., 2019;Paillet et al., 2018). ...
Article
Full-text available
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 Euro-pean 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 1 ORCID
... However, forest inventories can be used as reliable indicators of biodiversity only if they measure specific structural attributes with evident causal importance for specific groups of organisms (Barton et al., 2020). Some useful approaches based on deadwood amount, type and decay class (e.g., Lassauce et al., 2011) or, recently, on tree related microhabitats (Larrieu et al., 2018) have been suggested. However, these structural variables only partially inform about the diversity and composition of different taxonomic groups since their responses to environmental conditions are variable and complex (Larrieu et al., 2019;Paillet et al., 2018). ...
Article
Full-text available
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.
... Tree-related microhabitats (TreM) have been shown to be crucial for promoting biodiversity in forests and have therefore become an important measure for forest conservation and management (Asbeck et al., 2021). One type of TreM that occurs throughout the vertical extent of trees is the water-filled tree hole or dendrotelma (Kitching, 2000;Larrieu et al., 2018). Gossner et al. (2016) showed that water-filled tree holes can occur in large numbers in the canopy but also near the ground. ...
Article
Full-text available
Forest ecosystems have a distinct vertical dimension, but the structuring of communities in this three-dimensional space is not well understood. Water-filled tree holes are natural microcosms structured in metacommunities. Here, we used these microcosms as model systems to analyze how insect communities and the occurrence and abundance of individual species are influenced by biotic and abiotic microhabitat characteristics, the vertical position of the tree hole, and stand-scale habitat availability. We found that both the characteristics of water-filled tree holes and their insect communities differ significantly between canopy and ground level. Individual insect species showed contrasting responses to the vertical position of the tree holes when important environmental factors at the stand and the tree-hole scale were considered. While some species, such as the mosquito Aedes geniculatus and the beetle Prionocyphon serricornis , decreased in abundance with increasing tree-hole height, the biting midge Dasyhelea sp., the non-biting midge Metriocnemus cavicola and the hoverfly Myiatropa florea increased in abundance. Our results suggest that vertical stratification in forests is most likely driven not only by variation in tree-hole microhabitat properties, i.e., niche separation, but also by individual species traits, such as adult dispersal propensity, food preferences and mating behavior of adult stages, and interspecific competition of larval stages. Therefore, communities of insect species developing in tree holes are likely structured by competition–colonization trade-offs predicted by metacommunity theory.
... Next to standing and lying deadwood, tree-related microhabitats are considered important for biodiversity and become increasingly relevant in forest nature conservation and management (Larrieu et al., 2018). We recorded tree-related microhabitats on 2,000 m² across each plot (five subplots of 20 m × 20 m) following the reference catalogue of Kraus et al. (2016) (Schall et al., 2020). ...
Article
Full-text available
1. 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. 2. 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 unman-aged 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. 3. 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. 4. Synthesis and applications. We see two main conclusions from our study. First, un-managed 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
... We used our RF classi cation model with the PBIA approach to identify the dead crown pixels over large areas around our study plots. Our approach did not allow us to assess dead-tree density so we estimated the cumulative surface area of the dead and dying tree parts, i.e. the dead crowns (Larrieu et al. 2018). We then mapped and summed the dead crown pixels to assess a level of forest dieback over several spatial scales. ...
Preprint
Full-text available
Context: Forest ecosystems worldwide are facing increasing drought-induced dieback, causing mortality patches across the landscape at multiple scales. This increases the supply of biological legacies and differentially affects forest insect communities. Objectives: We analysed the relative effects of local- and landscape-level dieback on local saproxylic beetle assemblages. We assessed how classic concepts in spatial ecology (e.g. habitat-amount and habitat-patch hypotheses) are involved in relationships between multi-scale spatial patterns of available resources and local communities. Methods: We sampled saproxylic beetle assemblages in commercial fir forests in the French highlands. Through automatic aerial mapping, we used dead tree crowns to assess dieback levels at several nested spatial scales. We analysed beetle taxonomic, phylogenetic and functional diversity related to differing levels of multi-scale dieback. Results: In line with the habitat-amount hypothesis, taxonomic and functional diversity, but not phylogenetic diversity, of beetle assemblages significantly benefitted from forest dieback, at both local and landscape scales. Very few single or interaction effects were detected in the multiplicative models combining local and landscape variables, though a significant positive effect of landscape-scale dieback on the abundance of cavity- and fungus-dwelling species was consistent with a spill-over effect. Increased landscape-scale dieback also caused a functional specialisation of beetle assemblages, favouring those related to large-diameter, well-decayed deadwood. Conclusions: Increasing tree mortality under benign neglect provides conservation benefits by heterogenising the forest landscape and enhancing deadwood habitats. Legacy retention practices could take advantage of unharvested, declining forest stands to promote species richness and functional diversity within conventionally managed forest landscapes.
... From an applied perspective, tree holes could, after filling some of the described knowledge gaps, be used as indicator systems of environmental change (Ager et al., 2010;Petermann et al., 2016), especially also in urban areas. Likewise, the presence of tree holes themselves can been used as a tool to assess the habitat quality of forests Kraus et al., 2016;Larrieu et al., 2018). ...
Article
Full-text available
Water‐filled tree holes are unique ecosystems that may occur high up in tree crowns and are essentially aquatic islands in the sky. Insect larvae, mesofauna, and other organisms colonize the waterbodies and feed on the accumulating detritus. Water‐filled tree holes are not only important habitats for these species but have been used as model systems in ecology. Here, we review more than 100 years of research on tree‐hole inhabiting organisms and show that most studies focus on selected or even single species (most of which are mosquitoes), whereas only few studies examine groups other than insects, especially in the tropics. Using a vote counting of results and a meta‐analysis of community studies, we show that the effects of tree‐hole size and resources on abundance and richness were investigated most frequently. Both were found to have a positive effect, but effect sizes were modulated by site‐specific environmental variables such as temperature or precipitation. We also show that parameters such as the height of the tree holes above ground, tree‐hole density, predation, and detritus type can be important drivers of organism abundance or richness but are less often tested. We identify several important research gaps and potential avenues for future research. Specifically, future studies should investigate the structure, functions, and temporal dynamics of tree‐hole food webs and their cross‐system interactions, for example, with terrestrial predators that act as a connection to their terrestrial surroundings in meta‐ecosystems. Global observational or experimental tree‐hole studies could contribute pivotal information on spatial variation of community structure and environmental drivers of community assembly. With a better understanding of these unique aquatic habitats in terrestrial ecosystems, natural and artificial tree holes can not only serve as model systems for addressing fundamental ecological questions but also serve as indicator systems of the impacts of environmental change on ecosystems. Water‐filled tree holes are unique ecosystems that are inhabited by insect larvae, mesofauna and other organisms. In our review and meta‐analysis we show that most studies on tree‐hole inhabitants focus on selected or even single species, and that the few community studies consistently found positive effects of tree‐hole size and resources on abundance and richness of inhabitants, sometimes modulated by environmental parameters such as annual temperature. We identify potential avenues for future research and argue that a better understanding of water‐filled tree holes will facilitate their use as model systems for addressing fundamental ecological questions and as indicator systems of the impacts of environmental change on ecosystems.
... Snag and live tree characteristics differ across multiple dimensions, including the degree of open space occupied, the unique physical structures provided, and the composition and decay status of wood. These combined characteristics contribute to a wide range of forest microhabitats relevant to wildlife, with many microhabitats associated primarily with snags [2,3]. ...
Article
Full-text available
Standing dead trees (known as snags) are historically difficult to map and model using airborne laser scanning (ALS), or lidar. Specific snag characteristics are important for wildlife; for instance, a larger snag with a broken top can serve as a nesting platform for raptors. The objective of this study was to evaluate whether characteristics such as top intactness could be inferred from discrete-return ALS data. We collected structural information for 198 snags in closed-canopy conifer forest plots in Idaho. We selected 13 lidar metrics within 5 m diameter point clouds to serve as predictor variables in random forest (RF) models to classify snags into four groups by size (small (<40 cm diameter) or large (≥40 cm diameter)) and intactness (intact or broken top) across multiple iterations. We conducted these models first with all snags combined, and then ran the same models with only small or large snags. Overall accuracies were highest in RF models with large snags only (77%), but kappa statistics for all models were low (0.29–0.49). ALS data alone were not sufficient to identify top intactness for large snags; future studies combining ALS data with other remotely sensed data to improve classification of snag characteristics important for wildlife is encouraged.
