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Factors influencing the rate of formation of tree‐related microhabitats and implications for biodiversity conservation and forest management
Abstract
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.
... living vs standing dead) for driving the occurrence and abundance of TreMs (Winter and Möller, 2008;Michel and Winter, 2009;Vuidot et al., 2011;Regnery et al., 2013b;Larrieu et al., 2014b;Paillet et al., 2018Paillet et al., , 2019Kozák et al., 2018;Asbeck et al., 2019). Notwithstanding the abundance of studies on the topic, to date, predictive models have mainly focused on only two basic tree features, namely dbh and species for living trees (Courbaud et al., 2017;Jahed et al., 2020); in some cases, a qualitative variable was used to separate managed and unmanaged forests (Courbaud et al., 2022). Dbh and treespecies are easy to record, and are also routinely assessed by forest managers for silvicultural and monitoring purposes. ...
... However, the power to predict TreM occurrence with these two tree features alone is often rather low, e.g. about 26 % in beech (Fagus sylvatica)-silver fir (Abies alba) forests . Moreover, Courbaud et al. (2022) have shown that site effects are huge. However, these previous works have not been able to highlight what site features influence the presence and dynamics of TreMs. ...
... To quantify the predictive power of the features shared by most of the datasets, we used an international database which integrates 23 harmonized datasets, comprising 100,855 living trees and 10,354 standing dead trees belonging to 89 tree species (appendix; Table 1SM). For each of the eleven TreM subgroups that were designated by Courbaud et al. (2022), we built a Generalized Linear Mixed Model (GLMM) that described the presence/absence of this TreM group in relation to dbh, tree species, tree status (living/standing dead), plot context, and time since the last harvest (four categories: <20y, 21-50y, 51-100y and >100y). Three two-way interactions -namely dbh with status, dbh with time since last harvest, status with time since last harvest -were also included as fixed effects. ...
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.
... Broadleaved tree species generally accumulate TreMs to a greater extent than coniferous species (Courbaud et al., 2017;Krumm et al., 2020;Larrieu & Cabanettes, 2012;Paillet et al., 2019), and early-successional species tend to differ from mid-and late-successional species. Some types of TreMs, such as bark loss, crown deadwood, and rot holes, occur more often on early-successional species (Courbaud et al., 2022). ...
... The process of felling can cause tree damage and injuries that can lead to increased occurrence of TreMs, such as bark loss, dendrotelms, and resinosis (Larrieu & Cabanettes, 2012;Michel et al., 2011). Most TreM groups have reduced formation rates in managed forests compared with unmanaged forests (Courbaud et al., 2022). Investigating TreM occurrences in forests that have never been managed or have not been managed for a long time provides a significant reference for understanding patterns of TreM development under natural conditions. ...
Protecting structural features, such as tree-related microhabitats (TreMs), is a cost-effective tool crucial for biodiversity conservation applicable to large forested landscapes. While the development of TreMs is influenced by tree diameter, species, and vitality, the relationships between tree age and TreM profile remain poorly understood. Using a tree-ring based approach and a large data set of 8038 trees, we modeled the effects of tree age, diameter, and site characteristics on TreM richness and occurrence across some of the most intact primary temperate forests in Europe, including mixed beech and spruce forests. We observed an overall increase in TreM richness on old and large trees in both forest types. The Occurrence of specific TreM groups was variably related to tree age and diameter, but some TreM groups (e.g., epiphytes) had a stronger positive relationship with tree species and elevation. While many TreM groups were positively associated with tree age and diameter, only 2 TreM groups in spruce stands reacted exclusively to tree age (insect galleries and exposed sapwood) without responding to diameter. Thus, the retention of trees for conservation purposes based on tree diameter appears to be a generally feasible approach with rather low risk of underrepresentation of TreMs. Because greater tree age and diameter positively affected TreM development, placing a greater emphasis on conserving large trees and allowing them to reach older ages, for example, through establishment of conservation reserves, would better maintain the continuity of TreM resource and associated biodiversity. However, this approach may be difficult due to the widespread intensification of forest management and global climate change. Article Impact Statement: Conservation of habitat trees based on size, without considering tree age, may impair landscape-level biodiversity potential. This article is protected by copyright. All rights reserved.
... 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). ...
... While strong thinnings promote the growth of light and warmth demanding plant species, they have negative impacts on shade-demanding understory plant species and ectomycorrhizal community composition (Buée et al. 2005). Thinning from below, including the removal of suppressed and poorly formed trees, reduces the amount and diversity of tree-microhabitats (Courbaud et al. 2022). Regeneration cuttings, including clearcut, strip cut, shelterwood cut and patch cut systems, are generally more intensive and have therefore a larger impact on biodiversity than thinnings. ...
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.
... Hence, a tree is suitable for the establishment or improvement of a nest cavity when the wood is softened by fungal infection (in particular for smaller birds). This process takes time and thereby favours hollow formation in larger older trees (Courbaud et al., 2022). Although we did not survey retained trees for the occurrence of cavities, it is reasonable to assume a higher prevalence of these structures in retained trees than in the production trees due to their older age and larger size (Larrieu et al., 2014;Courbaud et al., 2022). ...
... This process takes time and thereby favours hollow formation in larger older trees (Courbaud et al., 2022). Although we did not survey retained trees for the occurrence of cavities, it is reasonable to assume a higher prevalence of these structures in retained trees than in the production trees due to their older age and larger size (Larrieu et al., 2014;Courbaud et al., 2022). The average DBH of the retained trees in our study was 34 cm, and close to 10% of all retained trees were larger than 50 cm. ...
Retention forestry involves saving important forest structures for flora and fauna during the final felling of a stand, including dead wood and variable amounts of living trees, i.e. green tree retention (GTR). Here we evaluate the long-term effects on avian diversity from GTR by surveying forest birds in 32 mid-rotation stands in southern Sweden, in which broadleaf GTR was present or absent. Complementing the many studies that have assessed GTR in clear-cuts, our results indicated that bird assemblages can also benefit from broadleaf GTR several decades after final felling in conifer dominated production stands. The GTR stands harboured a higher bird abundance and species richness than the control stands without GTR, and also appears to have benefited several important guilds, such as broadleaf-associated birds and cavity nesters. However, variation in the number trees retained, the species composition of retained trees, and their environmental context within the stand (e.g. density and proximity of surrounding production trees), limited our capacity to detect threshold requirements for GTR. In summary, our study provides a “glimpse into the future” as mid-rotation production stands with such old and large retained trees are unusual in today's landscape, but are expected to become more common in the decades to come, in Sweden and many other nations. Our study thereby provides provisional support for the continued and future use of this practice, and indicates that the biodiversity contribution of retention trees continues to occur several decades into the stand’s rotation.
... Hence, a tree is suitable for the establishment or improvement of a nest cavity when the wood is softened by fungal infection (in particular for smaller birds). This process takes time and thereby favours hollow formation in larger older trees (Courbaud et al., 2022). Although we did not survey retained trees for the occurrence of cavities, it is reasonable to assume a higher prevalence of these structures in retained trees than in the production trees due to their older age and larger size (Larrieu et al., 2014;Courbaud et al., 2022). ...
... This process takes time and thereby favours hollow formation in larger older trees (Courbaud et al., 2022). Although we did not survey retained trees for the occurrence of cavities, it is reasonable to assume a higher prevalence of these structures in retained trees than in the production trees due to their older age and larger size (Larrieu et al., 2014;Courbaud et al., 2022). The average DBH of the retained trees in our study was 34 cm, and close to 10% of all retained trees were larger than 50 cm. ...
... This hypothesis is consistent with other evidence that all trees eventually senesce, particularly with respect to the increasing probability of mortality [7]. However, it is also possible that the probability of developing defects remains constant or decreases over time, and that defects have simply accumulated over time with larger, older trees [8]. Indeed, the rate at which trees develop defects related to quality has never been quantified using longitudinal data in the northern hardwood forests of North America, meaning that the significance of the probability of decline in quality relative to tree size is fairly limited. ...
