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Importance of conserving large and old trees to continuity of tree‐related microhabitats

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Conservation Biology
Authors:
Daniel Kozák at Czech University of Life Sciences Prague
Daniel Kozák
Marek Svitok at Technical University of Zvolen
Marek Svitok
Veronika Zemlerová at Czech University of Life Sciences Prague
Veronika Zemlerová
Martin Mikoláš at Czech University of Life Sciences Prague
Martin Mikoláš
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Abstract and Figures

Protecting structural features, such as tree‐related microhabitats (TreMs), is a cost‐effective tool crucial for biodiversity conservation applicable to large forested landscapes. Although 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. Although many TreM groups were positively associated with tree age and diameter, only two 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 a 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 the 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.
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Received: 28 February 2022 Revised: 19 October 2022 Accepted: 15 November 2022
DOI: 10.1111/cobi.14066
CONTRIBUTED PAPERS
Importance of conserving large and old trees to continuity of
tree-related microhabitats
Daniel Kozák1,#Marek Svitok1,2,#Veronika Zemlerová1Martin Mikoláš1
Thibault Lachat3Laurent Larrieu4Yoan Paillet5Arne Buechling1Radek Baˇ
ce1
William S. Keeton6Lucie Vítková1Krešimir Begoviˇ
c1Vojt ˇ
ech ˇ
Cada1
Martin Dušátko1Matej Ferenˇ
cík1Michal Frankoviˇ
c1Rhiannon Gloor1
Je ˇ
nýk Hofmeister1Pavel Janda1Ondrej Kameniar1Tomáš Kníˇ
r1
Linda Majdanová1Marek Mejstˇ
rík1Jakob Pavlin1Dheeraj Ralhan1
Ruffy Rodrigo1Catalin-Constantin Roibu7Michal Synek1Ondˇ
rej Vostarek1
Miroslav Svoboda1
1Department of Forest Ecology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic
2Department of Biology and General Ecology, Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, Zvolen, Slovakia
3Bern University of Applied Sciences, School of Agricultural, Forest and Food Sciences HAFL, Zollikofen & Swiss Federal Institute for Forest, Snow and Landscape Research WSL,
Birmensdorf, Switzerland
4Université de Toulouse, INRAE, UMR DYNAFOR, Castanet-Tolosan, France & CNPF-CRPF Occitanie, Tarbes, France
5Univ. Grenoble Alpes, INRAE, UR Lessem, Lessem, France
6University of Vermont, Rubenstein School of Environment and Natural Resources, Burlington, Vermont, USA
7Forest Biometrics Laboratory–Faculty of Forestry, ‘Stefan cel Mare’ University of Suceava, Suceava, Romania
Correspondence
Daniel Kozák, Department of Forest Ecology,
Faculty of Forestry and Wood Sciences, Czech
University of Life Sciences Prague, Prague, Czech
Republic.
Email: kozakd@fld.czu.cz
Article Impact Statement: Conservation of habitat
trees based on size, without considering tree age,
may impair landscape-level biodiversity potential.
Funding information
Grantová Agentura ˇ
Ceské Republiky, Grant/Award
Number: 22-31322S; European Regional
Development Fund, Grant/Award Number:
ITMS313011T721; Ministerstvo Školství, Mládeže
a Telovýchovy, Grant/Award Number:
CZ.02.1.01/0.0/0.0/16_019/0000803
Abstract
Protecting structural features, such as tree-related microhabitats (TreMs), is a cost-effective
tool crucial for biodiversity conservation applicable to large forested landscapes. Although
the development of TreMs is influenced by tree diameter, species, and vitality, the relation-
ships 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, diam-
eter, 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 for-
est 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. Although many TreM groups were positively associated
with tree age and diameter, only two 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 a 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
#These authors contributed equally to this work.