... Furthermore, relict tree stands often contain very old trees (Fazan et al. 2012;Tang et al. 2013;Camarero et al. 2018), and old trees are known to provide numerous microhabitats (Lindenmayer & Laurance 2017;Nordén et al. 2018). These microhabitats (sometimes denominated in literature as 'tree related microhabitats'; Kraus et al. 2016;Larrieu et al. 2018;Bütler et al. 2020) can also be formed by tree-associated taxa such as bryophytes or lichens. Some in turn foster a wide variety of other living organisms (e.g. ...
Article
Full-text available
Trees have a crucial importance in the functioning of ecosystems on Earth. They are among the largest and longest-living taxa and provide habitat and shelter to numerous species belonging to diverse groups of organisms. Relict trees are of particular interest through their history of survival and adaptation, and because they potentially shelter rare or threatened organisms today. We investigated for the first time the diversity and distribution of epiphytic lichens and bryophytes found on the Cretan (Greek) endemic and relict phorophyte Zelkova abelicea (Ulmaceae). Our results showed that Z. abelicea hosts a high number of epiphytes. The Levka Ori mountain range in western Crete seems to be a hot spot for epiphytic lichens on Z. abelicea. Bryophytes had the highest diversity on Mt Kedros in central Crete but were absent from several other sites. Moreover, 17% of the studied lichens were recorded for the first time for Crete and 5% have never been recorded for Greece. Geographical position and browsing intensity seem to be important factors influencing the epiphytic community encountered. Tree morphology (dwarfed or arborescent) was also significant in influencing community composition although it was not possible to dissociate this factor from the effect of topography. Dwarfed individuals were found to have as much epiphytic diversity as arborescent trees. Ecological indicator values showed that high epiphytic diversity was found in some sites despite signs of eutrophication and disturbance due to pastoral activities and suggest the co-occurrence of both disturbance tolerant and sensitive species. Our results show how little is known about the biodiversity of Cretan phorophytes and highlights the need for further research on the topic.
... Vegetation cover, including the herb and shrub layer, was measured on eight 25-2 plots, systematically placed in every site. Further important forest structures included the abundance and richness of Tree-related Microhabitats (TreMs 43,44 ). These microhabitats represent important structures for forest organisms 45,46,82 and include, for instance, woodpecker cavities, trunk and mould cavities, branch holes, water-filled tree holes, insect galleries, bore holes, stem injuries and wounds (e.g., bark loss, or exposed sapwood), crown deadwood, cankers and burrs, epiphytes, nests of vertebrates and invertebrates, and can be used to characterize the forest. ...
Article
Full-text available
Functional diversity is linked with critical ecosystem functions, yet its relationship with numerical diversity, e.g. species richness, is not fully understood. The mechanisms linking changes of species richness, e.g. random and non-random species losses and gains, with changes of functional diversity become more relevant in the face of rapid environmental changes. In particular, non-random species changes including rare species may affect functional diversity, and the overall ecosystem function, disproportionately compared to random species changes including common species. In this study, I investigated how changes in numerical diversity of bird assemblages are related to functional diversity, and how the environment, and in particular forest management, influences such a relationship. I collected bird count data in the extensively-managed forest landscape of the Black Forest (Germany), at 82 sampling sites over three years. Data included species richness and abundance per site, and functional traits related to diet and habitat type for each species to compute functional diversity. By partitioning numerical diversity changes into five components using Price Equations, I calculated the contribution of random and non-random species losses and gains, and the abundance of common species, to functional diversity. Then I modelled these contributions as a function of several environmental variables describing broad forest conditions, and including forest management intensity. I found that, beside the major contribution of random species losses to functional diversity, non-random species losses also play a role, indicating that rare species that contribute more to functional diversity are often lost earlier than common species. The overall contribution to functional diversity of species losses is larger than that of species gains, pointing toward an ongoing simplification of the forest bird assemblage. Among all Price components, random species gains were influenced by management intensity, while other components were not influenced by any management variable. This highlight that potential conservation actions may not be effective in halting ecosystem functioning decline, as species gains do not result in increased functional diversity.
... Jest to jedyny taki przykład z Dolnego Śląska, kiedy gmina objęła ochroną pomnikową młode okazy drzew, którymi uzupełniono aleję. (Blicharska & Mikusiński, 2014;Larrieu et al., 2018;Sobolewski, 2020;Wetherbee et al., 2020), nie widać, by przekładało się to konkretne działania. Najkorzystniej wypadają pod tym względem gminy miejsko-wiejskie, których aktywność w zakresie obejmowania ochroną drzew była najwyższa. ...
Article
Full-text available
Monuments of nature are local forms of nature conservation, which have been established since August 2009 only in the form of a resolution of the local councils. The study uses local acts of law establishing and removing protection from trees in the years 2009–2021 (until August 1st, 2021), published on the official website of the Lower Silesian province. The municipalities of Lower Silesia were reluctant to establish trees as natural monuments in those years. They were more often removing than establishing protection. Urban communes most often removed the protection of trees than rural and urban-rural ones, and it was the urban-rural communes that fared best in this comparison. Almost 40% of trees under protection in the years 2009–2021 in the Lower Silesian province were pedunculate oaks, which were established in almost 80% of communes. The remaining species are of marginal importance as monuments of nature, except for common beech, small-leaved linden and London plane, which together make up about 20% of all new monuments of nature. Due to this fact, it is recommended to establish monuments of nature from a wider range of species. The main reasons for removing protection from trees were “ensuring public safety” and “loss of natural value”. Thus, the question about the meaning of the loss of environmental value according to the legislator. The work presents the issues of protection of trees in Lower Silesia and the conclusions resulting from it may help outline the directions of protection of trees also in other provinces.
... This fits well with the general goal to manage forests for resilience. The retention of habitat trees and deadwood with a focus on Tree-related Microhabitats (TreMs) has become important in forest management (Larrieu et al. 2018;Bütler et al. 2020). ...