Northern hardwoods are susceptible to a wide range of defects that can reduce the amount of sound wood with desirable qualities, such as the clear sapwood of sugar maple trees. Yet, the rate at which trees decline in quality due to the development of such defects has never been quantified in northern hardwood forests due to a dearth of repeat inventories that record the appearance of defects over time. As a result, it remains uncertain whether, and how, selection management reduces the probability of decline in quality. In this study, we quantify the rate at which trees decline in quality due to the development of defects, and we test several hypotheses regarding the influence of selection management on quality. Our results show that (1) the probability of decline in quality increases as trees grow larger; (2) crown dieback also increases the probability of decline in quality; (3) the probability of decline in quality is slightly lower in managed stands than in unmanaged stands, and (4) the probability of decline in quality increases with the mean annual temperature of the site. Finally, we combined our estimates of the probability of decline in quality with previous estimates of the probability of mortality to assess the overall risk associated with retaining trees of different species, sizes, and vigour profiles. The resulting metric can inform efforts to improve the management of northern hardwood forests by providing an integrated estimate of the risk that the value of a tree will be reduced, or eliminated, due to mortality or decline in quality.
... Thus, time may not have been sufficient to develop new TreMs specific to deadwood. Previous studies predicted the formation rate of TreMs on living trees (Courbaud et al. 2017(Courbaud et al. , 2021, which increased with DBH for most of the TreM categories. However, reliable time series based on longitudinal observations are still needed to understand TreM development (formation and persistence) on both living and dead trees. ...
Retention of habitat trees is a common biodiversity conservation practice in continuous cover forests of temperate Europe. Commonly, living habitat trees are selected on the basis of their tree-related microhabitats (TreMs) such as cavities or crown deadwood. Owing to the increasing frequency and intensity of climate change-related disturbances, habitat trees in particular are expected to experience increased mortality rates. This may impact the long-term provisioning of TreMs. Here, we compared the TreM occurrence on living and dead trees to investigate whether dead trees support more and other TreMs than living trees. We also hypothesized that a combination of living and dead trees results in the most diverse stand-level TreM composition. We surveyed the TreM composition of living and dead habitat trees in 133 one-hectare plots in the Black Forest region managed according to a continuous cover approach. We fitted generalized linear mixed models to identify the main predictors of TreM occurrence to predict their abundance and richness. Tree identity (as a combination of species and vitality status) and diameter were the main drivers of TreM abundance and richness, which were highest on dead Abies alba. Even though dead A. alba and Picea abies supported TreM numbers similar to those provided by large living trees, their TreM composition was significantly different. This suggests that dead trees cannot substitute the habitat functions of living habitat trees, but they can complement them to increase the overall stand-level TreM diversity, in particular through decayed, large snags.
... In forests managed for timber production, trees are rarely allowed to grow old enough to develop large holes through damage or decay [48,49]. Therefore, species that require large tree holes for nesting usually rely on cavities excavated by woodpeckers [48,[50][51][52]. ...
European honeybee populations are considered to consist only of managed colonies, but recent censuses have revealed that wild/feral colonies still occur in various countries. To gauge the ecological and evolutionary relevance of wild-living honeybees, information is needed on their population demography. We monitored feral honeybee colonies in German forests for up to 4 years through regular inspections of woodpecker cavity trees and microsatellite genotyping. Each summer, about 10% of the trees were occupied, corresponding to average densities of 0.23 feral colonies km−2 (an estimated 5% of the regional honeybee populations). Populations decreased moderately until autumn but dropped massively during winter, so that their densities were only about 0.02 colonies km−2 in early spring. During the reproductive (swarming) season, in May and June, populations recovered, with new swarms preferring nest sites that had been occupied in the previous year. The annual survival rate and the estimated lifespan of feral colonies (n = 112) were 10.6% and 0.6 years, respectively. We conclude that managed forests in Germany do not harbour self-sustaining feral honeybee populations, but they are recolonized every year by swarms escaping from apiaries.
... 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]. ...
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.
... Among them, saproxylic beetles are a highly diverse group of insects that depend on dead or decaying wood for at least part of their life cycle and play important ecological roles by participating in carbon and nutrient cycles or by complexifying trophic chains (Stokland et al. 2012). However, current silvicultural practices tend to reduce deadwoodrelated resources and microhabitats (Siitonen 2001;Grove 2002;Paletto et al. 2014;Courbaud et al. 2022). As a consequence, saproxylic beetles are at considerable risk in intensively managed forests (Seibold et al. 2015;Grove 2002), and 17.9% of saproxylic beetle species are now considered threatened in Europe (Calix et al. 2018). ...
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.
... Measuring forest biodiversity is often done via the use of biodiversity indicators, such as volume of dead wood (Christensen et al., 2005) or more recently, via the measurement of TreMs (Bütler et al., 2020). 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. ...
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.
... In addition to the consequences for oak recruitment, wild boar predation is likely to have varying impact on recruitment across different tree species, depending on the tree species susceptibility to seed predation and herbivory. Such species-specific variation in the response to wild boar population reduction has the potential to affect forest community structure, biodiversity and carbon sequestration through changes in species dominance [42,43]. Considering the longevity of trees, the community-wide changes in recruitment can be discernible for a long time after the disease outbreak has passed, leaving a permanent footprint of the virus in the forest structure [41,44]. ...
There are several mechanisms that allow plants to temporarily escape from top-down control. One of them is trophic cascades triggered by top predators or pathogens. Another is satiation of consumers by mast seeding. These two mechanisms have traditionally been studied in separation. However , their combined action may have a greater effect on plant release than either process alone. In 2015, an outbreak of a disease (African swine fever, ASF) caused a crash in wild boar (Sus scrofa) abundance in Białowiezȧ Primeval Forest. Wild boar are important consumers of acorns and are difficult to satiate relative to less mobile granivores. We hypothesized that the joint action of the ASF outbreak and masting would enhance regeneration of oaks (Quercus robur). Data from ungulate exclosures demonstrated that ASF led to reduction in acorn predation. Tree seedling data indicated that oak recruitment increased twofold relative to pre-epidemic period. Our results showed that perturbations caused by wildlife disease travel through food webs and influence forest dynamics. The outbreak of ASF acted syner-gistically with masting and removed herbivore top-down control of oaks by mobile consumers. This illustrates that the ASF epidemic that currently occurs across Europe can have broad effects on forest dynamics.
Natural disturbances are an integral part of forest ecosystems. They ensure the creation of new habitats, maintain high spatial heterogeneity and disrupt the ecological succession processes. Forest ecosystems in a particular region are historically adapted to the disturbance complexes affecting that region (i.e. the disturbance regime). They are also largely affected by so-called anthropogenic disturbances (e.g. logging). The process of progressive tree death due to these different disturbances is called "forest dieback". Generally, these diebacks are followed by salvage or sanitation logging to harvest the commercial value of the trees before they deteriorate or to contain future pest outbreaks. This logging is considered to be additional disturbance. However, ongoing changes in climate and land use are leading to changes in the regime of these disturbances. In the extreme, if the change in these regimes is too great, it can lead to a shift towards a non-forest ecosystem. These regime shifts could then result in regional extinctions of forest species and alter the ecosystem services provided by forests to human societies. The study of these forest diebacks is therefore of central importance. In this thesis, we focus on the response of saproxylic beetles (i.e. beetles linked for part or all of their life cycle to dead wood), an ecological group threatened in temperate managed forests due to the scarcity of the dead wood resource. We also analyse habitat changes caused by these diebacks (i.e. disturbance legacies). For this purpose, we study three case studies of European dieback: (i) Pyrenean fir (Abies alba) and (ii) Loire Valley oak (Quercus spp.) caused by droughts, and (iii) Bavarian spruce (Picea abies) caused by storms and Ips typographus} outbreaks. On each of these sites, we inventoried the dead wood and tree-related microhabitats present on the plots as well as saproxylic beetles. These surveys revealed significant changes in habitats, resulting in increases in dead wood and changes in tree-related microhabitat composition. These changes appeared to be modulated by the severity of dieback. In cascade, these habitat changes induced modifications in the local composition of saproxylic beetles. For both coniferous forests, habitat changes induced positive effects of dieback on local beetle diversity, both taxonomic and functional. Furthermore, we observed homogenisations of saproxylic beetle communities in the landscape due to dieback. Furthermore, we highlighted the importance of dieback at the landscape scale on local taxonomic, functional and phylogenetic assemblages of saproxylic beetles. We also show that functional and phylogenetic diversity were mostly driven by landscape processes. Finally, we noted that sanitary and salvage logging did not affect local beetle diversity but strongly altered their ecological relationships. Our results highlight the value that can be gained from declining areas for the conservation of otherwise threatened species groups in managed forest areas, by maintaining the habitats created (i.e. dead wood and tree-related microhabitats). Finally, they highlight the need to consider the maintenance of these declining areas on a landscape scale.
