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Summary: Partnerships between Indigenous People and governments for joint management of ancestral lands, designated as protected conservation areas for biodiversity and cultural heritage, provide an opportunity to leverage accumulated traditional land management knowledge with emerging science. In Australia, veteran or large old trees in natural landscapes are of significant ecological importance, and among the Indigenous communities, they are living monuments to historical cultural practices, but their survival, endurance and long lives are rarely acknowledged to afford them protection. In sub‐tropical Australia, the lack of consistent annual growth rings in stem wood makes it difficult to estimate the age of large trees using methods such as the periodic diameter increment. Ngugi et al., 2020 published radiocarbon (14C) dates using wood core ('pith‐wood') samples from 12 Indigenous culturally‐significant trees covering five species on Minjerribah (North Stradbroke Island). Due to the imprecise calendar age results of the single samples used in the original study (Ngugi et al., 2020), subsequent radiocarbon dating of an additional three wood core samples from each tree was undertaken to age the trees more precisely. The revised tree ages ranged from 63 to 531 years and suggest an important role of past Indigenous land management practices into protecting Bugari (Cypress Pine, Callitris columellaris F. Muell.) from deadly crown scorching fires. These results underscore the importance of incorporating Indigenous practices in current fire management strategies and plans. Estimating tree ages based on the periodic diameter increment method overestimated the age relative to that derived from radiocarbon dating. New bias correction factors were developed for adjusting the recorded periodic tree diameter increments. [ABSTRACT FROM AUTHOR]

In forests, the amount and diversity of structural features with high value for biodiversity, such as large trees and dead wood, are affected by productivity, stand age, and forest management. For efficient conservation of forest biodiversity, it is essential to understand the combined effects of these drivers. We used data from the Swedish National Forest Inventory to study the combined effects of productivity, stand age, and management for wood production on structures with high value for biodiversity: tree species richness, large living trees, dead wood volume, and specific dead wood types. Forest management changed the relationship between productivity and amount or diversity of some of the structures. Most structures increased with productivity and stand age, but decreased due to management. The negative effect of management was greatest for structures occurring mainly in high-productivity forests, such as deciduous dead wood. Thus, biodiversity conservation should target high-productivity forests to preserve these structures. [ABSTRACT FROM AUTHOR]

Integrating the conservation of biodiversity into silvicultural practices is one of the main challenges facing forest owners in the promotion of an emergent approach to sustainable forest management across European forests. The Mediterranean forests are among the richest biodiverse forest ecosystems due to their environmental heterogeneity, but climate change is threatening their integrity, with critical implications for the availability of ecosystem services. Forests managed for commercial purposes are under increasing pressure to provide timber while supporting biodiversity. This study aims to analyse the relationship between tree-related microhabitats (TreMs), which are structures occurring on living or standing dead trees that constitute an essential substrate for several living species, and beetles, an important indicator species group for forest biodiversity monitoring. Four generalized linear models were fitted to assess the influence of environmental factors, forest structure, and biodiversity-related parameters on the abundance and richness of beetles, mainly on saproxylic beetles. The study highlights significant associations between the abundance and richness of individual groups and types of TreMs and the Italian Red List of saproxylic species. Therefore, TreMs can serve as a tool to map, monitor, and enhance forest biodiversity in managed forests. [ABSTRACT FROM AUTHOR]

The habitat trees and their microhabitats are considered to be key features for forest-species and are often employed to measure the biodiversity and naturalness of a forest. At the tree scale, the most common factors that favour microhabitats occurrence are the tree species, diameter at breast height (dbh), status (i.e. living vs standing dead), the age of the trees and the forest management (in managed forests). To provide additional information to enable better prediction of the occurrence of particular microhabitats can be considered at plot level: slope, exposure, altitude and presence of cliffs. In the forest district Bârzava in the research plot it were identified 85 habitat trees: 51 sessile oak trees, 33 beech trees and one hornbeam tree. The most diverse microhabitats were observed in the sessile oak species (36) compared to the beech species (24) - thus it can be seen that the tree species is an important factor favouring the appearance of microhabitats. The importance of habitat trees and their microhabitats for forest biodiversity as well as their ecological services, are becoming increasingly valued by society and protecting them is of utmost importance. [ABSTRACT FROM AUTHOR]