Article
Full-text available
What is Closer to Nature Forest Management? Closer-to-Nature Forest Management is a new concept proposed in the EU Forest Strategy for 2030, which aims to improve the conservation values and climate resilience of multifunctional, managed forests in Europe. Building on the latest scientific evidence, this report attempts to define the concept based on a set of seven guiding principles. It also outlines a framework/checklist for flexible European-wide implementationof the concept. The 7 principles of Closer-to-Nature Forest Management are: 1. Retention of habitat trees, special habitats, and dead wood 2. Promoting native tree species as well as site adapted non-native species 3. Promoting natural tree regeneration 4. Partial harvests and promotion of stand structural heterogeneity 5. Promoting tree species mixtures and genetic diversity 6. Avoidance of intensive management operations 7. Supporting landscape heterogeneity and functioning This report analyses the current pressures on forest biodiversity as well as on the health of, and resilience in, managed forests. It examines existing nature-oriented forest management approaches in Europe and analyses their ability to support biodiversity, their stability and adaptability to uncertain future conditions. It proposes a definition, a set of guiding principles and a framework for flexible European-wide implementation of Closer-to-Nature Forest Management. Finally, it evaluates barriers and enablers for implementation and presents a list of existing networks that can be used to assist the dissemination of Closer-to-Nature Forest Management throughout Europe. How can we implement this new concept? 1. Different regions need different management approaches: While the general principles of Closer-to- Nature Forest Management should be similar across all regions, varying but related management approaches should be used in different regions of Europe. This reflects the variation in forest types across the continent, differences in the intensity and scale of natural disturbance regimes, and the ways forests have been used in the past and will have to be managed in the future. 2. Learn from the past and consolidate existing networks and demonstrations: There is a long European tradition of nature-based forest management concepts, and there are many opportunities to learn from existing practices. Because the wider adoption of Closer-to-Nature Forest Management will require a substantial effort in knowledge transfer, it is very important to consolidate existing networks of trials and demonstrations. Such a knowledge transfer network should cover all major regions and forest types found in Europe and could be linked to others seeking to preserve traditional and sustainable management methods, cultural landscapes and their associated biocultural diversity. This will be invaluable in the ongoing social learning process and in helping to convince forest managers and other stakeholders of the benefits of this approach. 3. Use adaptive management as a way to tackle uncertainties: We need to regularly monitor forest responses to management interventions, evaluate these responses and adjust management strategies accordingly. A similar adaptive approach is urgently required to evaluate the impact of policy measures and support mechanisms proposed to encourage adoption of Closer-to-Nature Forest Management. 4. Not a quick-fix, long-term measures are needed: The introduction of Closer-to-Nature Forest Management is not a ‘quick-fix’ and policy makers must provide long-term and consistent support measures to encourage forest managers and other stakeholders to adopt this strategy. Support for forest owners for training and application of the strategy is key. 5. Review existing subsidy and taxation regimes for private owners: Convincing private owners to follow this approach will require the creation of schemes that reward them for providing ecosystem services. Closer-to- Nature Forest Management has the potential to support biodiversity, adapt forests to climate change and provide ecosystem services to a higher level than conventional forest management. There is an urgent need to review existing subsidy and taxation regimes affecting private forestry, and to consider how these might be changed to further the uptake of Closer-to-Nature Forest Management. 6. Develop and use new technologies and tools: There is a need to harmonize monitoring systems and to develop and use new technologies and tools (GIS, GPS and remote sensing) to ease management of these more diverse and structure-rich forests. Finally, there are still some uncertainties about the effect of certain elements of Closer-to-Nature Forest Management on biodiversity conservation and ecosystem health, and how they will affect other ecosystem services including wood production under different management conditions throughout Europe. This calls for more collective learning, experimentation and research.
... Tree microhabitats were identified and measured as per the catalog by (Kraus et al., 2016) and were 151 grouped into seven forms, 15 groups, and 47 types (Larrieu et al., 2018). In addition, tree microhabitats 152 in the upper parts of the trees were identified with binoculars (Zeiss Terra ED 8x42). ...
Article
Full-text available
Trees in cities provide multiple ecosystem services. However, simultaneously ensuring healthy trees with high habitat diversity can be challenging in a harsh urban environment. We compared health, microhabitats, and bat activities between native ( Quercus robur L.) and non-native ( Quercus rubra L.) oaks growing in different urban habitats (street vs. park) in Karlsruhe, southwestern Germany. We randomly selected 167 oak trees with a diameter at breast height (DBH) greater than 20 cm across the city from Urban Tree Registrar. We performed tree health assessment, dendrometric, and microhabitat inventory. We recorded the bat activities for four days on 45 native and non-native oaks with acoustic loggers installed on the trees. We found that non-native oaks were healthier than native oaks but provided less abundance and richness of microhabitats. Tree size (positive effect) and pruning (negative effect) strongly influence microhabitat richness and abundance. In addition, park trees hosted significantly more microhabitats than street trees. We recorded the activities of 9 bat species from 4 genera. Pipistrellus bats were more active in park trees than street trees. Long-eared bats ( Plecotus ) were more active near the native than non-native oaks. Bats are likely favored by microhabitats such as fork split, lightning scar, and woodpecker "flute" that are more common in less healthy trees. We conclude that non-native red oak can be planted alongside streets, where the conditions are harsher than in parks, to better adapt to climatic changes and stay healthy with less maintenance. The preservation of native pedunculate oak trees, especially within parks, is paramount for urban biodiversity conservation because of their potential to provide microhabitats and supporting bats.
... The age of a (potential) host is considered a decisive determinant affecting the abundance of epiphytes in a twofold manner. First, as trees grow bigger with increasing age, they provide more surface area and more diverse microhabitats, where suitable substrates slowly accumulate over time (Jarman & Kantvilas, 1995;Larrieu et al., 2018;Paillet et al., 2019;Vuidot et al., 2011;Woods et al., 2015;Zotz & Vollrath, 2003). Consequently, suitable microhabitats for accidental epiphytes are most common on old and structurally diverse trees. ...
Article
Vascular epiphytes are an important component of many ecosystems and constitute a substantial part of global plant diversity. In this context, accidental epiphytism, i.e. the opportunistic epiphytic growth of typically terrestrial species, deserves special attention as it provides crucial insights into the global distribution of vascular epiphytes and the initial evolution of epiphytic lineages. Even though accidental epiphytes have been mentioned in the literature for more than a century, they have been neglected in most epiphyte studies. Only recently accidental epiphytism was investigated more thoroughly. Therefore, the aim of this article was to provide a comprehensive review of the ecological basis and the evolutionary relevance of this common but largely disregarded phenomenon and to highlight open questions and promising research directions. Our central statement that potentially any species could grow epiphytically given the availability of suitable microhabitats and successful dispersal is backed up by a compilation of observations of accidental epiphytes from numerous ecosystems with diverse climates, even including semi‐arid Mediterranean ones. There are a variety of arboreal microhabitats with environmental conditions conforming to the ecological niche of typical terrestrial species, with the availability of such microhabitats depending on the interaction of local climate conditions, host tree age and host species identity. Whenever suitable microhabitats are available in tree crowns, accidental epiphytism is primarily limited by dispersal. In an evolutionary context, the conquest of the forest canopy represents an ecological opportunity where accidental epiphytes act as link between the terrestrial and the epiphytic life form. We discuss two fundamental scenarios with sympatric speciation, selective pressure, autopolyploidy, and allopatric speciation as underlying mechanisms in the transition from terrestrial to epiphytic growth. In conclusion, we argue that accidental epiphytism is a substrate and dispersal dependent phenomenon and that both from an individual perspective and from an evolutionary perspective epiphytism reflects the occupation of suitable but previously unexploited arboreal microhabitats. Acknowledging the fundamental principles that plant growth is opportunistic and that dispersal is a stochastic process can decisively improve our understanding of species distributions and other ecological patterns, as in the case of accidental epiphytism.
... Hence, without having information about the life history traits of each recorded species, it can be expected that species captured in stem emergence traps are in fact either obligate or facultative saproxylic. Yet, [obligate] saproxylic species are highly specialized and, in addition to deadwood, exploit specific tree-related microhabitats such as tree cavities or fungal fruiting bodies (Larrieu et al., 2018;Siitonen, 2001). Facultative saproxylic species use both deadwood and treerelated microhabitats opportunistically, where they can feed on the accumulating detritus, sap exudates or other arthropods or use them as oviposition, hibernation or aestivation site (Alexander, 1994;Speight, 1989;Ulyshen, 2018;Yoshimoto et al., 2005). ...
Article
How many species can live in a specific habitat is a key question in conservation biology. Due to its heterogeneity, deadwood supports highly diverse communities. The total number of species related to deadwood is, however, underestimated by most empirical community studies. First, as most reports on saproxylic species richness do not relate the number of species observed to the sample size used, it is not possible to draw conclusions about the representativeness of the species richness observed. Secondly, the assessment of species richness is usually limited to obligate saproxylic species, i.e., species classified by experts as being strictly dependent on deadwood. Hence, many species are ignored that can be considered facultative saproxylic; i.e., they are not dependent on deadwood but clearly benefit from it. The present study aims to statistically estimate the proportion of obligate and facultative saproxylic species among Coleoptera, Arachnida and Heteroptera in a European mountain forest. Therefore, we applied rarefaction/extrapolation based on sample coverage estimators, using data from an experimental approach including three trapping methods. The estimates suggest that obligate and facultative saproxylic beetles account for 28% and 19% of the total species richness of beetles, respectively. The estimated proportion of obligate saproxylic Heteroptera and Arachnida species was 4% and 12%. Facultative saproxylics were estimated to account for 24% and 69% of the total species richness, respectively. In summary, our study shows that the share of arthropod diversity related to deadwood is about 50 to 70%, within the three taxa Coleoptera, Arachnida and Heteroptera in a temperate forests temperate mountain forest, which is higher than previously assumed. This highlights the importance of deadwood for forest biodiversity and further supports deadwood restoration activities.