Conservation Biology. 2023;37:e14066. © 2023 Society for Conservation Biology. 1of12wileyonlinelibrary.com/journal/cobi
https://doi.org/10.1111/cobi.14066
... Forests support associated biodiversity and socio-economic interests (Norman et al., 2010;Aerts and Honnay 2011;Götmark 2013;Löf et al. 2016;Piovesan et al. 2022;Kozák et al. 2023;Forsman et al. 2024), and are key components in global policy-making to mitigate climate change, as a complement to reducing anthropogenic carbon emissions (Vieira et al. 2005;Stephenson et al. 2014;Friedlingstein et al. 2022;Peng et al. 2023;Roebroek et al. 2023). Old forests are considered pinnacles of biodiversity, as larger and older trees provide structural complexity, accumulate more niches, and tend to support a greater diversity of species (Piovesan et al. 2022;Kozák et al. 2023;Storch et al. 2023;Zeller et al. 2023). ...
... Forests support associated biodiversity and socio-economic interests (Norman et al., 2010;Aerts and Honnay 2011;Götmark 2013;Löf et al. 2016;Piovesan et al. 2022;Kozák et al. 2023;Forsman et al. 2024), and are key components in global policy-making to mitigate climate change, as a complement to reducing anthropogenic carbon emissions (Vieira et al. 2005;Stephenson et al. 2014;Friedlingstein et al. 2022;Peng et al. 2023;Roebroek et al. 2023). Old forests are considered pinnacles of biodiversity, as larger and older trees provide structural complexity, accumulate more niches, and tend to support a greater diversity of species (Piovesan et al. 2022;Kozák et al. 2023;Storch et al. 2023;Zeller et al. 2023). In principle, large trees should have the potential to contribute disproportionately to biomass increment, due to the allometric scaling that amplifies linear growth in stem diameter to a volume increase (e.g., Stephenson et al. 2014, Pretzsch 2020, Zhou et al. 2021). ...
... The benefits of old and large trees extend beyond any positive effects that their continued high capacity for biomass accumulation may have for carbon sequestration. From an ecological perspective, old forests support a greater number and diversity of associated species (Piovesan et al. 2022;Kozák et al. 2023;Storch et al. 2023;Zeller et al. 2023). Mixed-species forests also come with ecological advantages over monocultures in terms of productivity and resistance to environmental stressors (e.g., Zhang et al. 2012, Pretzsch et al. 2013, Tilman et al. 2014). ...
View
... Tree age was the main driver of the diversity of TreM types and groups on retention trees. To our knowledge, there is only one previous study (Kozák et al., 2023) that analyzed the relationship between tree age and TreM occurrence and diversity. We observed that as tree age increased, the overall diversity of TreM types significantly increased, as well as the occurrence of some TreM groups, including rot holes, crown deadwood, exposed sapwood only and exposed sap-and heartwood. ...
... We observed that as tree age increased, the overall diversity of TreM types significantly increased, as well as the occurrence of some TreM groups, including rot holes, crown deadwood, exposed sapwood only and exposed sap-and heartwood. This can be explained by the longer time frame needed to develop these groups of TreMs and the increasing susceptibility of individual trees to the age-related abiotic and biotic damages that underlie their formation (Kozák et al., 2023). Crown deadwood is a TreM strongly associated with ontogenic stages of maturity and senescence , whereas rot holes originate from bark losses. ...
... It is likely that the use of skidders and other equipment during logging promoted the bark lost in the retained trees first, which later derived into the observed rot holes through a saproxylation process that can take between 10 and 20 years just to reach a first stage in the cavity development, depending on tree species, fungi, and insects that colonize the bark. As a result, the older the trees are, the more likely they are to create these slow-developing TreMs (Fritz et al., 2009;Kozák et al., 2023;Ranius et al., 2009). ...