Abstract Background Tree-related microhabitats (hereafter, “TreMs”) are key components of forest biodiversity but they are still poorly known in North American hardwood forests. The spatial patterns of living trees bearing TreMs (hereafter, “TreM-trees”) also remain to be determined. As logging practices can lead to a loss of TreM-trees and of their associated biodiversity, it is essential to identify the factors explaining TreM occurrence to better integrate them into forest management. We therefore inventoried TreMs in 4 0.5-ha survey strips in northern hardwood forests in Quebec, Canada, while recording the spatial location of each tree. Two strips were located in unmanaged old-growth forests, and 2 were in forests managed under selection cutting. All 4 stands were dominated by sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrn.). Beech bark disease, an exotic pathology, was observed in all the strips. Results Large diameter at breast height and low tree vigor were the main characteristics explaining the presence of TreMs at the tree scale. TreM-trees presented slight spatial aggregation patterns. These aggregates, however, were not well-defined and were generally constituted by a large number of trees bearing few different types of TreMs. Two TreM classes (broken branch or top and woodpecker lodge) also presented a spatial aggregation. Logging practices had no significant effect on TreM occurrence. Beech bark disease increased the frequency of senescent beeches. The impact of this pathology on TreMs was however mitigated by the small size of infected trees and probably by the short time elapsed since its appearance. Conclusion The factors explaining the presence and abundance of TreMs on trees has so far been little studied in North American hardwood forests. Our results highlight that TreM-tree characteristics in the surveyed forests are consistent with those of previous studies conducted in other forest types and regions (e.g., Europe or Northwestern America). To our knowledge, this study is also the first to identify a spatial aggregation of TreM-trees and of specific TreM classes. It will be nevertheless necessary to determine whether the small impact of logging activities we observed results from current or past management practices.

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 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. [ABSTRACT FROM AUTHOR]

Background: Tree-related microhabitats (hereafter, "TreMs") are key components of forest biodiversity but they are still poorly known in North American hardwood forests. The spatial patterns of living trees bearing TreMs (hereafter, "TreM-trees") also remain to be determined. As logging practices can lead to a loss of TreM-trees and of their associated biodiversity, it is essential to identify the factors explaining TreM occurrence to better integrate them into forest management. We therefore inventoried TreMs in 4 0.5-ha survey strips in northern hardwood forests in Quebec, Canada, while recording the spatial location of each tree. Two strips were located in unmanaged old-growth forests, and 2 were in forests managed under selection cutting. All 4 stands were dominated by sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrn.). Beech bark disease, an exotic pathology, was observed in all the strips. Results: Large diameter at breast height and low tree vigor were the main characteristics explaining the presence of TreMs at the tree scale. TreM-trees presented slight spatial aggregation patterns. These aggregates, however, were not well-defined and were generally constituted by a large number of trees bearing few different types of TreMs. Two TreM classes (broken branch or top and woodpecker lodge) also presented a spatial aggregation. Logging practices had no significant effect on TreM occurrence. Beech bark disease increased the frequency of senescent beeches. The impact of this pathology on TreMs was however mitigated by the small size of infected trees and probably by the short time elapsed since its appearance. Conclusion: The factors explaining the presence and abundance of TreMs on trees has so far been little studied in North American hardwood forests. Our results highlight that TreM-tree characteristics in the surveyed forests are consistent with those of previous studies conducted in other forest types and regions (e.g., Europe or Northwestern America). To our knowledge, this study is also the first to identify a spatial aggregation of TreM-trees and of specific TreM classes. It will be nevertheless necessary to determine whether the small impact of logging activities we observed results from current or past management practices. [ABSTRACT FROM AUTHOR]

Integrating nature conservation effectively in forests managed for timber production implies reconciling a trade-off between ecological and economic objectives. In continuous cover forest management, this culminates in decisions about tree harvesting (or retention) determining both the prevalence of tree-related microhabitats in the forest and the economic viability of timber management. Applying an innovative mixed methods approach, we compare conservationists and foresters performing a tree selection exercise. We assess the outcomes of their forest management decisions quantitatively and explore their strategies and the underlying reasoning based on qualitative data. Our findings show that particularly the habitat trees differ greatly between the two groups: while conservationists retained almost exclusively large oaks at often high opportunity costs, foresters retained a notable number of smaller-diameter hornbeams. These differences are related to a different perception of opportunity costs of retention by both groups, as well as because they do not agree about how to value current tree-related microhabitats and their projection into the future. Such diverging patterns of reasoning imply incompatible interpretations of what constitutes a habitat tree. Our results indicate that it is important to apply benchmarks for evaluating ecological goals as well as to increase foresters' and conservationists' understanding about the motivations and restrictions of the respective counterpart. Our study points out a significant potential for (mutual) learning, and illustrates the complementarity of quantitative and qualitative research methods to examine tree selection behaviour. [ABSTRACT FROM AUTHOR]