Tree to tree interactions are important structuring mechanisms for forest community
dynamics. Forest management takes advantage of competition effects on tree growth by
removing or retaining trees to achieve management goals. Both competition and
silviculture have, thus, a strong effect on density and distribution of tree related
microhabitats which are key features for forest taxa at the stand scale. In particular,
spatially-explicit data to understand patterns and mechanisms of tree-related microhabitats formation in forest stands are rare. To train and eventually improve decision-making capacities related to the integration of biodiversity aspects into forest management plot of one hectare, so called marteloscopes were established in the frame of the ‘European Integrate Network’. In each plot, a set of data is collected at the individual tree level and stored in a database, the ‘I+ repository’. The 'I+ repository' is a centralised online database which serves for maintaining the data of all marteloscope plots. A subset of this repository was made publicly available via the Global Biodiversity Information Facility, based on a data-sharing policy. Data included are tree location in plot, tree species, forest mensuration data (diameter at breast height [cm], tree height [m]), tree status (living or standing dead) and tree-related microhabitats. Further, a visual assessment of timber quality classes is performed in order to provide an estimate of the economic value (market price) for each tree. This information is not part of the GBIF dataset.
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.
The implementation of biodiversity conservation measures in forests managed for timber production usually implies trade-offs between ecological and economic objectives. In continuous cover forestry these trade-offs emerge at the scale of selecting individual trees for timber harvesting or habitat retention. Tree selection determines both the economic viability of timber management and the prevalence of tree-related microhabitats, considered a multi-taxon indicator of forest biodiversity.
Recent studies find that tree selection is influenced by several factors, such as individual management preferences and goals, professional education and institutional context. To gain a deeper understanding of tree-selection practices in the context of retention forestry, we analyse four tree-selection exercises on silvicultural training sites (Marteloscopes) performed by groups with different professional backgrounds: conservationists, foresters, and students of each. Based on qualitative data from participant observations and group discussions, we explore their decision-making strategies, reasoning, and practices. Our analysis provides novel insights into decision-making processes when implementing conservation measures, especially with regard to dealing with trade-offs and uncertainties.
Our findings indicate that tree-selection decisions are not merely the result of cognitive and rational weighing processes. They can be understood as practices requiring experience, professional routine, and intuition. These practices differ across professional cultures. Despite these differences, the participants of the analysed Marteloscope exercises developed an understanding of the other stakeholders’ motivations and restrictions. The setting stimulated a change of perspective that built awareness in many of the participants of their own routines and biases. This may facilitate professional cooperation, cross-disciplinary learning, and the implementation of biodiversity conservation.
Primeval forests in the temperate zone exist only as a few remnants, but theses serve as important reference areas for conservation. As key habitats, tree-related microhabitats (TreMs) are of intense interest to forest ecologists, but little is known about their natural composition and dynamics in different tree species. Beech forms a major part of the temperate forests that extend from Europe, home to European beech Fagus sylvatica L. (Fs), eastward to Iran, where Oriental beech Fagus orientalis Lipsky (Fo) is the dominant species. In this study, we compared TreMs in primeval forests of both species, using data from Fo growing in 25 inventory plots throughout the Hyrcanian forest belt in Iran and from Fs growing in a 9 ha permanent plot in the Uholka Forest of Ukraine. TreMs based on 47 types and 11 subgroups were recorded. Beech trees in the Hyrcanian forest had a higher mean diameter at breast height (dbh) than beech trees in Uholka and contained twice as many TreMs per hectare. Although the mean richness of TreMs per TreM bearing tree was similar in the two species, on the basis of the comparison single trees in two groups (n = 405 vs. 2251), the composition of the TreMs clearly differed, as the proportions of rot holes, root-buttress concavities, and crown deadwood were higher in the Hyrcanian Forest, and those of bark losses, exposed heartwood, and burrs and cankers higher in Uholka Forest. Estimates of TreMs dynamics based on dbh and using Weibull models showed a significantly faster cumulative increase of TreMs in Fo, in which saturation occurred already in trees with a dbh of 70-80 cm. By contrast, the increase in TreMs in Fs was continuous. In both species, the probability density was highest at a dbh of about 30 cm, but was twice as high in Fo. Because of limitations of our study design, the reason behind observed Forests 2020, 11, 144 2 of 13 differences of TreM formation and composition between regions remains unclear, as it could be either result of the tree species or the environment, or their interaction. However, the observed differences were more likely the result of differences in the environment than in the two tree species. Nevertheless, our findings demonstrate that the Hyrcanian Forest, recently designated as a natural heritage site in Iran, is unique, not only as a tertiary relict or due to its endemic trees, herbs and arthropods, but also because of its TreMs, which form a distinct and rich habitat for associated taxa, including endemic saproxylic species.
Managing forests to preserve biodiversity requires a good knowledge not only of the factors driving its dynamics but also of the structural elements that actually support biodiversity. Tree-related microhabitats (e.g. cavities, cracks, conks of fungi) are tree-borne features that are reputed to support specific biodiversity for at least a part of species' life cycles. While several studies have analysed the drivers of microhabitats number and occurrence at the tree scale, they remain limited to a few tree species located in relatively narrow bio-geographical ranges. We used a nationwide database of forest reserves where microhabi-tats were inventoried on more than 22,000 trees. We analysed the effect of tree diameter and living status (alive or dead) on microhabitat number and occurrence per tree, taking into account biogeoclimatic variables and tree genus. We confirmed that larger trees and dead trees bore more microhabitats than their smaller or living counterparts did; we extended these results to a wider range of tree genera and ecological conditions than those studied before. Contrary to our expectations, the total number of microhabitat types per tree barely varied with tree genus-though we did find slightly higher accumulation levels for broad-leaves than for conifers-nor did it vary with elevation or soil pH, whatever the living status. We observed the same results for the occurrence of individual microhabitat types. However, accumulation levels with diameter and occurrence on dead trees were higher for microhabi-tats linked with wood decay processes (e.g. dead branches or woodpecker feeding holes) than for other, epixylic, microhabitats such as epiphytes (ivy, mosses and lichens)
The most significant European forest-related strategies highlight the importance of multifunctional forests for human wellbeing, due to the provision of a wide range of goods and services. However, managing competing aims, such as timber production, economic drivers and biodiversity conservation is often difficult for practitioners. In order to assess the loss and gain of ecosystem services caused by forestry, trade-off evaluation has been increasingly used to aid decision-making. In this study, four silvicultural scenarios are simulated using the Marteloscope approach to evaluate the trade-offs between biodiversity conservation and timber production. Tree-related Microhabitats (TreMs) are used as a proxy to evaluate forest habitat value, while timber production is assessed by the number of harvested trees, biomass removal and economic income. This study takes an innovative approach by investigating TreMs using the Marteloscope in mixed Mediterranean forest. The main findings from this paper confirm that tree-related microhabitats can be considered ecological indicators effective in identifying important habitat trees, to assess forest habitat value and support tree marking for thinning operations and management.
Many small terrestrial vertebrates exhibit limited spatial movement and are considerably exposed to changes in local environmental variables. Among such vertebrates, amphibians at present experience a dramatic decline due to their limited resilience to environmental change. Since the local survival and abundance of amphibians is intrinsically related to the availability of shelters, conservation plans need to take microhabitat requirements into account. In order to gain insight into the terrestrial ecology of the spectacled salamander Salamandrina perspicillata and to identify appropriate forest management strategies, we investigated the salamander’s seasonal variability in habitat use of trees as shelters in relation to tree features (size, buttresses, basal holes) and environmental variables in a beech forest in Italy. We used the occupancy approach to assess tree suitability on a non-conventional spatial scale. Our approach provides fine-grained parameters of microhabitat suitability and elucidates many aspects of the salamander’s terrestrial ecology. Occupancy changed with the annual life cycle and was higher in autumn than in spring, when females were found closer to the stream in the study area. Salamanders showed a seasonal pattern regarding the trees they occupied and a clear preference for trees with a larger diameter and more burrows. With respect to forest management, we suggest maintaining a suitable number of trees with a trunk diameter exceeding 30 cm. A practice of selective logging along the banks of streams could help maintain an adequate quantity of the appropriate microhabitat. Furthermore, in areas with a presence of salamanders, a good forest management plan requires leaving an adequate buffer zone around streams, which should be wider in autumn than in spring.