Tree and stand characteristics jointly predict tree-related microhabitats on retention trees in production forests
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  • Oct 2024
  • BIOL CONSERV
Retention forestry emerged as a means of ameliorating the biodiversity impacts of clearcutting 30 years ago and has become an integrated part of forest management in many countries. Nowadays, there is still an increasing need to assess to what extent retention trees contribute to biodiversity in production forests. We used tree-related microhabitats (TreMs), as an indicator of the potential of the forest to host taxonomic biodiversity, to better understand the effect of broadleaf retention trees, and surrounding conditions derived from stand management, on biodiversity. We inventoried TreM types on 114 retention trees of four broadleaf tree taxa (Betula spp., Fagus sylvatica, Quercus spp., and Populus tremula) located within 20 even-aged conifer-dominated production forests (Picea abies) in southern Sweden. We evaluated the effect of retention tree attributes (species and age) and of the surrounding environment (production tree density and distance to the retained trees) on the diversity of TreM types and groups. We found that retention tree species with different characteristics and physiological niche (light-demanding vs. shade-tolerant and pioneer vs. late-successional) developed distinct TreM assemblages. TreM diversity increased significantly with increasing retention tree age and surrounding tree density. Higher surrounding tree density is particularly related to some TreMs either positively (crown deadwood, bryophytes) or negatively (buttress-root concavities, lichens). Overall, the extent that retention forestry potentially contributes to forest biodiversity will depend on promoting different broadleaved retention tree species and managing surrounding trees accordingly to allow retention trees to become older and maintain TreMs in the long term.
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... The spatial variance of TreMs occurrence rate could partially stem from the fact that TreM occurrence rate was quantified as a function of tree diameter but overlooked tree age, which is harder to obtain on a large scale basis. Tree diameter being kept constant, many TreM types are known to occur more often on older trees [Kozák et al., 2023]. Therefore any variation in tree growth speed (e.g. ...
... Because the DBH of a tree also increases in time, one expects a positive correlation between DBH and basal rot-hole occurrence. The absence of relationship between DBH and basal rot-hole occurrence in the model calibrated with non-informative priors was therefore surprising and at variance with previous studies [Courbaud et al., 2017, 2022, Kozák et al., 2023. Our result suggested that tree holes would not develop slowly with tree growth, but rather appear on a random fraction of trees before they reach the 17.5 cm DBH threshold at which our observations started. ...
Large-scale informative priors to better predict the local occurrence rate of a rare tree-related microhabitat
Preprint
Full-text available
  • Dec 2024
Ecological processes associated to rare events are hard to estimate from individual empirical studies. A typical example in forest ecology is the formation of tree-related microhabitats (TreMs) on trees. TreMs are key features for forest biodiversity, and their accumulation rate is a key information to design integrative management strategies. Many types of TreMs are associated to large old trees and show slow ontogenical processes. The rarity of such TreMs (particularly in intensively managed forests) hinder the estimation of their occurrence rate along tree growth. Several meta-analyses accumulated data on TreMs at continental (e.g. european) scale. However, using data accumulated at these large, heterogeneous scales to orientate management wihtin a specific site remains challenging. Here, we used a large-scale meta-analysis on TreMs occurrence rate along tree growth to build informative priors for a model of basal rot-hole occurrence on oaks within the Grésigne forest, France. We found that calibrating a model without the prior information (i.e. using only Grésigne oak trees) did not reveal any increase of occurrence with tree diameter. Estimation was hindered by confounding effects of plot and tree diameter induced by the local plot-based sampling strategy. Informative priors overcame this confounding effect, restored a positive relationship between diameter and basal rot-hole occurrence but raised the question of whether it introduced biases. A separate validation experiment suggested that it did not. The model with informative priors revealed that the high recruitment of basal rot-holes in Grésigne may be a temporary management effect in stands undergoing conversion from coppice-with-standards to high forest through sprout thinning, which will lead to conservation issues for cavicolous saproxylic species when all conversions are complete. Because using informative priors was simple and beneficial in our study, it should be further explored in other local applied contexts to orientate forest management.
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... It should be emphasized that the DBH > 50 cm class is only available for living trees among the indicators included in this study. Many studies have found that large-diameter mature trees are good predictors of higher microhabitat diversity [58][59][60][61]. The taxa we studied also showed a strong correlation with the average number of large trees. ...