Summary: Appropriate fire management strategies are needed to protect forests and large old ecologically and culturally significant trees in natural landscapes. The aim of this study was to determine the age of large old and relic trees of cultural significance that included Cypress Pine (Callitris columellaris F. Muell.), a species that is sensitive to crown scorching fires in a fire‐prone landscape, and to calibrate a tree‐growth‐rate method for estimating tree age. Twelve large trees were dated using radiocarbon (14C) dating. The trees are located on North Stradbroke Island (Indigenous name: Minjerribah), southeast Queensland (Australia) in a fire‐prone landscape where recent wildfires have destroyed many large trees. The median tree ages ranged from 155 to 369 years. These results suggest an important role of past Indigenous land management practices in protecting Cypress Pine from crown scorching fires. The tree‐growth‐rate‐based method for estimating tree age generally overestimated the age derived from radiocarbon dating. Bias correction factors were developed for correcting various measures of periodic growth rates. This study provides evidence that appropriate low‐intensity fire strategies have the potential to contribute to the survival of forests and conserve large old trees. [ABSTRACT FROM AUTHOR]

Foresters in Poland have accepted the presence of coarse woody debris (CWD) in managed forests, but there is still a tendency to remove any diseased tree from the forest stand as soon as possible. Trees invaded by bark beetles or infested by pathogenic fungi are considered a threat to forest health. That approach is typical for timber-oriented forest management. In Poland, where multifunctional forestry is a declared policy in all forests belonging to the National Forests Enterprise, the rules for managing and protecting forest stands are uniform throughout the country. This does not allow some diseased or malformed specimens to be spared during forestry work as prospective habitat trees and as future sources of CWD. Without relaxation of the rules concerning sanitary cutting, it will be difficult to maintain or increase the current amount of CWD. There is no point in sparing diseased or injured trees in forest areas that are of no great value for recreation or conservation, where timber production is the priority, but in areas where recreation and conservation of biodiversity are of high value the rules should be changed to allow the number of habitat trees and the amount of CWD to increase. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Oak forests are of great economic and conservation importance. • We identify integrative management options for forestry and nature conservation. • Light availability is a strong link between forestry and conservation demands. • There is an urgent need for integrative oak forest planning approaches. • Ecological continuity should be secured in structural "sustainability units". Abstract Central European temperate oak woodlands are highly valued for their rich biodiversity. They are also of great economic importance and forest management aims to produce high quality timber, which demands high investments. The aim of this literature review is to identify management options for forestry and nature conservation that sustain both the ecological value of oak forests and the economic viability of oak silviculture. We addressed three main questions: (a) Oaks and close-to-nature forestry – what are the key silvicultural challenges and options?, (b) What is the particular significance of ecological continuity and which structural features are of importance for biodiversity conservation in oak forests?, (c) What are the key elements and possible strategies of forest management that sustain the ecological values in oak forests in combination with viable forestry? Light availability appeared to be a conspicuous link connecting the conservation and the silvicultural aspects of multifunctional oak forest management: Both young oak trees and multiple oak woodland specialist species are characterized by their need for increased sunlight exposure. This common denominator provides a sound basis for integrative management practices for forestry and nature conservation. The concept of retention forestry offers purposeful approaches. So the harvest of valuable timber oaks or the creation of canopy gaps for oak regeneration can be used to release the crowns and trunks of habitat oaks from shading and competition. When looking at the management of oak woodland biodiversity hotspots, the re-establishment of (modified) historical forest management techniques, which increase stand openness and create transitional habitats that provide suitable oak regeneration niches, seems to be necessary. Not only the continuity of oak woodland cover and natural site conditions, but also the uninterrupted temporal continuity and availability of wood-related structural features turned out to be of particular importance for oak woodland specialist species. We identified an urgent need for systematic forest planning approaches that secure the long-term availability of these structural features within areas or "sustainability units" that are large enough to maintain viable populations of oak woodland specialist species. In particular, conservation-oriented forestry measures should mainly be implemented in those areas, where the greatest effectiveness is to be expected. In the sustainability units, oak regeneration measures ought to take place either in close vicinity to old oak stands or directly in these stands. The choice of one of these options should be based on a careful consideration of the needs and possibilities of both silvicultural and nature conservation management. [ABSTRACT FROM AUTHOR]