The runjags package provides a set of interface functions to facilitate running Markov chain Monte Carlo models in JAGS from within R. Automated calculation of appropriate convergence and sample length diagnostics, user-friendly access to commonly used graphical outputs and summary statistics, and parallelized methods of running JAGS are provided. Template model specifications can be generated using a standard lme4-style formula interface to assist users less familiar with the BUGS syntax. Automated simulation study functions are implemented to facilitate model performance assessment, as well as drop-k type cross-validation studies, using high performance computing clusters such as those provided by parallel. A module extension for JAGS is also included within runjags, providing the Pareto family of distributions and a series of minimally-informative priors including the DuMouchel and half-Cauchy priors. This paper outlines the primary functions of this package, and gives an illustration of a simulation study to assess the sensitivity of two equivalent model formulations to different prior distributions.
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.
Ecological models are increasingly used as decision-making tools and their reliability is becoming a key issue. At the same time, the sophistication of techniques for model development and analysis has given rise to a relative compartmentalization of model building and evaluation tasks. Several guidelines invite ecological modelers to follow an organized sequence of development and analysis steps and have coined the term " evaludation " for this process. The objective of this paper is to assess the feasibility and the value of a structured evaludation process, based on the working example of the Samsara2 model, a spatially explicit individual-based forest dynamics model. We implemented the six steps of model design, process level calibration, qualitative evaluation, quantitative evaluation, global sensitivity analysis, and partial recalibration using approximate Bayesian computing. We then evaluated how the evaludation process revealed model strengths and weaknesses, specified the model's conditions of use, clarified how the model works, and provided insights into forest ecosystem functioning. Finally, the efficiency/cost ratio of the process and future improvements are discussed.
Industrial forestry typically leads to a simplified forest structure and altered species composition. Retention of trees at harvest was introduced about 25 years ago to mitigate negative impacts on biodiversity, mainly from clearcutting, and is now widely practiced in boreal and temperate regions. Despite numerous studies on response of flora and fauna to retention, no comprehensive review has summarized its effects on biodiversity in comparison to clearcuts as well as un-harvested forests.Using a systematic review protocol, we completed a meta-analysis of 78 studies including 944 comparisons of biodiversity between retention cuts and either clearcuts or un-harvested forests, with the main objective of assessing whether retention forestry helps, at least in the short-term, to moderate the negative effects of clearcutting on flora and fauna.Retention cuts supported higher richness and a greater abundance of forest species than clearcuts as well as higher richness and abundance of open-habitat species than un-harvested forests. For all species taken together (i.e. forest species, open-habitat species, generalist species and unclassified species) richness was higher in retention cuts than in clearcuts.Retention cuts had negative impacts on some species compared to un-harvested forest, indicating that certain forest-interior species may not survive in retention cuts. Similarly, retention cuts were less suitable for some open-habitat species compared with clearcuts.Positive effects of retention cuts on richness of forest species increased with proportion of retained trees and time since harvest but there were not enough data to analyse possible threshold effects, i.e. levels at which effects on biodiversity diminish. Results for different comparisons were largely consistent among taxonomic groups for forest and open-habitat species, respectively.Synthesis and applications. Our meta-analysis provides support for wider use of retention forestry since it moderates negative harvesting impacts on biodiversity. Hence, it is a promising approach for integrating biodiversity conservation and production forestry although identifying optimal solutions between these two goals may need further attention. Nevertheless, retention forestry will not substitute for conservation actions targeting certain highly specialized species associated with forest-interior or open-habitat conditions.This article is protected by copyright. All rights reserved.
Recent studies have highlighted the key role of tree microhabitats in forest habitat complexity and have suggested using them as surrogates for local taxonomic biodiversity. However, few practical guidelines have been published to help foresters in managing microhabitats at the stand scale. This paper provides scientific background information to help to develop such guidelines. We surveyed trees in nine long-unmanaged beech–fir forests to model tree microhabitat occurrence and diversity at the tree level. Data were upscaled to a size range of tree cluster, i.e., at the tree population scale, by aggregating observed values of microhabitat occurrence. Accumulation curves were used to estimate the minimum number of trees required to make all the microhabitat types available. Two managed forests were then studied to quantify management effects on microhabitats. Diameter at breast height (dbh) and tree species, respectively, explained 16 and 10 % of the variations in the number of microhabitat-bearing trees, and 21 and 10 % for the number of microhabitat types. Beech trees and firs with a dbh of less than dbh 50 and 65 cm, respectively, did not ensure the provision of all microhabitat types. At least 20 ha of unmanaged forest were necessary to conserve all the microhabitat types. Current management practices have reduced the number of microhabitat-bearing beeches both by reducing the number of very large trees (dbh > 67.5 cm) and by tree selection within mid-size diameters. For fir, only the logging of very large trees (dbh > 62.5 cm) negatively affected microhabitats. These figures may inspire guidelines for conservation-friendly forestry.
The study of insects inhabiting basal hollow trees presents a methodological challenge inducing the fact that there is very little research done on fauna of this habitat. Many endangered saproxylic species only develop in cavities located at ground level. One of the most emblematic species of the kind is the Violet Click Beetle (Limoniscus violaceus), included in Annex II of the UE “Habitats” Directive. Surveys have been conducted in five Natura 2000 areas using a new method to monitor L. violaceus: the emergence traps. A total of 376 beetle species, including 239 saproxylics, have been identified. Five are considered threatened and are registered on the European Red List of saproxylic beetles and three are included in Annex II of the “Habitats” Directive. Among 191 trees studied, 33 revealed the presence of L. violaceus. Sampling efforts required to detect at least one specimen have been evaluated. Our results show that sampling a minimum of 20 hollow trees in April and May with emergence traps is recommended to obtain a meaningful survey on the presence of the Violet Click Beetle.
Because quantitative data on the distribution of whole microhabitat sets are still lacking to indirectly assess taxonomic biodiversity in forests, we studied the distribution of seven key microhabitat types in 10 montane European beech (Fagus sylvatica L.) – silver fir (Abies alba Mill.) forests (Pyrénées, France) that had not been harvested for several decades. We examined 2105 live trees and 526 snags. Frequencies of cavities and dendrothelms were significantly higher on live beech than on fir. Sap runs were strictly found on live fir. Frequencies of cracks and saproxylic fungi were significantly higher on snags than on live trees. Seventy percent of live beeches but only 18% of firs carried one or more microhabitats. For both beech and fir and for each microhabitat type, we found, using the recursive partitioning method, one to three diameter thresholds that each corresponded to a significant change in the probability of microhabitat presence. When considering the whole microhabitat set, the most significant diameter thresholds were 42, 60, 73, and 89 cm for beech and 99 cm for fir. We suggest that forest managers conserve (i) mixed stands and (ii) beech with a diameter at breast height >90 cm and fir >100 cm. These rules should be adapted for each forest ecosystem.
In contemporary forest management, also of commercial forests, threshold values are widely used for consideration of biodiversity
conservation. Here, we present various aspects of dead-wood threshold values. We review published and unpublished dead-wood
threshold data from European lowland beech–oak, mixed-montane, and boreo-alpine spruce–pine forests separately to provide
managers of European forests with a baseline for management decisions for their specific forest type. Our review of dead-wood
threshold data from European forests revealed 36 critical values with ranges of 10–80m3ha−1 for boreal and lowland forests and 10–150m3ha−1 for mixed-montane forests, with peak values at 20–30m3ha−1 for boreal coniferous forests, 30–40m3ha−1 for mixed-montane forests, and 30–50m3ha−1 for lowland oak–beech forests. We then expand the focus of dead-wood threshold analyses to community composition. We exemplify
the two major statistical methods applied in ecological threshold analysis to stimulate forest researchers to analyze more
of their own data with a focus on thresholds. Finally, we discuss further directions of dead-wood threshold analysis. We anticipate
that further investigations of threshold values will provide a more comprehensive picture of critical ranges for dead wood,
which is urgently needed for an ecological and sustainable forestry.