Relationships Between Saproxylic Beetle Microhabitat Occurrences and Forest State Indicators
Article
Full-text available
  • Jan 2025
The use of proxies in habitat assessments has become widespread in recent decades. We used forest state descriptive data from a large-scale project (SCP) as proxies to investigate the occurrence of habitats suitable for some protected saproxylic beetles. We searched for pre-defined tree-related microhabitats (TreMs) suitable for saproxylic beetles in 1 ha quadrats in the Börzsöny Mts., Hungary. We compared the frequency of each microhabitat type with the aggregated values of the forest state proxies. Our results suggest that the average number of snags with DBH = 21-50 cm and the frequency of lying deadwood with Ø > 35 cm can adequately represent the occurrence of all beetle microhabitats studied. In most cases, the frequency of plots with species richness of live canopy trees with DBH > 35 cm and the amount of lying dead wood were also good indicators. The TreM indicators of the SCP alone can detect the presence of specialist beetles requiring cavities. The stands with a better forest state had more protected saproxylic beetles. The practical implementation of our work is based on the optimization of the resources required for monitoring. In surveys prepared to cover large areas, it is easier to monitor the habitat of saproxylic beetles with the help of individual proxies.
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... Moreover, older trees likely host standing deadwood such as dead branches, or rotten areas where cavities are more likely to form naturally (Larrieu et al., 2018). This has important implications in terms of conservation and forestry management, as it underlines the importance of large veteran trees as hotspots of biodiversity (Kozák et al., 2023;Lindenmayer 2017). Our findings demonstrate that DBH is a cost-effective indicator to measure TReM diversity in forests. ...
Variation in the diversity and composition of tree-related microhabitats across climate and human impact gradients on a tropical mountain
Article
Full-text available
  • Nov 2024
  • ECOL INDIC
Tree-related microhabitats (TReMs) have been proposed as important indicators of biodiversity to guide forest management. However, their application has been limited mostly to temperate ecosystems, and it is largely unknown how the diversity of TReMs varies along environmental gradients. In this study, we assessed the diversity of TReMs on 180 individual trees and 44 plots alongside a large environmental gradient on Kilimanjaro, Tanzania. We used a typology adjusted to tropical ecosystems and a tree-climbing protocol to obtain quantitative information on TreMs on large trees and dense canopies. We computed the diversity of TReMs for each individual tree and plot and tested how TReM diversity was associated with properties of individual trees and environmental conditions in terms of climate and human impact. We further used non-metric multidimensional scaling (NMDS) to investigate the composition of TReM assemblages alongside the environmental gradients. We found that diameter at breast height (DBH) and height of the first branch were the most important determinants of TReM diversity on individual trees, with higher DBH and lower first branch height promoting TReM diversity. At the plot level, we found that TReM diversity increased with mean annual temperature and decreased with human impact. The composition of TReMs showed high turnover across ecosystem types, with a stark difference between forest and non-forest ecosystems. Climate and the intensity of human impact were associated with TReM composition. Our study is a first test of how TReM diversity and composition vary along environmental gradients in tropical ecosystems. The importance of tree size and architecture in fostering microhabitat diversity underlines the importance of large veteran trees in tropical ecosystems. Because diversity and composition of TReMs are sensitive to climate and land-use effects, our study suggests that TReMs can be used to efficiently monitor consequences of global change for tropical biodiversity.
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... Further, intensive logging reduces the amount of large and old trees that are typically more structurally diverse with coarse bark, holes and cavities. These are important for a diverse group of taxa, such as epiphytic lichens and bryophytes, invertebrates and birds (Hämäläinen et al., 2023;Kozák et al., 2023). Meanwhile, natural disturbance dynamics lead to multilayered tree canopies, which have a patchy distribution of trees in several age classes (Kuuluvainen, 2016). ...