In the last few years, the occurrence and abundance of tree-related microhabitats and habitat trees have gained great attention across Europe as indicators of forest biodiversity. Nevertheless, observing microhabitats in the field requires time and well-trained staff. For this reason, new efficient semiautomatic systems for their identification and mapping on a large scale are necessary. This study aims at predicting microhabitats in a mixed and multi-layered Mediterranean forest using Airborne Laser Scanning data through the implementation of a Machine Learning algorithm. The study focuses on the identification of LiDAR metrics useful for detecting microhabitats according to the recent hierarchical classification system for Tree-related Microhabitats, from single microhabitats to the habitat trees. The results demonstrate that Airborne Laser Scanning point clouds support the prediction of microhabitat abundance. Better prediction capabilities were obtained at a higher hierarchical level and for some of the single microhabitats, such as epiphytic bryophytes, root buttress cavities, and branch holes. Metrics concerned with tree height distribution and crown density are the most important predictors of microhabitats in a multi-layered forest.

Highlights • Regrowth forest is important biodiversity habitat when little mature forest remains. • Identifying regrowth with mature forest elements can guide strategic reservation. • Stand maturity related weakly to remote-sensed and measured environmental variables. • Eucalypt crown senescence weakly indicates stands likely to contain habitat trees. • Timber production and conservation are not in conflict on more productive sites. Abstract In this study, we examined the associations between field-assessed floristic and structural habitat values for mature forest and GIS-derived variables to assess whether high conservation value forests could be predicted for strategic reservation at a landscape scale. We investigated the Eucalyptus regnans forests of the Victorian Central Highlands in south-eastern Australia, where several extensive wildfires in the last century have left little mature forest. We assessed the extent to which the floristic composition and a suite of habitat-related structural variables could be explained by two forest inventory GIS variables (percentage senescence and site productivity) and whether explanatory capacity improved from inclusion of additional environmental variables (climate, soils, topography, structure and spatial location). Results showed that the floristic composition was weakly related to productivity, but not to percentage senescence. Four habitat-related structural variables were positively related to percentage senescence (density of old-growth eucalypts, the quadratic mean diameter (QMD) of both live and dead eucalypts, and the maximum eucalypt form class (a proxy for tree hollows)) while the volume of CWD had a marginally significant positive relationship. Three structural variables were related to productivity (the maximum eucalypt form class, the QMD of dead understorey trees and of dead eucalypts). However, in all cases the explanatory power of percentage senescence and productivity was weak (proportion of deviance explained by the models <0.3). Inclusion of the other environmental variables did not substantially improve explanatory power in any case. Our results suggest that there is a high degree of stochasticity driving floristic and structural composition within these forests, making the detection of most mature forest values difficult without site visits. There may be some limited capacity for the presence of senescent trees visible in aerial photographs to highlight stands more likely to contain habitat trees, but there was no relationship with floristic maturity. Our results also suggest that more productive sites do not have substantially greater habitat values, indicating that the current timber harvesting approach of prioritising the harvest of stands on more productive sites is unlikely to have negative consequences for biodiversity. [ABSTRACT FROM AUTHOR]