KeywordsThresholds-Conditional inference tree-Maximally selected rank statistic-Logistic regression-Bootstrapping-Variable selection
In forest ecosystems, the level of biodiversity is strongly linked to dead wood and tree microhabitats. To evaluate the influence
of current forest management on the availability of dead wood and on the abundance and distribution of microhabitats, we studied
the volume and diversity of dead wood objects and the distribution and frequency of cavities, dendrothelms, cracks, bark losses
and sporophores of saproxylic fungi in montane beech-fir stands. We compared stands unmanaged for 50 or 100years with continuously
managed stands. A total of 1,204 live trees and 460 dead wood objects were observed. Total dead wood volume, snag volume and
microhabitat diversity were lower in the managed stands, but the total number of microhabitats per ha was not significantly
different between managed and unmanaged stands. Cavities were always the most frequent microhabitat and cracks the least frequent.
Dendrothelm and bark loss were favored by management. Beech (Fagus sylvatica) carried many more microhabitats than silver fir (Abies alba), especially cavities, dendrothelms and bark losses. Fir very scarcely formed dendrothelms. Secondary tree species played
an important role by providing cracks and bark losses. The proportion of microhabitat-bearing trees increased dramatically
above circumference thresholds of 225cm for beech and 215cm for fir. Firs with a circumference of less than 135cm did not
carry microhabitats. In order to conserve microhabitat-providing trees and to increase the volume of dead wood in managed
stands, we recommend conserving trees that finish their natural cycle over 10–20% of the surface area.
KeywordsDead wood–Cavity–Crack–Dendrothelm–Bark loss–Girth threshold
Tree care, especially pruning, is still mostly done in the dormant time. Such treatments expose live inner bark, the vascular cambium, and functioning outer sapwood to harsh external influences followed often by infection of pathogens. Investigations about response reactions of beech and oak to wounding made in different times of the year showed that wound closure was significantly slower for December and February wounds than in April and October. The length of discoloured sapwood was in October and December wounds greater than in February and April. Sapwood reaction expressed by the soluble phenol concentration index indicated however no significant differences among wounding dates. Overall, woundings in the vegetation period will be more effectively compartmentalized than in the dormant season. Consequently, tree care like pruning with many woundings should not be done in the winter period.
Mechanical forces active on steep slopes tend to overturn plants, which respond by developing a specific asymmetrical architecture
in the root system. This asymmetric architecture is the consequence of preferential lateral root emergence and elongation
in the up-slope and down-slope directions. Root systems show a normal symmetrical architecture when the same species is grown
on plane soil. The asymmetrical root architecture on steep slopes seems to increase the plant's stability by modifying the
distribution of mechanical forces into the soil. This hypothesis is supported by the observation that lateral roots developing
in the up-slope or down-slope directions present considerable anatomical modifications in shape and tissue-organization compared
with lateral roots from plants growing on plane soil.
Key message
On the selected sites in the investigated Oriental beech (
Fagus orientalis
L.) dominated forests in Iran with an extensive individual tree selection system, tree microhabitats (MH) are more influenced by tree level factors such as tree species and DBH than by plot level factors such as plot basal area or size and species diversity.
Context
Despite the ecological importance of tree microhabitats for biodiversity, there is a lack of information about the occurrence of microhabitat features in Hyrcanian forests in Northern Iran.
Aims
The aims of this study were to assess selected MH types on living trees in forests managed with an individual tree selection system and forests unmanaged since at least 30 years and to study the effect of tree and plot level factors on their occurrence.
Methods
A total of 120 circular sample plots were used to collect tree level microhabitat information at six different sites in Oriental beech forests in Iran. Pairs of managed and recently unmanaged forests were located at six sites. Generalized linear mixed models were employed to analyze (i) the effect of management on microhabitat occurrence, and (ii) to explain the occurrence of microhabitats at tree level.
Results
There was no significant difference in total number of assessed microhabitats per ha in forests managed with a low-intensity management regime with individual tree selection versus recently unmanaged forests (no management intervention for at least 30 years). Stem cavity with decay was by far the most frequent microhabitat type in managed (16.5 per ha) as well as in recently unmanaged forests (14.2 per ha). Hornbeam and oak trees have a higher probability to host microhabitats (bark loss, woodpecker cavity, and stem cavities) than the dominant oriental beech. Suppressed trees indicated by basal area of larger trees have a lower probability to show bark loss and conks of fungi.
Conclusion
Models of microhabitat occurrence on trees have potential to support the development of management guidelines to foster biodiversity.
In northern Mediterranean forests, increasing drought stress due to the on-going climate change is combined with stand ageing due to the lack of management. Management by thinning may alleviate drought stress by reducing competition, but its application is challenging in coppices of resprouting species where its long-term consequences for tree demography and stand dynamics are difficult to evaluate. In this study, we investigate the long-term (15 years) demographic responses of holm oak (Quercus ilex L.) to a combination of thinning from below (−30% basal area) and experimental rainfall exclusion (−27% precipitation). Stem growth, survival and resistance to an extreme drought event were positively linked to both stem size and local competition release after thinning. Thinning improvement of growth and survival were thus due to both a selection of the biggest, most vigorous, trees and to a release of competition for water. Rainfall exclusion, on the other hand, led to a shift of the tree size-mortality relationship, which resulted in the death of bigger trees, in a faster loss of stool density and in a slower evolution of the stand basal area compared to the control. Thinning was beneficial by cancelling the rainfall exclusion effects on growth and mortality, and by doubling the stand basal area increment compared to unthinned control. The initial loss of stools due to thinning was compensated by a lower mortality, suggesting that thinning do not reduce further the amount of unique genotypes on the long-term. Positive thinning effects on stem growth decreased over time but remained significant 15 years after thinning, while resprouting dynamics strongly decreased with time. These results indicate that moderate thinning from below is a relevant strategy to increase stem vitality and stand production in old coppices, particularly in a context of a chronic rise in drought stress and more frequent extreme drought episodes.
Retaining trees during harvesting to conserve biodiversity is becoming increasingly common in forestry. To assess, select and monitor these habitat trees, ecologists and practitioners often use Tree-related Microhabitats (TreMs), which are assumed to represent the abundance and diversity of environmental resources for a wide range of forest-dwelling taxa. However, the relationship between TreMs and forest organisms is not fully understood. In this context, we attempted to identify and quantify the links between TreMs and three groups of forest organisms: insects, bats, and birds. Specifically, we tested whether species abundance is influenced by TreM abundance, either as direct predictor or as mediator of environmental predictors.
We collected data in 86 temperate, 1-ha mixed forest plots and employed a hierarchical generalized mixed model to assess the influence of seven environmental predictors (aspect, number and height of standing dead trees, cover of herb and shrub layer, volume of lying deadwood, and terrain ruggedness index (TRI)) on the abundance of TreMs (15 groups) on potential habitat trees, insects (10 orders), bats (5 acoustic groups) and birds (29 species) as a function of seven environmental predictors: aspect, number and height of standing dead trees, cover of herb and shrub layer, volume of lying deadwood, and terrain ruggedness index (TRI). This allowed us to generate a correlation matrix with potential links between abundances of TreMs and co-occurring forest organisms. These correlations and the environmental predictors were tested in a structural equation model (SEM) to disentangle and quantify the effects of the environment from direct effects of TreMs on forest organisms.
Four TreM groups showed correlations > |0.30| with forest organisms, in particular with insects and bats. Rot holes and concavities were directly linked with three insect groups and two bat groups. Their effect was smaller than effects of environmental predictors, except for the pairs “rot holes – Sternorrhyncha” and “rot holes – bats” of the Pipistrellus group. In addition, TreMs had indirect effects on forest organisms through mediating the effects of environmental predictors.
We found significant associations between two out of fifteen TreM groups and five out of 44 forest organism groups. These results indicate that TreM abundance on potential habitat trees is not suited as a general indicator of the species abundance across broad taxonomic groups but possibly for specific target groups with proven links.
It is widely accepted that climate change will see an increase in the frequency and intensity of drought events that will inevitably impact on the commercially-important coniferous forests in Western Europe. Of particular concern is the likely increase in the incidence of drought-induced, radial-longitudinal stem cracks that will have serious consequences for forest health and wood structural properties. This paper reviews the existing knowledge on drought-induced stem cracking in coniferous species. It summarises the current impact of drought on coniferous forests and predicted future impacts of a changing climate. Available information on the mechanism of radial splitting and the role of wood properties in this process is examined. It also considers the influence of soil properties on the development of drought stress within trees associated with stem cracking. The final part of the review discusses the knowledge gaps and suggestions for further research.