Long term effects of forest management on forest structure and dead wood in mature boreal forests
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Full-text available
  • Oct 2024
  • FOREST ECOL MANAG
The history of forestry in Fennoscandia spans five centuries, with clear-cutting being the dominant practice since the mid-20th century. This has led to a significant transformation of the forest landscape. In this study we investigated long-term effects of clear-cutting on forest structure and dead wood volumes. We established twelve pairs of spruce forest sites in southeastern Norway, each pair constituting of a mature, previously clear-cut stand and its near-natural counterpart with similar edaphic factors. The near-natural stands had 2.8 times higher volumes of dead wood and a larger proportion of dead wood in late stages of decay. The near-natural stands had on average 36.8 ± 9.1 m 3 ha − 1 of downed dead wood and 24.1 ± 6.2 m 3 ha − 1 of standing dead wood. Corresponding numbers for the previously clear-cut stands were 10.2 ± 2.8 m 3 ha − 1 and 11.9 ± 3.7 m 3 ha − 1. Forests with lower volumes of dead wood often also had lower connectivity of old spruce forests, which potentially have further negative effects on biodiversity. Furthermore, near-natural stands displayed greater tree size heteroge-neity, resulting in a wider variation in light conditions. While no difference was observed in living tree volume, we found only weak evidence for higher basal area in the previously clear-cut stands, which had a higher stem density with more slender stems and shorter crowns. Our findings suggest that managed forests do not develop structures typical of near-natural forests before they become mature for logging. We stress the importance of a thorough site selection for studies of management effects, as forest management history may be confounded with productivity and other edaphic factors. Experimental designs like ours are vital for testing how differences in structure and deadwood volumes, driven by forest management, translate into variations in biodiversity, carbon sequestration and ecosystem functioning in future studies.
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... To maintain the bryophyte diversity in intensively managed forests, we recommend, at least in part of the territory, appropriate methods of forest management, including planting broad-leaved stands with an appropriate area and an adequate combination of native trees, e.g., the genera Quercus, Fraxinus, Ulmus, Acer, and Tilia. Furthermore, we suggest protecting old specimens of trees as a source of microhabitats for various groups of organisms (Mežaka et al. 2012;Kozák et al. 2023) and maintaining forest retention patches for hemerophobic bryophytes. Recently, coniferous stands with Pinus sylvestris have been planted on sandy, nutrient-poor dry soil. ...
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The majority of the woodland area in Central Europe is composed of managed forests. Although the species diversity and composition, particularly in older forests, may be similar to those of natural or close-to-nature forests, intensive forestry and other human activities have adverse impacts on biodiversity. The present study focused on bryophyte diversity in managed lowland forests, as these have received less attention compared to other types of forests. Our research targeted the area located within the Borská nížina Lowland in south-western Slovakia. In total, 37 forest sampling plots (SPs) were selected, representing five different forest types, namely Quercus, Fraxinus, Robinia, Pinus, and mixed forests. Multivariate statistical analyses were conducted across these forest types to demonstrate variations in bryophyte species richness, composition, and functional traits. Overall, 60 species of bryophytes were identified, of which five were liverworts and 55 were mosses. Epiphytes were the most abundant substrate group in deciduous and mixed stands, while epigeic species prevailed in Pinus forests. Considering environmental factors, the bryophyte diversity was influenced mostly by the forest type and area size of SPs. Clear differences in species composition were observed when comparing coniferous and deciduous stands, as well as non-native Robinia forests and native tree stands. Overall, intensive forest management results in a high concentration of hemerophilous and nitrophilous species, along with the absence of rare and threatened mosses and liverworts. Nevertheless, by adhering to proper management methods, even managed forests can provide suitable habitats for various bryophytes.