Hollow-using fauna are thought to be particularly vulnerable to timber harvesting, and habitat for these species is often managed by retaining single hollow-bearing trees or patches of hollow-bearing trees within the harvested area. This study examined tree retention, survival and use by arboreal mammals in 27 small clumps of trees (0.04–0.21 ha) retained at ten partial harvest sites and 24 clumps of trees in nearby unharvested sites in Tasmania, Australia. Harvested sites were assessed on three occasions (1999, 2005–06 and 2014) and unharvested sites on two occasions (2005–06 and 2014). Of the retained clumps in harvested areas, 96% contained at least two habitat trees at the time of first survey (one year after harvest) which is the minimum required under the Tasmanian Forest Practices Code. Loss of retained trees in clumps between 2005–06 and 2014 was higher in harvested sites (average of 11.7% of all trees and 1.5% of habitat trees per clump) than unharvested sites (average of 2.8% of all trees and 0.3% of habitat trees per clump), but was comparable to or lower than rates of loss in many other studies. Trees were more likely to fall if they were dead and had little burn damage at the time of last survey. Factors found to influence tree death included the interaction between burn damage and the size of the tree, with the likelihood of a heavily burnt, average sized tree dying being twice that of an unburnt tree. Scratch marks from arboreal mammals were more prevalent in large trees with visible hollows, particularly in the clumps in harvested areas. In conclusion, the Tasmanian Forest Practices Code provisions were generally implemented as required and the evidence suggests the retained clumps of trees survive and are effective to some degree at providing habitat and promoting recolonisation by fauna in partial harvest coupes. However, further work is required to assess the adequacy of the clump provisions, when combined with management for other values in production forests, for maintaining hollow-using fauna throughout their range. [ABSTRACT FROM AUTHOR]

Riparian forests are considered as complex and biologically rich habitats. They play a crucial role for biodiversity conservation, in particular in landscapes under strong management pressure. Tree-related microhabitats (TreMs) support a wide array of biodiversity and some authors have suggested using them as indirect biodiversity indicators in forest ecosystems. This study investigates TreM profiles of a temperate riparian forest as last natural forest ecosystem in a context of intensively managed landscape along the Ciron river and of surrounding pine plantations of the Landes de Gascogne forest (France) and explores their drivers at tree and plot scales. A total of 28 transects perpendicular to the river, representing 84 0.1 ha-plots, were selected along the Ciron river and three of its tributaries. At tree scale, diameter at breast height (dbh), tree species and tree status (living, standing or lying dead) were significant predictors of TreM diversity. At plot scale, Alnus glutinosa was found to significantly contribute to riparian forest TreM profiles by hosting specific TreMs. The same role was highlighted for broadleaved species in pine plantations. At plot scale, the drivers of TreM diversity varied depending on plot location in the transect (riparian forest, plantation forest, intermediate area). We found that the presence of lying dead trees is an important driver of TreM diversity at plot scale, particularly in plantation stand and we thus suggest lying dead trees be included in future studies focusing on TreMs. The rich TreM profile of riparian forests highlights their crucial role in biodiversity conservation. [ABSTRACT FROM AUTHOR]

The general importance of dead wood in European beech forests for species requiring high amounts of decayed wood of large diameter has recently been demonstrated using a functional approach. However, the effect of veteran trees, particularly of living hollow trees with mould, on functional diversity, is less understood. These trees are known to be a habitat for a few endangered and specialized arthropods and epiphytes. Their ecological role as a complex habitat has been assumed, but not yet formally tested. We compared the richness and functional and phylogenetic diversity of saproxylic beetle assemblages of vital beech trees, habitat trees (i.e. trees with partial bark loss, broken crowns or sporocarps) and hollow trees with mould. As expected, the richness of red-listed species increased from vital trees to habitat trees to hollow trees. When we controlled for species richness using null models, both functional and phylogenetic diversity were higher for hollow trees than for habitat trees, which can be explained by the habitat heterogeneity hypothesis. Single-trait analyses revealed that hollow trees promoted species requiring late decay stages, large diameters and shady habitats. This suggests that in beech forests, hollow trees not only promote the few specialists of hollow trees, but also play a superior role for species under pressure by current logging practices and as a keystone structure with high habitat diversity at one tree. We therefore urge forest managers and conservationists to monitor particularly the easy-to-identify hollow trees and the conspicuous species living in such trees, as useful umbrellas for a high-diversity dead-wood habitat. [ABSTRACT FROM AUTHOR]

• Plot context primarily explains tree-related microhabitats occurrence. • Plot context is a black box combining environmental, management and biotic factors. • From the literature, we identified 21 factors that may play a key role in TreM formation. • A sub-set of 9 factors that should be prioritised in the future is suggested. 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. [ABSTRACT FROM AUTHOR]

Highlights: [•] Key saproxylic features derived from rapid habitat assessment to monitor biodiversity. [•] Snags, tree microhabitats and openness are key features for saproxylic beetles. [•] No robust structural biodiversity indicator in deciduous or coniferous temperate forests. [•] Deadwood and microhabitats effects are affected by meso/micro-climatic features. [Copyright &y& Elsevier]