To encourage forest managers to use biodiversity indicators in their work, providing environmental variables that depict species habitats, have well-calibrated and strong relationships with biodiversity and are easy to routinely record would be a step forward. The Index of Biodiversity Potential (IBP) is a rapid habitat assessment method widely used in France. It uses ten variables that indicate potential habitat for forest-dwelling species and is easy for forest managers to implement during their day-today activities. The objective of this paper is to evaluate the indicator power of these IBP variables at the stand scale, i.e. their capacity to co-vary with empirical species richness and composition data for nine taxa. The data were obtained from 487 plots set up in 19 forested areas in France. Taxonomic data focused on corticolous lichens, corticolous and saproxylic bryophytes, poly-pores, saproxylic beetles, ground beetles, hoverflies, birds, bats and vascular plants. For the latter five taxa, we built subgroups of forest-specialist species. The IBP variables were recorded on 1-ha circular plots centered on the sampling point used to record taxonomic data. We explored the relationships between the IBP variables and species composition/richness of nine taxa at the stand scale. Furthermore, we searched for threshold values for all the significant relationships found between species richness and the IBP variables. Variations in the species composition of vascular plants and saproxylic beetles, and to a lesser extent, polypores, bats and lichens, were significantly related to habitat variations (ranked according to the Procrustes significance level). The contribution of the IBP variables to the total inertia of species composition was about 18.7% on average. The IBP variables had a lower number of significant relationships with species richness than with species composition. Unexpectedly, the forest subgroups mainly showed fewer significant relationships with habitat variables than did the full-groups, both for species richness and composition. We highlighted seven significant thresholds in the habitat variables above which species richness was significantly higher. Finally, we recommend that forest managers (i) routinely use a rapid habitat assessment such as the IBP, (ii) orient silvicultural practices to ensure conservation of autochtonous tree species, large logs and different types of aquatic habitats above the thresholds highlighted in this study, and (iii) periodically complete a biodiversity assessment at the forest scale by recording taxonomic data.
Tree cavities are a critical multi‐annual resource that can limit populations and structure communities of cavity‐nesting vertebrates. We examined the regional and local factors influencing lifetime productivity (number and richness of occupants) of individual tree cavities across two divergent forest ecosystems: temperate mixed forest in Canada and subtropical Atlantic Forest, Argentina. We predicted that (1) species would accumulate more rapidly within cavities in the species‐rich system (Argentina: 76 species) than the poorer system (Canada: 31 species), (2) cavity characteristics associated with nest‐site selection in short‐term studies would predict lifetime cavity‐productivity, and (3) species would accumulate more rapidly across highly‐used cavities than across cavities used only once, and in Argentina than in Canada. We monitored and measured nesting cavities used by birds and mammals over 22 breeding seasons (1995–2016) in Canada and 12 breeding seasons (2006–2017) in Argentina. Cavities were used an average of 3.1 times by 1.7 species in Canada and 2.2 times by 1.4 species in Argentina. Species richness within cavities increased with number of nesting events at similar rates in Canada and Argentina, in both cases much slower than expected if within‐cavity species assemblages were random, suggesting that lifetime richness of individual cavities is more strongly influenced by local ecological factors (nest site fidelity, nest niche) than by the regional species pool. The major determinant of lifetime cavity productivity was the cavity's lifespan. We found only weak or inconsistent relationships with cavity characteristics selected by individuals in short‐term nest‐site selection studies. Turnover among (vs. within) cavities was the primary driver of diversity at the landscape scale. In Canada, as predicted, species accumulation was fastest when sampling across high‐use cavities. In Argentina, the rates of species accumulation were similar across high‐ and low‐use cavities, and fastest when both high‐ and low‐use cavities were pooled. These findings imply that biodiversity of cavity nesters is maintained by a mix of long‐lived (highly productive, legacy trees) and many high‐turnover (single‐use, fast decaying) tree cavities. Conservation of both long‐lasting and single‐use cavities should be incorporated into decisions about stand‐level forest management, regional land use policies, and reserve networks. This article is protected by copyright. All rights reserved.
The continued provision of old-growth elements in forest landscapes is a critical factor for biodiversity conservation in Central Europe. A well-established method for predicting the potential of forests to maintain biodiversity is to quantify tree-related microhabitat structures (TreMs). Our aim was to predict the TreM abundance and diversity for collectives of TreM-bearing trees; here 15 large trees per plot that were preselected by the largest crown sizes using remote sensing information. TreMs were inventoried on 2085 living trees across 139 plots (each 1 ha) in montane forests of the Black Forest, southwest Germany according to a detailed catalogue comprising 64 different TreM structures. We tested the influence of forest management, forest cover in the surrounding landscape (25 km radius), forest type, the number of standing dead trees, altitude and mean diameter at breast height (DBH) on the abundance and diversity of TreMs on living trees. All plots are managed or have been recently (20-40 yrs) abandoned from management. Generalized linear models (GLM) were used to identify the drivers of abundance and diversity of TreMs. The abundance of TreMs borne by the 15 large trees per plot is greater on plots located at higher altitudes. Increasing mean DBH leads to significantly higher abundance and diversity of TreMs. Groups of TreM-bearing trees in monospecific coniferous forests have the highest abundance but those in mixed-coniferous-broadleaved forests have the greatest diversity of TreMs. The occurrences of 11 out of 64 specific TreM structures were related to forest management, forest type, altitude or mean DBH. Large branch holes and buttress cavities increased with mean DBH and were found more frequently in mixed-coniferous-broadleaved forests than in the other forest types. The abundance of epiphytes on TreM bearing trees increased with altitude. This study demonstrates that the average abundance and diversity of TreMs can be predicted with readily available forest attributes. Additionally, the occurrence of specific TreMs could be described with the variation in these selected forest attributes.
1.National and international forest biodiversity assessments largely rely on indirect indicators, based on elements of forest structure that are used as surrogates for species diversity. These proxies are reputedly easier and cheaper to assess than biodiversity. Tree microhabitats – tree‐borne singularities such as cavities, conks of fungi or bark characteristics – have gained attention as potential forest biodiversity indicators. However, as with most biodiversity indicators, there is a lack of scientific evidence documenting their quantitative link with the biodiversity they are supposed to assess. 2.We explored the link between microhabitat indices and the richness and abundance of three taxonomic groups: bats, birds, and saproxylic beetles. Using a nation‐wide multi‐taxon sampling design in France, we compared 213 plots located inside and outside strict forest reserves. We hypothesized that the positive effect setting aside forest reserves has on biodiversity conservation is indirectly due to an increase in the proportion of large structural elements (e.g. living trees, standing and lying deadwood). These, in turn, are likely to favour the quantity and diversity of microhabitats. We analysed the relationship between the abundance and species richness of different groups and guilds (e.g. red‐listed species, forest specialists, cavity dwellers) and microhabitat density and diversity. We then used confirmatory structural equation models to assess the direct and indirect effects of management abandonment, large structural elements and microhabitats on the biodiversity of the target species. 3.For several groups of birds and bats, the indirect effect of management abandonment and large structural elements on biodiversity was mediated by microhabitats. However, the magnitude of the link between microhabitat indices and biodiversity was moderate. In particular, saproxylic beetles’ biodiversity was poorly explained by microhabitats, large structural elements or management abandonment. 4.Synthesis and applications. Tree microhabitats may serve as indicators for bats and birds, but they are not a universal biodiversity indicator. Rather, compared to large structural elements, they most likely have a complementary role to biodiversity. In terms of forest management and conservation, preserving diversity of microhabitats at the local scale benefits several groups of both bats and birds. This article is protected by copyright. All rights reserved.