... TreMs inventories can provide an estimate of species richness in forests as they represent the presence of certain ecosystems on the tree trunk (Courbaud et al., 2022). In order to provide a standardized definition of TreMs, (Larrieu et al., 2018) proposed a classification of 47 TreMs forms into 7 groups and 15 sub-categories. (Brändli et al., 2021) further simplified the classification of TreMs to the 19 most significant species in terms of their occurrence and importance in Switzerland. ...
Article
Full-text available
In the last few years, a number of low-cost 3D scanning sensors have been developed to reconstruct the real-world environment. These sensors were primarily designed for indoor use, making them highly unpredictable in terms of their performance and accuracy when used outdoors. The Azure Kinect belongs to this category of low-cost 3D scanners and has been successfully employed in outdoor applications. In addition, this sensor possesses features such as portability and live visualization during data acquisition that makes it extremely interesting in the field of forestry. In the context of forest inventory, these advantages would allow to facilitate the task of tree parameters acquisition in an efficient manner. In this paper, a protocol was established for the acquisition of 3D data in forests using the Azure Kinect. A comparison of the resulting point cloud was performed against photogrammetry. Results demonstrated that the Azure Kinect point cloud was of suitable quality for extracting tree parameters such as diameter at breast height (DBH, with a standard deviation of 2.2cm). Furthermore, the quality of the visual and geometric information of the point cloud was evaluated in terms of its feasibility to identify microhabitats. Microhabitats represent valuable information on forest biodiversity and are included in Swiss forest inventory measurements. In total, five different microhabitats were identified in the Azure Kinect Point cloud. The measurements were therefore comparable to sensors such as terrestrial laser scanning and photogrammetry. Therefore, we argue that the Azure Kinect point cloud can efficiently identify certain types of microhabitats and this study presents a first approach of its application in forest inventories.
... Forest structure, tree species composition, deadwood volume, abundance, and diversity of microhabitats are essential factors influencing biodiversity in forest ecosystems (Paillet et al., 2010;Müller et al., 2012;Regnery et al., 2013;Parisi et al., 2020a). Indeed, many saproxylic species depend on tree microhabitats for food, shelter, and breeding (Vuidot et al., 2011;Larrieu et al., 2018;Parisi et al., 2020b). Although ecological studies on saproxylic beetle communities in southern Europe have increased in recent years (Gossner et al., 2016;Lachat et al., 2016;Lelli et al., 2019;Parisi et al., 2016Parisi et al., , 2019Parisi et al., , 2020aParisi et al., , 2020bVogel et al., 2020aVogel et al., , 2020b, there are relatively few studies on saproxylic organisms in managed mountain forest ecosystems (Siitonen, 2001;Parisi et al., 2020a). ...
Article
Full-text available
Background Rapid climate changes lead to an increase in forest disturbance, which in turn lead to growing concerns for biodiversity. While saproxylic beetles are relevant indicators for studying different aspects of biodiversity, most are smaller than 2 mm and difficult to sample. This, together with a high number of species and trophic roles, make their study remarkably challenging, time-consuming, and expensive. The Landsat mission provides data since 1984 and represents a powerful tool in this scenario. While we believe that remote sensing data cannot replace on-site sampling and analysis, in this study we aim to prove that the Landsat Time Series (TS) may support the identification of insects’ hotspots and consequently guide the selection of areas where to concentrate field analysis. Methods With this aim, we constructed a Landsat-derived NDVI TS (1984–2020) and we summarised the NDVI trend over time by calculating eight Temporal Metrics (TMs) among which four resulted particularly successful in predicting the amount of saproxylic insects: (i) the slope of the regression line obtained by linear interpolating the NDVI values over time; (ii) the Root Mean Square Error (RMSE) between the regression line and the NDVI TS; (iii) the median, and the (iv) minimum values of the NDVI TS. The study area consists of four monitoring sectors in a Mediterranean-managed beech forest located in the Apennines (Molise, Italy), where 60 window flight traps for flying beetles were installed. First, the saproxylic beetle's biodiversities of monitoring sectors were quantified in terms of species richness and alpha-diversity. Second, the capability of TMs in predicting the richness of saproxylic beetles family and trophic categories was assessed in terms of Pearson's product-moment correlation. Results The alpha diversity and species richness analysis indicate dissimilarities across the four monitored sectors (Shannon and Simpson's index ranging between 0.67 to 2.31 and 0.69 to 0.88, respectively), with Landsat TS resulting in effective predictors for estimating saproxylic beetle richness. The strongest correlation was reached between the Monotomidae family and the RMSE temporal metric (R = 0.66). The mean absolute correlation (r) between the NDVI TMs and the saproxylic community was 0.46 for Monotomidae, 0.31 for Cerambycidae, and 0.25 for Curculionidae. Conclusions Our results suggest that Landsat TS has important implications for studying saproxylic beetle distribution and, by helping the selection of monitoring areas, increasing the amount of information acquired while decreasing the effort required for field analysis.
Article
Full-text available
Species richness, abundance and biomass of insects have recently undergone marked declines in Europe. We metabarcoded 211 Malaise-trap samples to investigate whether drought-induced forest dieback and subsequent salvage logging had an impact on ca. 3000 species of flying insects in silver fir Pyrenean forests. While forest dieback had no measurable impact on species richness, there were significant changes in community composition that were consistent with those observed during natural forest succession. Importantly , most observed changes were driven by rare species. Variation was explained primarily by canopy openness at the local scale, and the tree-related microhabitat diversity and deadwood amount at landscape scales. The levels of salvage logging in our study did not explain compositional changes. We conclude that forest dieback drives changes in species assemblages that mimic natural forest succession, and markedly increases the risk of catastrophic loss of rare species through homogenization of environmental conditions.
Article
Full-text available
Tree-related microhabitats (TreMs) are among the most important structural components of a forest, and have a significant impact on biodiversity and influence ecosystem functioning. Although forests that depend on natural lowland water regimes are severely endangered worldwide, and floodplain forests are considered to be the most complex and biologically rich habitats in the temperate zone, the TreMs in them have yet to be identified. This study investigates the assemblage of TreMs in natural Willow-Poplar riparian forests and analyses the environmental factors that influence their qualitative and quantitative compositions. A total of 90 sample plots (0.05 ha each) were selected at random in old-growth riparian forests that occur along a large unregulated river, the Vistula (Poland). A total of 62 TreM types were identified with a mean number of 16.0 ± 4.6 SD TreM types per plot and a mean density of 829.4 ± 360.1 SD TreM-bearing trees ha⁻¹. The number of TreMs found on an individual tree depends on its diameter, the number of trunks, its living status (living vs. dead tree) and the species it belongs to. The richness, density and diversity of TreMs found on a plot depends on the density of living trees, the basal area of living or dead trees, the number of tree species, and the percentage of Willows Salix sp. or of multi-trunk trees. Our study records for the first time the assemblage of TreMs in natural Willow-Poplar riparian forests and provides a reference for floodplain habitats. The results indicate that multi-species forests influenced by natural waterflow-related disturbances are hot-spots of TreM richness and abundance, and highlight the urgent need for the protection or restoration of these vanishing habitats.