Abstract: The distribution of hollow-using fauna is frequently related to forest type. If hollow occurrence varies with forest type, the use of generic prescriptions for managing the hollow resource may be inappropriate. This study examined the relationship between the occurrence and abundance of tree hollows and site and tree attributes in wet and dry Eucalyptus obliqua forest in Tasmania, Australia. A total of 388 trees at 39 sites were examined before and after being felled. Evidence of invertebrate damage contributing to hollow formation was more common in wet forest than either dry or damp forest. Evidence of hollow formation by fire and fungi was more prevalent in drier than wetter forest. There was no difference among forest types in the proportion of hollows showing evidence of limb breakage. Examination of the site and tree factors related to hollow presence and abundance was done using Classification Trees, Random Forests and generalised linear models. The variables found to be most practical for predicting hollow occurrence were the number of hollows observed before the tree was felled, tree diameter and the amount of dead wood in the canopy. Tree age, an important variable to consider when planning harvest rotations, was strongly associated with hollow presence but had less bearing on hollow abundance. The size of hollows that were found in a tree was related to greater senescence. Although significantly more hollows of all sizes were found in wet forest than either dry or damp forest, the age at which trees began to produce hollows was similar among the different forest types. The models predicted that trees needed to be at least 100 years old before they are likely to contain a hollow and that medium-sized hollows rarely occur in trees younger than 140 years old. Trees grow slightly more slowly in dry forest than wet which means that smaller diameter trees were found to contain hollows in dry forest than wet and that even the largest trees may not contain large hollows in wet forest. Despite this, no differentiation between the forest types was found in the predictive models. It is recommended that trees retained for faunal habitat be at least 100cm in diameter. [Copyright &y& Elsevier]

Abstract: Living trees (green trees) are intentionally retained on logged sites for many purposes such as wildlife conservation, future wood potential and aesthetics. Minimizing the risk that these trees collapse in the short-term will improve the chances that green-tree retention meets its objectives. In a retrospective case-control study, we identified factors significantly associated with the collapse of living trees retained on logged and slash-burnt sites in south-eastern Australia within 8 years of harvesting. Trees with incomplete crowns or trees with at least one visible cavity were, on average, at three times greater risk of collapse relative to trees with complete crowns or no visible cavities, respectively. Trees with fire-scarring, trees retained greater than 50m from intact forest or trees retained in isolation were, on average, around twice the risk of collapse relative to trees without fire-scarring, trees retained within 50m of intact forest or trees retained among other trees, respectively. When considered jointly, the significant factors in a model predicting the collapse of retained trees – tree height, tree diameter, crown form – were all associated with the health of trees. Choosing the healthiest trees possible for fulfilling their function, protecting trees from damage (e.g. fire) and retaining trees near, or among, other trees are likely to reduce the risk of collapse among retained trees and thus contribute to the effectiveness of green-tree retention in logged eucalypt forests. [Copyright &y& Elsevier]

• Quantitative data on development rates of tree microhabitats (TM) are scarce. • Published rates of development of five common TM reviewed. • TM supply formed by initiating events, tree response, and environmental modifiers. • Tree age and growth rate interact in TM dynamics. • Long-term strategy for TM conservation outlined. Many tree-dwelling species inhabit microhabitats that develop slowly in diseased or injured trees. Conservation planning would benefit from explicit knowledge of these processes, notably for resolving conflicts with timber production, arboricultural or public safety goals. We reviewed published rates of development of five selected common tree microhabitats and the factors affecting those rates in living trees. Most of the 71 relevant studies found globally focused on tree-cavities and exposed wood, while the development of witches' broom, bark pocket and dendrotelm microhabitats remains poorly described. Three time parameters emerge as central: minimum tree age; rate of formation; and persistence time of the microhabitat. Among the studied microhabitats, large side cavities are formed in the oldest trees, seldom hosting large vertebrates in trees <100 years old. In contrast, the development of exposed wood, bark pockets and dendrotelms can be compatible with some approaches of even-aged production forestry. The evidence indicates that tree growth rate is a key effect modifier of microhabitat development, which supports short-term wound occlusion but can also expose the tree to chronic disease and decay. For example, side cavities usually develop more rapidly in fast-growing trees, but persist longer in slow-growing trees. Environmental exposure regulates microhabitat development by affecting these growth and degradation responses and pathogen performance, but typical ranges of natural variation in microhabitat development rates can also be distinguished. To mitigate conservation conflicts with production forestry and the management of human environments, microhabitat prone trees should be considered across multiple management cycles, notably to sustain large side-cavities and witches' brooms. We outline retention forestry approaches, reduction of salvage logging, and veteran tree management in the countryside and urban environments as the key arenas of action. Given the high variation in tree microhabitat development, a successful strategy would combine fine-scale retention of existing microhabitats and landscape-scale prediction and planning for future microhabitat formation. [ABSTRACT FROM AUTHOR]