Tree-related microhabitats (TreMs) are important features for the conservation of biodiversity in forest ecosystems. Although other structural indicators of forest biodiversity have been extensively studied in recent decades, TreMs have often been overlooked, either due to the absence of a consensual definition or a lack of knowledge. Despite the increased number of TreM studies in the last decade, the role of drivers of TreM profile in primary forests and across different geographical regions is still unknown. To evaluate the main drivers of TreM density and diversity, we conducted the first large-scale study of TreMs across European primary forests. We established 146 plots in eight primary forests dominated by European beech (Fagus sylvatica L.) in the Carpathian and Dinaric mountain ranges. Generalized linear mixed effect models were used to test the effect of local plot characteristics and spatial variability on the density and diversity (alpha, beta, and gamma) of TreMs. Total TreM density and diversity were significantly positively related with tree species richness and the proportion of snags. Root mean square tree diameters were significantly related to alpha and gamma diversity of TreMs. Both regions reached similarly high values of total TreM densities and total TreM densities and diversity were not significantly different between the two regions; however, we observed between the two regions significant differences in the densities of two TreM groups, conks of fungi and epiphytes. The density and diversity of TreMs were very high in beech-dominated mountain primary forests, but their occurrence and diversity was highly variable within the landscapes over relatively short spatial gradients (plot and stand levels). Understanding these profile provides a benchmark for further comparisons, such as with young forest reserves, or for improving forest management practices that promote biodiversity.
Cross-taxon surrogacy (between-taxon similarities in species patterns) can help conservation biologists to design simplified, standardized and efficient tools for biodiversity monitoring. Our study aims to identify potential sets of indicator taxa to be recommended in temperate forests. We focused on nine forest taxa: vascular plants, bryophytes, saproxylic beetles, polypores, lichens, ground beetles, hoverflies, birds and bats. We assessed crosstaxon congruence patterns, in terms of both alpha and beta-diversity, using empirical biodiversity data from 206 plots in ten French forested areas. We evaluated the cost-efficiency of potential surrogate taxa using both strictly encoded expert knowledge and results of this study. The most congruent taxa in alpha-diversity were bryophytes (with bats and polypores), and ground beetles (with bats and saproxylic beetles), though levels of covariation were mostly weak. The most congruent taxon in beta-diversity was vascular plants (with bryophytes, ground beetles, lichens and forest birds). Contrary to our expectations, the subsets of forest species within a given taxon exhibited a lower surrogacy than the taxon as a whole. Four categories of taxa were delineated based on costefficiency scores – from costless but ineffective (bats and ground beetles) to costly but effective (saproxylic beetles and polypores). No single taxon was firmly identified as a relevant surrogate for other taxa; using a set of two or three taxa drastically increased surrogacy, compared with single-taxon approaches. Saproxylic beetles associated with vascular plants, or with both vascular plants and birds, seemed to be the most cost-efficient associations. Further research is required to up-scale our results from the short-term, local scale to the long-term, landscape scale in European temperate forests.
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.
1. Tree-related microhabitats (TreMs), such as trunk cavities, peeled bark, cracks or sporophores of lignicolous fungi, are essential to support forest biodiversity because they are used as substrate, foraging, roosting or breeding places by bryophytes, fungi, invertebrates and vertebrates. Biodiversity conservation requires the continuous presence of TreMs in a forest. However, little is known about their dynamics. Moreover, we usually have only cross-sectional TreM data (observations of many trees at a single time), making it difficult to estimate TreM formation rates.
Fossils document the existence of trees and wood-associated organisms from almost 400 million years ago, and today there are between 400,000 and 1 million wood-inhabiting species in the world. This is the first book to synthesise the natural history and conservation needs of wood-inhabiting organisms. Presenting a thorough introduction to biodiversity in decaying wood, the book studies the rich diversity of fungi, insects and vertebrates that depend upon dead wood. It describes the functional diversity of these organisms and their specific habitat requirements in terms of host trees, decay phases, tree dimensions, microhabitats and the surrounding environment. Recognising the threats posed by timber extraction and forest management, the authors also present management options for protecting and maintaining the diversity of these species in forests as well as in agricultural landscapes and urban parks.
A study of the ecology of water-filled tree-holes in beech trees in Wytham Woods, Berkshire has been made and some of the results are presented here. A review of work and observations on similar aquatic habitats associated with plants is included and the paper concludes by considering the position of water-filled tree-holes in the woodland ecosystem. (1) Water-filled tree-holes are the most common aquatic habitats occurring in plants in the temperate zone. They vary greatly in size and occur at all heights from the ground. They are especially common in beech trees but are recorded from a large variety of other species. They are of two types basically, pans and rot-holes, and contain layers of rotting vegetation, fallen leaves and rain-water. (2) Six species of insect pass their immature stages in the tree-holes studied. Five of these are Diptera and the sixth, a beetle. All these larvae are saprophagous and largely restricted to tree-holes. (3) All species of larvae studied are present at all times of the year but all except the beetle, Prionocyphon serricornis, show marked seasonal fluctuations. The most numerous species, the chironomid Metriocnemus martinii, appears to have up to three generations each year while the other species of Diptera have only a single one. It is suggested that Prionocyphon may take two or more years to complete a single generation. (4) Most species pass the winter as quiescent larvae or adults but the ceratopogonid, Dasyhelea dufouri, has larvae which actively feed, grow and develop during the winter. (5) Densities of all species are higher in holes in the canopy layer (i.e. above c. 2 m) possibly because the quality of the detritus as food is higher in these holes. (6) Densities of larvae in the smaller holes are generally higher than in the larger holes. This is unexplained but possible reasons connected with food availability, microclimate and density of eggs are suggested. (7) Tree-holes are put forward as examples of `discrete habitats' and their fauna show characteristics which are also attributable to the inhabitants of other discrete habitats. (8) Water-filled tree-holes and their fauna have many connections, both direct and indirect, with other parts of the woodland ecosystem. There are connections with the canopy-layer via leaf-fall, with the leaf-litter via drifting, and with the soil via rain-splashing. The adult insects that emerge from tree-holes must feed and require vegetation, flowers or, in some species, other animals to provide this food. They are exposed to various dangers in the woodland such as predation, desiccation or drowning in rain-water. Some species require hibernation sites and Myiatropa florea requires a pupation site outside the tree-hole. Dasyhelea larvae have an alternative habitat in the form of slime-fluxes or sap-flows which occur elsewhere in the woodland.
From the reviews of the First Edition."An interesting, useful, and well-written book on logistic regression models . . . Hosmer and Lemeshow have used very little mathematics, have presented difficult concepts heuristically and through illustrative examples, and have included references."—Choice"Well written, clearly organized, and comprehensive . . . the authors carefully walk the reader through the estimation of interpretation of coefficients from a wide variety of logistic regression models . . . their careful explication of the quantitative re-expression of coefficients from these various models is excellent."—Contemporary Sociology"An extremely well-written book that will certainly prove an invaluable acquisition to the practicing statistician who finds other literature on analysis of discrete data hard to follow or heavily theoretical."—The StatisticianIn this revised and updated edition of their popular book, David Hosmer and Stanley Lemeshow continue to provide an amazingly accessible introduction to the logistic regression model while incorporating advances of the last decade, including a variety of software packages for the analysis of data sets. Hosmer and Lemeshow extend the discussion from biostatistics and epidemiology to cutting-edge applications in data mining and machine learning, guiding readers step-by-step through the use of modeling techniques for dichotomous data in diverse fields. Ample new topics and expanded discussions of existing material are accompanied by a wealth of real-world examples-with extensive data sets available over the Internet.
How different are insights based on cross-sectional studies from those of longitudinal investigations? We addressed this question using a detailed case study encompassing a rare suite of inter-connected cross-sectional and longitudinal investigations that have spanned the past two decades and included work on: (1) the decay and collapse of large-cavity forest trees (termed "trees with hollows"), (2) populations of a suite of species of arboreal marsupials that are reliant on trees with hollows as nesting and denning sites, and (3) relationships between the abundance, type, and condition of trees with hollows and the presence, abundance, and species richness of these animals. Our case study was from the montane ash eucalypt forests of the Central Highlands of Victoria, southeastern Australia. Our longitudinal studies led to new insights that either would not have been possible from a cross-sectional study, or which were unexpected because they did not conform, or only partially conformed, to postulated responses made at the outset based on the results of earlier research. These new insights included: (1) a substantial slowing in rates of tree fall between 1997 and 2006, which were significantly lower than predicted from earlier data gathered between 1983 and 1993, (2) no evidence for a decline in populations of almost all species of arboreal marsupials between 1997 and 2007, despite the loss of nearly 14% of the measured population of trees with hollows during that time, (3) changes in nest tree selection by some species of arboreal marsupials in response to these changes in hollow availability, (4) concentration effects, in which populations of animals used the declining tree hollow resource more intensively, and (5) evidence for significant rainfall effects on temporal changes in animal abundance. Our case study underscored the additional ecological insights that can be generated from longitudinal studies, including how relationships between biota and their habitat can change over time. Understanding these temporal changes is essential for informed forest management and biodiversity conservation, and points toward the need for greater use of longitudinal data sets in ecology.