Article
Full-text available
Numerous bird species, often rare or endangered, rely on the presence of standing and downed deadwood for shelter, nesting, and foraging. Habitat quality was evaluated on the basis of deadwood volume, the density of large standing deadwood, and the space filling index (SFI). The SFI reflects the degree of space filling of the bottom layers taking into account tree trunks, seedlings, saplings, ground vegetation, stumps, and downed deadwood. Analysis encompassed all special protection areas (SPAs) in Poland (a total of 107 SPAs containing 7974 sample plots monitored under the National Forest Inventory). An additional in-depth analysis was conducted for 30 SPAs with the greatest share of forest habitats. The studied indicators varied substantially both between and within individual SPAs, with deadwood volume ranging from 1.3 to 50.5 m 3 ha −1 (mean of 9.0 m 3 ha −1) and the density of large standing deadwood (diameter at breast height ≥ 30 cm) from 0.1 to 16.0 ind ha −1 (mean of 2.2 ind ha −1). These values were relatively low compared to the density of living trees with corresponding dimensions (111 ind ha −1). SFI analysis indicated high or very high space filling of the bottom forest layers on 14-56% of sample plots in a given SPA. The presence of deadwood was found to be significantly positively affected by SPA location in the mountains, a greater proportion of sites with higher fertility, a greater share of forest area under strict protection, as well as higher stand volume within a given SPA. The correlation between deadwood volume and the density of birds (primary and secondary cavity nesters) in individual SPAs was positive (R = 0.60). As compared to lowland areas, SPAs in mountain areas are generally characterized by high stand volumes, a greater density of large living trees, and a greater amount of diverse deadwood. In those areas conservation measures should involve continuous monitoring and diagnosing of any problems associated with the populations of individual bird species; focused efforts should be implemented to support those species that exhibit unfavorable population trends. In most lowland SPAs measures aimed at the improvement of site conditions for birds must be more extensive than in the mountains, with a low abundance of dead trees (especially large ones). These parameters can be improved by retaining some senescent stands in managed forests until their natural death and implementing a strict protection regime in areas of high conservation value.
Article
Full-text available
The impact of forest management on biodiversity is difficult to scrutinize along gradients of management. A step towards analyzing the impact of forest management on biodiversity is comparisons between managed and primary forests. The standardized typology of tree-related microhabitats (TreMs) is a multi-taxon indicator used to quantify forest biodiversity. We aim to analyze the influence of environmental factors on the occurrence of groups of TreMs by comparing primary and managed forests. We collected data for the managed forests in the Black Forest (Germany) and for the primary forests in the Western (Slovakia) and Southern Carpathians (Romania). To model the richness and the different groups of TreMs per tree, we used generalized linear mixed models with diameter at breast height (DBH), altitude, slope and aspect as predictors for European beech ( Fagus sylvatica (L.)) , Norway spruce ( Picea abies (L.) ) and silver fir ( Abies alba (Mill.) ) in primary and managed temperate mountain forests. We found congruent results for overall richness and the vast majority of TreM groups. Trees in primary forests hosted a greater richness of all and specific types of TreMs than individuals in managed forests. The main drivers of TreMs are DBH and altitude, while slope and aspect play a minor role. We recommend forest and nature conservation managers to focus: 1) on the conservation of remaining primary forests and 2) approaches of biodiversity-oriented forest management on the selection of high-quality habitat trees that already provide a high number of TreMs in managed forests based on the comparison with primary forests.
Article
Full-text available
Forests cover 30% of the Earth's landmass, host 80% of the biodiversity on land, and represent one of the main sinks of carbon. Studying forest ecosystems and dynamics is more crucial than ever now that the climate is changing. On the other hand, forest structural attributes and microhabitats data acquisition is challenging, and require huge efforts. Here we provide a georeferenced dataset of living trees, deadwood, and microhabitats referring to 199 plots (13 m radius), collected between 2012 and 2018, and located over six Apennine mountainous forest types across Italy. The dataset we provide promotes collaboration among researchers and improves the possibilities to analyze the evolution of forest ecosystems.
Article
Full-text available
Background and Objectives: In recent years the protection of biodiversity became an important goal in forest management and caused some conservativem management approaches such as creating protected areas or areas in which no management has been implemented. In the last decade, habitat trees came under focus. Micro habitats are structures on dead or alive trees in the forest including changes such as wounds and fractures caused by biological processes and provide places for forest living organisms. Nowadays the necessity of habitat tree protection has been emphasized in forest management and policies. This study aimed to assess the diversity and frequency of tree micro habitats in Persian ironwood- hornbeam forest stands at Bahramnia Forestry Plan (Gorgan). Materials and Methods: Therefore for assessing the trees’ micro-habitats 4 square sample plots each one with an area of 2500 m2 were selected and allometric characteristics (diameter and height) of all trees with a diameter more than 7.5 cm were recorded. Then according to an instruction the type and abundance of micro-habitats were assessed and recorded for all trees. A binocular was used for assessing the micro-habitats located on top of the tree crown and their upper trunk. The habitat value, as well as the economic value of all trees, have been calculated. A correlation test was used to assess the relationship between occurrence and frequency of micro-habitat with quantitative characteristics of all trees. Results: The result showed that the studied stand is an uneven-aged stand and the Persian-ironwood tree species is the most abundant tree species within it. The hornbeam trees have the highest average diameter and height, as well as the highest diversity and frequency of micro habitats. The most frequent micro-habitats observed on the trees were EP, GR, and CV. The result of the correlation test showed a significant relationship between tree diameter and micro-habitat abundance. By increasing the tree diameter the number of micro-habitats significantly increased. Conclusion: Totally the results of this study show that there are different kinds of micro-habitats in the studied forest stands. Also, the tree diameter is one of the factors that affect micro-habitat abundance. Therefore it is of importance to maintain some of the high diameter trees in the forest stand. Understanding the effective factors on occurrence and abundance of the micro-habitats can be an important help in protecting forest biodiversity.
Article
Full-text available
Large trees are keystone structures for the functioning and maintenance of the biological diversity of wooded landscapes. Thus, we need a better understanding of large-tree-other-tree interactions and their effects on the diversity and spatial structure of the surrounding trees. We studied these interactions in the core of the Białowieża Primeval Forest-Europe's best-preserved temperate forest ecosystem, characterized by high abundance of ancient trees. We measured diameter and bark thickness of the monumental trees of Acer platanoides L., Carpinus betulus L., Picea abies (L.) H. Karst, Quercus robur L., and Tilia cordata Mill., as well as the diameter and distance to the monumental tree of five nearest neighbor trees. The effects of the monumental tree on arrangements of the surrounding trees were studied with the help of linear models. We revealed that the species identity of a large tree had, in the case of C. betulus and T. cordata, a significant impact on the diversity of adjacent tree groupings, their distance to the central tree, and frequency of the neighboring trees. The distance between the neighbor and the large trees increased with the increasing diameter of the central tree. Our findings reinforce the call for the protection of large old trees, regardless of their species and where they grow from the geographical or ecosystem point of view.
Preprint
Full-text available
Tree cavities are an essential resource for cavity-dwelling mammals, birds, invertebrates and fungi, and so they are important for maintaining forest biodiversity. In North American forests, woodpeckers (Picidae) play a keystone role in cavity creation by excavating holes. However, in European forests many hole-nesting songbirds rely on non-excavated cavities that are formed by processes of fungal decay and compartmentalization after tree damage. Several factors are recognised in initiating non-excavated cavities that are used by hole-nesting birds, including loss of a tree branch or stem breakage, but this topic is poorly studied. Here, we propose that bark stripping by large herbivores (e.g. Red Deer Cervus elaphus and European Bison Bison bonasus) could be another important, and previously overlooked, mechanism for initiating tree cavities that are used by hole-nesting birds. We suggest that, after the initial damage from herbivore bark-stripping, fungal decay can create specific elongated, slit-like cavities, which are particularly important as nest sites for some common forest songbirds. We outline this idea using original observations and evidence from the literature, primarily from the primeval forest in Poland’s Białowieża National Park. We also use studies from elsewhere in Europe to show a generally low usage of slit cavities by birds where large herbivores are scarce or absent. We suggest that restoring such animals in European forests could help to restore the abundance and diversity of the tree cavity resource for hole-dwelling species. We encourage future research to investigate this proposal of large herbivores being important agents of tree cavity formation that could enhance biodiversity. A revised version is accepted by Acta Ornithologica July 2022 (in press).
Article
Full-text available
Es presenten els principals criteris a tenir en compte a la identificació d'arbres d'alt valor, econòmic o ecològic, en el marc de la silvicultura orientada a l'arbre, a partir de l'experiència obtinguda de la seva aplicació en una vintena de rodals de formacions mediterrànies i la seva discussió amb experts. Treball realitzat en el marc del projecte LIFE MixForChange, cofinançat per la Comissió Europea, amb la participació del Centre de la Propietat Forestal, el Centre de Ciència i Tecnologia Forestal de Catalunya i les associacions de propietaris de la Serra de Bellmunt-Collsacabra i del Montnegre i el Corredor.