• Large, old trees with hollows provide important habitat for hollow-using species. • Retention forestry can help retain habitat trees in harvested areas. • Aggregated retention retained more habitat trees than other silvicultural systems. • Aerial and ground-based surveys gave similar estimates of habitat tree abundance. • Helicopter surveys are a rapid, cost-effective approach for post-harvest assessment. Habitat trees (mature live and dead trees with hollows) are a keystone habitat in Australian eucalypt forests where tree hollows typically occur in large, old trees. These trees provide potential habitat for hollow-using birds, bats and arboreal marsupials, including many threatened species. Habitat trees may be felled during forest harvesting and can also be negatively affected by wildfires. Shortages of habitat trees in harvesting landscapes can be a limiting factor for populations of hollow-using vertebrates. Retention forestry systems are expected to retain a greater number of habitat trees within sites than traditional clearcutting silviculture, but there is a need to quantify how the pattern of retention (dispersed trees vs. retained clumps) will affect the numbers and types of trees retained. The method of assessment (ground-based vs. aerial surveys) may influence the estimated numbers of habitat trees. We investigated habitat tree retention at the Warra Silvicultural Systems Trial in Southern Tasmania, Australia. This trial was instrumental in developing alternatives to clearcutting in tall, wet, old-growth eucalypt forests. Our research has two objectives. Objective 1 is to assess the numbers of habitat trees retained in various alternatives to clearcutting by comparing: unlogged control areas, 0.5–1 ha clumps retained within a harvested matrix (aggregated retention), trees scattered throughout the harvested area (dispersed retention), and small ~0.08 ha machinery exclusion zones where trees were retained if they were not of commercial value (clearcutting with understorey islands). Objective 2 is to compare ground-based to aerial, helicopter-based, assessment of large live and dead trees. Although low replication of harvest treatments precluded statistical comparison of silvicultural systems, the results, based on 1,260 trees, were clear. Of the various alternatives to clearcutting, aggregated retention retained the greatest proportion of all classes of habitat trees, primarily because of higher retention targets, but possibly also because of greater survival with reduced wind exposure in aggregates. Substantially fewer habitat trees were retained with dispersed retention, and virtually none with understorey islands in clearcutting. Aerial and ground-based assessment methods provided similar estimates of numbers of trees with visible hollows in aggregates and understorey islands (R2 = 0.95). Choice of method for future studies should consider available resources and objectives, since there were advantages and disadvantages of each approach. In conclusion, aggregated retention was found to be the preferred silvicultural system for retaining habitat trees within sites for hollow-using vertebrates, and helicopter surveys provide a rapid alternative to traditional ground-based assessment. [ABSTRACT FROM AUTHOR]

In the last few years, the occurrence and abundance of tree-related microhabitats and habitat trees have gained great attention across Europe as indicators of forest biodiversity. Nevertheless, observing microhabitats in the field requires time and well-trained staff. For this reason, new efficient semiautomatic systems for their identification and mapping on a large scale are necessary. This study aims at predicting microhabitats in a mixed and multi-layered Mediterranean forest using Airborne Laser Scanning data through the implementation of a Machine Learning algorithm. The study focuses on the identification of LiDAR metrics useful for detecting microhabitats according to the recent hierarchical classification system for Tree-related Microhabitats, from single microhabitats to the habitat trees. The results demonstrate that Airborne Laser Scanning point clouds support the prediction of microhabitat abundance. Better prediction capabilities were obtained at a higher hierarchical level and for some of the single microhabitats, such as epiphytic bryophytes, root buttress cavities, and branch holes. Metrics concerned with tree height distribution and crown density are the most important predictors of microhabitats in a multi-layered forest. [ABSTRACT FROM AUTHOR]