Cavity nesting birds invest considerable time and effort into the construction of nests. The investment can be particularly high for species such as the black woodpecker (Dryocopus martius) that selects living trees as nest substrates. However, the investment may be reduced if fungal rot is present to help soften the wood. We used Resistograph drills to objectively assess fungal decay and tested whether black woodpeckers preferred trees with heart rot as sites for cavity starts. In doing so we also examined the distribution of fungal decay across the tree radius, analysed location of cavity starts with respect to proximity to heart rot, and evaluated wood condition at fresh and old cavity starts. Heart rot was significantly more common in beeches (Fagus sylvatica) with cavity starts than in random reference beeches. Fungal decay was not evenly distributed across the tree radius, but was more prevalent both in the central and outer thirds than in the middle third. Distance to heart rot was smaller from cavity starts than from random drills, suggesting a preference to initiate cavities close to heart rot. Wood density at fresh cavity starts was significantly higher than at old cavity starts. Collectively, these findings imply that black woodpeckers prefer to excavate cavity starts in beeches with heart rot, which the woodpeckers can detect based on cues unavailable to humans. The decay is reducing the energy expenditure of the black woodpecker and is a part of the long time excavation strategy. The cavity starts are an important factor in the process of excavating the large black woodpecker cavities in beech that enhance biodiversity in managed forests. Future studies should attempt to uncover the mechanisms woodpeckers use in selecting the locations of cavity starts.
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.
Higher densities of tree microhabitats in unmanaged forests may explain biodiversity differences with managed forests. To better understand the determinants of this potential biodiversity indicator, we studied the influence of tree characteristics on a set of tree microhabitats (e.g. cavities, cracks, bark features) on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality and species. We show that unmanaged forests contained more trees likely to host microhabitats (i.e. large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (e.g. veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.
Some habitat resources provided by trees take longer to form than the period between harvesting events in forests managed for wood production. In response, governments and forest certification schemes often prescribe that old trees must be retained in harvested stands. Despite these prescriptions there is evidence from around the world that structures provided by old trees have declined over successive harvesting events in wood production forests. This undermines the ecological sustainability of harvesting from natural forests and hinders the certification of wood products derived from them. What strategies are effective for perpetuating structures provided by old trees in harvested stands? We addressed this question using the retention of trees with hollows (or cavities) in the forests of south-eastern Australia—which take >120–220 years to develop—as a case study. We developed a simulation model populated with comprehensive data from these forests to simulate existing harvesting and a range of alternative management scenarios. We predicted that, under existing practice, only 35–79% of the intended numbers of hollow-bearing trees will be perpetuated. In a sensitivity analysis we found that 75% of the variation in predicted numbers of trees with hollows over multiple harvesting rotations could be explained by the number of recruitment trees retained for each hollow-bearing tree, the rate of mortality among retained trees, the length of the harvesting rotation and the rate at which trees developed hollows. Our results indicated that trees with hollows can only be perpetuated in harvested stands over multiple harvesting rotations if ≥2 recruitment trees are retained for each hollow-bearing tree and measures are employed to minimise mortality among all retained trees. Accelerating the development of old features in trees is beneficial. Managing stands on a long rotation (200 years) is only beneficial where mortality is unavoidably high. Predicting how many old trees will be perpetuated in harvested stands over multiple rotations is not a trivial exercise because of the number of variables that influence the outcome, uncertainty around some of these and the time-lag between putting strategies in place and observing their effects. Prescriptions for retaining structures provided by old trees in harvested stands can only be developed or audited if each of these issues is considered. We present a methodology that explicitly does this.
THE MOST PRACTICAL, UP-TO-DATE GUIDE TO MODELLING AND ANALYZING TIME-TO-EVENT DATANOW IN A VALUABLE NEW EDITION Since publication of the first edition nearly a decade ago, analyses using time-to-event methods have increase considerably in all areas of scientific inquiry mainly as a result of model-building methods available in modern statistical software packages. However, there has been minimal coverage in the available literature to9 guide researchers, practitioners, and students who wish to apply these methods to health-related areas of study. Applied Survival Analysis, Second Edition provides a comprehensive and up-to-date introduction to regression modeling for time-to-event data in medical, epidemiological, biostatistical, and other health-related research. This book places a unique emphasis on the practical and contemporary applications of regression modeling rather than the mathematical theory. It offers a clear and accessible presentation of modern modeling techniques supplemented with real-world examples and case studies. Key topics covered include: variable selection, identification of the scale of continuous covariates, the role of interactions in the model, assessment of fit and model assumptions, regression diagnostics, recurrent event models, frailty models, additive models, competing risk models, and missing data. Features of the Second Edition include: Expanded coverage of interactions and the covariate-adjusted survival functions The use of the Worchester Heart Attack Study as the main modeling data set for illustrating discussed concepts and techniques New discussion of variable selection with multivariable fractional polynomials Further exploration of time-varying covariates, complex with examples Additional treatment of the exponential, Weibull, and log-logistic parametric regression models Increased emphasis on interpreting and using results as well as utilizing multiple imputation methods to analyze data with missing values New examples and exercises at the end of each chapter Analyses throughout the text are performed using Stata Version 9, and an accompanying FTP site contains the data sets used in the book. Applied Survival Analysis, Second Edition is an ideal book for graduate-level courses in biostatistics, statistics, and epidemiologic methods. It also serves as a valuable reference for practitioners and researchers in any health-related field or for professionals in insurance and government.
Approximately 85% of the global forest estate is neither formally protected nor in areas dedicated to intensive wood production (e.g., plantations). Given the spatial extent of unprotected forests, finding management approaches that will sustain their multiple environmental, economic, and cultural values and prevent their conversion to other uses is imperative. The major global challenge of native forest management is further demonstrated by ongoing steep declines in forest biodiversity and carbon stocks. Here, we suggest that an essential part of such management—supplementing the protection of large reserves and sensitive areas within forest landscapes (e.g., aquatic features)—is the adoption of the retention approach in forests where logging occurs. This ecological approach to harvesting provides for permanent retention of important selected structures (e.g., trees and decayed logs) to provide for continuity of ecosystem structure, function, and species composition in the postharvest forest. The retention approach supports the integration of environmental, economic, and cultural values and is broadly applicable to tropical, temperate, and boreal forests, adaptable to different management objectives, and appropriate in different societal settings. The widespread adoption of the retention approach would be one of the most significant changes in management practice since the onset of modern high-yield forestry.
The majority of the world's forests are used for multiple purposes, which often include the potentially conflicting goals
of timber production and biodiversity conservation. A scientifically validated management approach that can reduce such conflicts
is retention forestry, an approach modeled on natural processes, which emerged in the last 25 years as an alternative to clearcutting.
A portion of the original stand is left unlogged to maintain the continuity of structural and compositional diversity. We
detail retention forestry's ecological role, review its current practices, and summarize the large research base on the subject.
Retention forestry is applicable to all forest biomes, complements conservation in reserves, and represents bottom-up conservation
through forest manager involvement. A research challenge is to identify thresholds for retention amounts to achieve desired
outcomes. We define key issues for future development and link retention forestry with land-zoning allocation at various scales,
expanding its uses to forest restoration and the management of uneven-age forests.
It is argued that the development of decay in living hardwoods can best be explained in terms of the unsuitability of functional sapwood for mycelial establishment owing to its high moisture content and lack of easily assimilable nutrients other than within living cells. Decay occurs when these limitations are removed by any mechanisms which prevent or interfere with the normal functioning of sapwood. Recent concepts of decay in living trees have implied an active host defence against infection. This view is discussed against the alternative that non-specific mechanisms which maintain sapwood function will, by their very nature, prevent establishment of -ycelium of decay and stain fungi. The significance of mixed microbial communities in the development of decay is discussed, particularly in relation to the supposed requirement for specific sequences to overcome host defences.