Thesis
Full-text available
Forests are undergoing through a slow but steady process of forest area change, which happen to be different across countries. Predictions of future scenarios highlight the role of agriculture in shaping land-use change in Europe, with possible local benefits for forests. Thus, the role of management in shaping the forests of the future will increase according to the World’s demand for timber, clean water, biodiversity, clean air and other ecosystem services. Research is testing and developing new management strategies to halt completely biodiversity loss. The threats faced by biodiversity in managed forests constitute the challenges of future forest ecological research. The response of birds to environmental changes is a consequence of the close-knit species-habitat relationships they evolved and are adapted to. Adaptations to the forest environment are structural, behavioural and physiological. The alteration of the forest structures and their spatial allocation across landscapes creates threats to bird populations that need to be taken into account in conservation-oriented forest management. The present thesis aims to assess the numerical response of the bird assemblage to forest structures and its relevance for management. The general aim is focused on close-to-nature forest management and on the retention of structural elements as a conservation tool. The numerical response of the bird assemblage is investigated in terms of species diversity and abundance. The general aim is achieved by focusing on the following research questions: i. Which forest and landscape characteristics best explain the abundance and diversity of forest birds? ii. Which management practices can be developed for the conservation of birds in managed forests? This thesis is carried out within the framework of the ConFoBi Research Training Group (Conservation of Forest Biodiversity in multiple-use landscape of Central Europe). ConFoBi assesses whether and how structural retention measures contribute to the conservation of forest biodiversity in multiple-use landscapes of the temperate zone. The research programme of the present thesis has been implemented in the southern Black Forest, Germany, as a model system for temperate forests. The Black Forest is a forest-dominated low mountain range within a multiple-use landscape typical of central Europe, where 135 quadratic 1-ha-plots where selected within the forested areas. Plots were selected along two major environmental gradients: forest vertical complexity, represented by the number of standing dead trees found in each plot; landscape composition, represented by the amount of forest cover within 25 km2 surrounding each plot. All plots were inventoried by measuring the diameter of every tree (above 7 cm diameter at breast height) and the amounts of laying and standing dead wood. Because habitat trees are an important structural element in retention approaches, for each study plot the 15 largest trees were mapped and their existing microhabitats (such as hollows, cracks, and cavities) quantified. Landscape patterns were described using a range of metrics, including amount of forest cover and landscape metrics. Bird data were collected by employing point counts performed at the centre of each plots and repeated two or three times per sampling season (2017-2018). Abundance and diversity of birds were analysed using hierarchical N-mixture models and generalized linear (mixed) models, respectively. The results highlight that current retention practices are well below the retention levels needed by the bird assemblage to have abundance and diversity similar to those of unharvested forests, assessing the levels around 40-60% of retained trees. Retention practices can, however, be improved by retaining trees of higher ecological importance. Trees with a diameter 20 cm larger than the surrounding trees, with cavities, rot holes or concavities can potentially fulfill the habitat requirments of a large array of species, including woodpeckers and the related cavity-users community. The presence of those trees across the landscape can ensure the continuity of resources, while favouring more natural tree species composition will benefit bird species diversity. The response of the entire bird assemblage to the configuration of forest patches indicates that in landscapes with less aggregated forest patches, the abundance of the bird assemblage can potentially be lower than in landscapes with closer forest patches. I conclude that the establishment and assemble of the bird community is a hierarchical spatial process. Small environmental elements determine the occurrence and observed abundance of populations. The location of such elements determines which species and how many individuals of each species are found across the landscape. Over the entire landscape, the amount of available habitat and its configuration determines how many species can be found at a given site. Therefore, I suggest a hierarchical set of actions should be considered, each benefiting birds at different levels of biological organization and spatial scale. Actions to preserve forest area and avoid fast land-use changes should have higher priority. The provisioning of large trees and deadwood would then ensure that the forests retain those structures and functions that support the establishment of bird populations in optimal habitats.
Article
Full-text available
Zelkova abelicea is an endemic tree species growing in several localities in the mountainous regions of Crete, Greece. To date, the microarthropod species associated with this tree species have not been identified. Since Z. abelicea populations are isolated and fragmented, it was hypothesized that the characteristics of microarthropod assemblages, particularly in the case of springtails (Collembola), would vary and differ among localities. Moreover, rare microarthropod species that colonize microhabitats not included in previous studies on Zelkova trees were expected to be recorded. Samples were collected from the bark and twigs of Z. abelicea at eight localities in all main mountain ranges. Among the collected material, Collembola were the most numerous (10,285), followed by Acari (2237) and representatives of Psocoptera (422). The obtained material and statistical analyses showed that the arthropod assemblages differed considerably at each experimental site, with the most distinct assemblage characteristics observed at the Gerakari site on Mt. Kedros in central Crete. The most numerous specimens were species of Collembola: Xenylla maritima (3844), Xenylla sp. 2 (maritima complex) (3364) and Xenylla sp. 1 (maritima complex) (2631). A total of 33 Collembola species were recorded, of which 19 had not been previously reported in Crete. Among them, 11 species were likely new to science and will be the subject of separate taxonomic studies.
Article
Full-text available
La biodiversità forestale può essere monitorata attraverso indicatori come i microhabitat ed il le-gno morto, che costituiscono il substrato fertile per lo sviluppo delle specie saproxiliche. Tra i primi utilizzatori di queste nicchie ecologiche ci sono artropodi, uccelli e piccoli mammiferi, anche se gli insetti, ed in particolare i Coleotteri, sono quelli maggiormente rappresentati. Nel 2020, nei boschi misti di abete bianco e faggio della Riserva di Vallombrosa, è stato avviato uno studio volto ad esaminare i coleotteri saproxilici presenti e le relazioni tra questi e alcuni indicatori di biodiversità forestale. In 47 aree di saggio sono stati monitorati i coleotteri volanti e striscianti ed è stato eseguito il rilievo dei microhabitat, del legno morto e della struttura forestale. In questo lavoro si riportano i primi risultati ottenuti dallo studio. Nei soprassuoli esaminati sono state rinvenute specie incluse nella Lista Rossa dei Coleotteri Saproxilici Italiani e specie tutelate dalla Direttiva Habitat. Sono stati censiti 2573 microhabitat che presentano relazioni ecologiche con i coleotteri campionati. Il rapporto tra il volume della necromassa e il volume degli alberi vivi è risultato pari al 39%. I risultati sono discussi per descrivere il ruolo ecologico della coleotterofauna rispetto agli indicatori di biodiversità considerati. Parole chiave: microhabitat; legno morto; coleotteri saproxilici; conservazione della biodiversità.
Book
Full-text available
International conventions and resolutions on biological diversity, sustainable forest management and climate change have led in recent decades to an increasing interest in having reference values from forests undisturbed by man. An outstanding example of such an undisturbed forest is the primeval forest of Uholka-Shyrokyi Luh within the Carpathian Biosphere Reserve (Ukraine). It is approximately 9000 ha (90 km2) in area and is thought to be the largest primeval forest of almost pure European beech (Fagus sylvatica L.). In 2010, the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, the Ukrainian National Forestry University UNFU and the Carpathian Biosphere Reserve CBR carried out a sampling inventory of the Uholka-Shyrokyi Luh forest (survey perimeter 10?282 ha) to obtain representative data for the main forest parameters. Given the remoteness of the area, long walking distances and difficult terrain, careful planning and organisation were required, as well as the logistic support of the local forest service. The field work was carried out by six mixed teams of Swiss and Ukrainian students and scientists, guided by three survey leaders from Switzerland and Ukraine. Two teams together shared a leader and a cook, and lived in decentra­lized camps, which were moved every week to minimize the walking needed to reach the sample plots. The collaboration between the Ukrainians and Swiss worked very well and was enriching for both sides. During the two-month sampling period, the teams assessed 314 sample plots laid out on a systematic grid. All living and standing dead trees = 6 cm DBH (diameter at 1.3 m above ground) within the 500 m2 circle plots were measured and assessed for features relevant for biodiversity. Lying deadwood was assessed with line-intersect sampling (3 lines each 15 m long per plot), and small trees (= 10 cm height and < 6 cm DBH) were surveyed on subplots consisting of three concentric circles 5, 10 and 20 m2 in area. The stand structure and any traces of anthropogenic use were assessed on a circular interpretation area of 2500 m2 around the sample plot centre. The primeval forest of Uholka-Shyrokyi Luh shows all the typical features of an old-growth forest shaped by small-scale disturbances. The structure was mainly three-layered, and most of the gaps encountered were not larger than the crown of a canopy tree. The growing stock per ha was 582 (± 14) m3 (mean ± standard error) and the deadwood volume 163 (± 8) m3. The ratio of standing to lying deadwood was 1:?5. The maximum DBH measured was 150 cm, and 10 trees per ha had a DBH of at least 80 cm. The density of habitat trees, i.e. living trees with features such as cracks, holes, bark damage or similar that provide microhabitats, was 150 (± 8) per ha (35?% of the living trees). Of all the trees recorded, 97?% were beech, although 14 other tree species were identified. All species found in the tree population = 6 cm DBH were also present in the regeneration. Traces of human presence were encountered on 19?% of the assessed plots (interpretation areas), mainly in the buffer and regulated protection zone of the protected massif. Most of these traces do not affect the integrity and pristine character of the forest. Nevertheless, they imply a certain pressure exerted from the nearby settlements and from the mountain pastures. The data obtained provide good reference values for old-growth beech forests and a valuable basis for more detailed analyses and comparisons with other old-growth and managed forests. The inventory was carried out and documented in a replicable way, and can thus be repeated if desired. The plots may also be used for other non-destructive studies, e.g. on fungi.
Article
Full-text available
European forest managers are implementing set-aside measures in managed forests to restore key structures for forest biodiversity such as tree-related microhabitats (TreMs). However, the time required to regenerate these structures is little known. We assessed the patterns of thirteen TreM types on 282 plots in 24 lowland forests in southwestern France. We applied a synchronic sequence ranging from 1 to 80 years after the last harvest, a time frame which is considered long enough to observe significant changes in the TreM profile. We sampled lowland beech–oak coppice-with-standards stands representative of the different forest ownerships and management regimes occurring in France; our assessment included both public and private forests with or without formal management plans. We found that both TreM density and diversity just after harvesting were lower, though not significantly so, in private stands without any management plan than in the other management regimes. We observed both significantly higher TreM density and diversity in plots harvested 10–15 years ago than in plots harvested 1–5 years ago. The next marked difference did not occur until stands had been harvested 70–80 years ago. Globally, time since last harvest was the best explanatory variable for variations in both TreM density and diversity. We therefore recommend: (1) conserving more habitat trees in harvested areas, particularly cavity trees, since the densities we observed were much lower than the densities required by cavity-dwelling species, and (2) letting set-aside patches freely complete several full silvigenetic cycles. This latter practice would avoid the inefficacy (or possibly even negative effects) of a temporary conservation network, and would also simplify management of the network over time. Further research should assess TreM occurrences in a permanent reserve network. Diachronic observations would make it possible to highlight the drivers of TreM profile development.
Conference Paper
Full-text available
We present an aerial robotic platform for remote tree cavity inspection, based on a hexacopter Micro-Aerial vehicle (MAV) equipped with a dexterous manipulator. The goal is to make the inspection process safer and more efficient and facilitate data collection about tree cavities, which are important for the conservation of biodiversity in forest ecosystems. This work focuses on two key enabling technologies, namely a vision-based cavity detection system and strategies for high level control of the MAV and manipulator. The results of both simulation and real-world experiments are discussed at the end of the paper and demonstrate the effectiveness of our approach.
Technical Report
Full-text available
Large quantities of deadwood and a high density of old microhabitat-bearing trees are characteristic elements of natural forests, especially of the old-growth phases. These are often absent or rare in managed forests, even in forests under close-to-nature management. Yet, an important share of forest biodiversity is strictly or primarily dependent on such elements for their survival, especially ‘saproxylic’ species, those are species depending on deadwood. Tree related microhabitats are therefore recognised as important substrates and structures for biodiversity in forests. The retention of both existing and future tree microhabitats is thus one important aspect to take in to consideration in forest management. Giving tree microhabitats increased attention will help sustain and increase the habitat value for biodiversity also in managed forests . This reference field list is developed to support training exercises conducted in Integrate+ Marteloscope sites. It aims at supporting forest managers, inventory personnel and other groups in identifying and describing tree microhabitats in the course of such exercises. It can also find use as illustrative material in forest education and as background documentation for other training events and field excursions.
Book
Full-text available
Traditionally the purpose of National Forest Inventories (NFIs) has been to provide continuously updated information regarding the state of a given nation's forest resources, including their timber volumes, species composition and sustainable development. But with increased international reporting requirements - to the FAO, the ITTO, the UN's Framework Convention on Climate Change, the Ministerial Conference Protecting Forest in Europe and other international bodies - the potential role of how NFIs can accurately respond to these requirements has received some considerable attention. Addressing the issue of how well countries are able to respond to current international reporting requirements, this book discusses the importance of comparable reporting, and the possible approaches for achieving comparability across Europe and globally. It includes country status reports from 37 countries, worldwide, and it discusses methodologies and techniques for a common reporting system. With its collection of inventories and detailed discussions on the current status and future needs of NFIs, this book provides an invaluable resource for anyone involved in developing, managing, monitoring or contributing to forest inventories, as well as to those who are researching or practising forest resource management.
Article
Full-text available
Context Hoverflies are often used as bio-indicators for ecosystem conservation, but only few studies have actually investigated the key factors explaining their richness in woodlands. Objectives In a fragmented landscape in southwest France, we investigated the joint effects of woodland area, structural heterogeneity, connectivity and history on the species richness of forest-specialist hoverflies, and whether there was a time lag in the response of hoverflies to habitat changes, and tested the effect of spatiotemporal changes. Methods Current species richness was sampled in 48 woodlands using 99 Malaise traps. Structural variables were derived from a rapid habitat assessment protocol. Old maps and aerial photographs were used to extract past and present spatial patterns of the woodlands since 1850. Relationships between species richness and explanatory variables were explored using generalized linear models. Results We show that current habitat area, connectivity, historical continuity and the average density of tree-microhabitats explained 35 % of variation in species richness. Species richness was affected differently by changes in patch area between 1979 and 2010, depending on woodland connectivity. In isolated woodlands, extinction debt and colonization credit were revealed, showing that even several decades are not sufficient for hoverflies to adapt to landscape-scale habitat conditions. Conclusions These findings emphasise the importance of maintaining connectedness between woodlands, which facilitates the dispersion in a changing landscape. Our results also highlight the benefits of using a change-oriented approach to explain the current distribution patterns of species, especially when several spatial processes act jointly.
Article
Full-text available
Beech forests previously covered substantial areas of the continental region of Europe, however, their current distribution is limited to a small percentage of their former yet still potential range. Many beech forests are now protected under the European Union-wide conservation approach of Natura 2000. We analyse the impact of Natura 2000 on the management of beech forests via social science data on management practices gathered from 73 interviews with local stakeholders within nine case study sites in Austria, France, and Germany, and via an ecological analysis of Natura 2000 management plans (MPs). Our data reveals that the Natura 2000 implementation has had little impact on forest management practices. We found that the Natura 2000 network is well known amongst stakeholders, yet the objectives and measures for beech forest protection are usually vaguely defined in the MPs. According to our interviewees, in many cases this vagueness results in a disregard for the MPs, which hence fail to guide the management of the forests protected under Natura 2000. In addition, when ecological thresholds are included in the MPs, they are often below recommendations based on conservation research. In the case of the structural bio-indicator deadwood, the thresholds given by MPs for a favourable site conservation status were significantly lower than those considered within conservation science to be necessary in order to conserve typical beech forest biodiversity. We conclude that while Natura 2000 has raised awareness of the importance of European beech forests for biodiversity conservation, it needs significant additional efforts to make it an effective policy for forest biodiversity conservation.
Thesis
Full-text available
The Violet Click Beetles - Limoniscus violaceus (Müller, 1821) – is a coleopteran species living within wood mould of hollow trees. Endangered in Europe, it is included in Annex II of the “Habitats” directive that aims to ensure the preservation of habitats and species of Community interest throug the Natura 2000 network. Managers of this kind of area must consequently guarantee the favorable conservation status of the species. However, difficulties for detecting the species have limited the accumulation of knowledge about its biology and its ecology. This weakness has motivated this doctoral thesis. First, all data relative to the species’ distribution are compiled. 184 localities in 17 countries are given. Several discordances with Natura 2000 data are highlighted. A survey method using emergence traps is developed and tested in 5 French Natura 2000 areas. A predictive model of the presence of Limoniscus violaceus based on two factors easy to handle (the degree of hollowing of the cavity and the circumference at 30 cm height) is identified. The study of these factors’ thresholds and their confidence intervals leads to a decision rule for the assessment of habitats favorable to Limoniscus violaceus. Meanwhile, analysis of the composition of assemblages of species sampled result to the determination of 231 saproxylic beetles. Preservation of cavities favorable for Limoniscus violaceus appears beneficial for the majority of them, justifying it potentially being an umbrella species. For further prospection, a list of indicator species is identified. It helps to prioritize areas where monitoring of hollow trees and Limoniscus violaceus should be considered. Study of the dispersal from results of emergence traps crossed with bibliographic knowledge suggests that average population size is around 10 adults with 3 individuals dispersing per cavity each year. Sex-Ratio analysis gives complementary information about the functioning of the species populations. Finally, a case study of conservation strategy in the Forest of Grésigne is presented. To ensure the recruitment of trees that will guarantee the long term persistence of the species, management guidelines are given, based on the current forest management plan and on the results of a study on the origin of cavities.
Article
Full-text available
Process-orientated, unmanaged forest remnants are not sufficient for halting the loss of forest biodiversity. Thus, integrated biodiversity-promoting management for forest inhabitants is needed. Microhabitats, such as tree cavities or bark pockets, are essential for the preservation of saproxylic species and of critical importance for endangered ones. This study investigates (1) which factors trigger the formation of microhabitats at both the individual tree and aggregated plot level, and (2) whether the co-occurrence of microhabitats differs between managed (=logged) and unmanaged forests. Relationships between the occurrence of 17 microhabitat types and individual tree features (e.g. light availability, and tree vitality) and plot characteristics (e.g. stand density index and stand age) in 398 plots dominated by Fagus sylvatica or Pseudotsuga menziesii in Germany and the USA were studied using random-effects logistic and normal regression modelling. Separate analyses were performed for German beech forests, German Douglas-fir forests, and the US Douglas-fir forests. Our results show that (1) tree diameter in breast height (DBH), tree vitality and branchiness or epicormic branches are highly related with the occurrence of one or more microhabitats on individual trees in managed and unmanaged beech and US Douglas-fir forests. In managed German Douglas-fir forests, vitality is not a predictor for the occurrence of microhabitats on a tree, but tree density and the maximum age of trees in a stand in addition to DBH and branchiness have an effect. Time since last management is not a statistically significant predictor for the presence of microhabitats at the tree level, but it is for German beech at the plot level. In Douglas-fir-dominated forests both in Germany and in the USA, the stand density index was the only common predictor at the plot level. (2) Unmanaged German beech and Douglas-fir forests exhibit more statistically significant and positive correlations with microhabitat groups than managed stands, implying that the presence of one microhabitat group on a tree is associated with the presence of other microhabitat groups. We finally conclude that measures for supporting microhabitat inhabitants in managed forests are scale and species dependent (tree versus plot level; beech versus Douglas-fir-dominated forests). Trees that carry microhabitats seem to have similar features independently of forest management. At the plot level, density management may trigger the accumulation of microhabitats. Our results indicate that in forest management, it is possible to consider the factors influencing the formation of microhabitats and implement adequate forest practices to advance their formation.
Article
Full-text available
Mycena juniperina Aronsen was collected in March 2013 in the Origano-Brachypodietum association from trunks of living Juniperus communis in the Pieniny Mts (S Poland). The species is described and illustrated based on Polish specimens, its ecology and general distribution are outlined, and it is compared with similar species: M. meliigena (Berk. & Cooke) Sacc., M. pseudocorticola Kühner, and others.
Book
Full-text available
Management goals and ecosystem functions such as biodiversity conservation can be met in both set-aside forest reserves and off-reserve forests. The major argument for well developed and protected forest reserves is the increase of alpha-diversity with extended succession periods and turn-over cycles. However, the establishment of new protected areas is limited due to space and competing management goals. Trade-offs have to be made where such conflicts of interest occur. Accordingly, emphasis is shifted towards integrating rare forest biotopes and structural attributes into production forests. Forests in Central Europe are often managed on the basis of silvicultural principles with high forest management standards. Integrative forest management aims to maximize the cross-section between the different main functions of modern forestry: production, protection and conservation. The area of synergy, however, is limited and a certain amount of exclusive area is needed to guarantee different ecosystem functions. The present volume contains a compilation of the results of the research project Integrate. Based on the contributions from more than seventy renowned scientists in this field, Integrate has attempted to make available the most recent knowledge and the best international scientific expertise on the complex relationships, trade-offs and emerging challenges regarding the integration of forest biodiversity conservation into forest management.
Article
Full-text available
The formation and persistence of tree cavities are key ecological processes that influence the abundance, diversity, and conservation of cavity - nesting and cavity - roosting vertebrates in forests and savannas worldwide (von Haartman 1957; Lindenmayer et al. 1990; Evelyn and ...
Article
Full-text available
Polypore inhabiting beetles in the Moscow region were studied. Sixty-one polypore species harboured 261 species of beetles (174 species coming to polypores as imago, 87 species developing in polypores at larval stage). The highest number of species was found in polypores growing on deciduous trees: Fomes fomentarius (102 beetle species), Polyporus squamosus (94 species), Laetiporus sulphureus (81 species) and Piptoporus betulinus (62 species). Imaginal species diversity is much higher than larval, although the later can be more abundant. Ennearthron cornutum (found on 20 species of polypores) and Cis comptus (16 species) occurred in the largest number of fungal species.
Article
Full-text available
Through physical state changes in biotic or abiotic materials, ecosystem engineers modulate resource availability to other organisms and are major drivers of evolutionary and ecological dynamics. Understanding whether and how ecosystem engineers are interchangeable for resource users in different habitats is a largely neglected topic in ecosystem engineering research that can improve our understanding of the structure of communities. We addressed this issue in a cavity-nest web (1999-2011). In aspen groves, the presence of mountain bluebird (Sialia currucoides) and tree swallow (Tachycineta bicolour) nests was positively related to the density of cavities supplied by northern flickers (Colaptes auratus), which provided the most abundant cavities (1.61 cavities/ha). Flickers in aspen groves provided numerous nesting cavities to bluebirds (66%) and swallows (46%), despite previous research showing that flicker cavities are avoided by swallows. In continuous mixed forests, however, the presence of nesting swallows was mainly related to cavity density of red-naped sapsuckers (Sphyrapicus nuchalis), which provided the most abundant cavities (0.52 cavities/ha), and to cavity density of hairy woodpeckers (Picoides villosus), which provided few (0.14 cavities/ha) but high-quality cavities. Overall, sapsuckers and hairy woodpeckers provided 86% of nesting cavities to swallows in continuous forests. In contrast, the presence of nesting bluebirds in continuous forests was associated with the density of cavities supplied by all the ecosystem engineers. These results suggest that (i) habitat type may mediate the associations between ecosystem engineers and resource users, and (ii) different ecosystem engineers may be interchangeable for resource users depending on the quantity and quality of resources that each engineer supplies in each habitat type. We, therefore, urge the incorporation of the variation in the quantity and quality of resources provided by ecosystem engineers across habitats into models that assess community dynamics to improve our understanding of the importance of ecosystem engineers in shaping ecological communities.