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Article
  • Jan 2025
  • SCI TOTAL ENVIRON
Tree-related Microhabitats (TreMs) are essential for sustaining forest biodiversity. Although TreMs represent ephemeral resources that are spread across the landscape, their spatial distribution within temperate forests remains poorly understood. To address this knowledge gap, we conducted a study on 90 sample plots (0.05 ha each) located in a primeval mountain European beech Fagus sylvatica-dominated forest (Bieszczady Mountains, Carpathians). We explored the TreM profile with its link to habitat characteristics and described the spatial distribution of TreM indices. We identified 61 TreM types, with a mean richness of 19.7 ± 4.9 SD TreM types per plot, a mean density of 740.7 ± 292.5 SD TreM-bearing trees ha−1 and a mean TreM diversity of 1.2 ± 0.1 SD. The diameter and living status of trees (living vs dead standing tree) were correlated with TreM richness on an individual tree. The stand structure, i.e. density and/or basal area of living and/or dead standing trees, and topographic conditions, i.e. slope exposure, were correlated with the TreM richness, density and diversity recorded on a study plot. We found no relationship between TreM richness, density and diversity and the presence of canopy gaps, which indicates that the influence of small-scale disturbances on the TreM profile is limited. However, our analysis revealed a clustered spatial pattern of TreM indices, with TreM-rich habitat patches (hot-spots) covering ~20 % of the forest. A moderate TreM richness, density and diversity dominated ~60 % of the forest, while TreM-poor habitat patches (cold-spots) covered ~20 %. Based on our findings, we advise the transfer of knowledge on the spatial distribution of TreMs from primeval to managed forests and advocate the ‘2:6:2’ triad rule: to allocate 20 % of forests as strictly protected areas, to dedicate 60 % to low-intensity forest management with the retention of large living trees and all dead standing trees, and to use the remaining 20 % for intensive timber production. To ensure the continuance of the majority of TreM types, ≥55 living trees ha−1 >60 cm in diameter should be retained. Such an approach will maintain a rich and diverse TreM assemblage across a broad spatial scale, which in turn will support biodiversity conservation and ecosystem restoration in secondary or managed forests.
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Forest Biodiversity in Europe
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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.
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Old trees are important for biodiversity, and the process of their identification is a critical process in their conservation. However, determining the tree age by core extraction, ring counts, and eventually, cross-dating by means of dendrochronology is labor-intensive and expensive. Here we examine the alternative method of estimating determining tree age by visual characteristics for old Norway spruce and Scots pine trees. We used forest stands previously identified as “Old tree habitats” by visual criteria in Norwegian boreal forests. The efficiency of this method was tested using pairwise comparison of the age of core samples from trees within these sites, and within neighboring sites. Age regression models were constructed from morphological traits and site variables to investigate how accurately old trees can be detected. Cored trees in the Old-tree habitats were on average 41.9 years older than compared to a similar selection of trees from nearby mature forests. Several characteristics such as bark structure, stem taper and visible growth eccentricities can be used to identify old Norway spruce and Scots pine trees. Old trees were often found on less productive sites. Due to the wide range of environments included in the study, we suggest that these findings can be generalized to other parts of the boreal zone.
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Factors influencing the rate of formation of tree‐related microhabitats and implications for biodiversity conservation and forest management
Article
Full-text available
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.
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European primary forest database v2.0
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Full-text available
  • Aug 2021
Primary forests, defined here as forests where the signs of human impacts, if any, are strongly blurred due to decades without forest management, are scarce in Europe and continue to disappear. Despite these losses, we know little about where these forests occur. Here, we present a comprehensive geodatabase and map of Europe’s known primary forests. Our geodatabase harmonizes 48 different, mostly field-based datasets of primary forests, and contains 18,411 individual patches (41.1 Mha) spread across 33 countries. When available, we provide information on each patch (name, location, naturalness, extent and dominant tree species) and the surrounding landscape (biogeographical regions, protection status, potential natural vegetation, current forest extent). Using Landsat satellite-image time series (1985–2018) we checked each patch for possible disturbance events since primary forests were identified, resulting in 94% of patches free of significant disturbances in the last 30 years. Although knowledge gaps remain, ours is the most comprehensive dataset on primary forests in Europe, and will be useful for ecological studies, and conservation planning to safeguard these unique forests.
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Tree-Related Microhabitats Follow Similar Patterns but are More Diverse in Primary Compared to Managed Temperate Mountain Forests
Article
Full-text available
  • Apr 2022
  • ECOSYSTEMS
The impact of forest management on biodiversity is difficult to scrutinize along gradients of management. A step towards analyzing the impact of forest management on biodiversity is comparisons between managed and primary forests. The standardized typology of tree-related microhabitats (TreMs) is a multi-taxon indicator used to quantify forest biodiversity. We aim to analyze the influence of environmental factors on the occurrence of groups of TreMs by comparing primary and managed forests. We collected data for the managed forests in the Black Forest (Germany) and for the primary forests in the Western (Slovakia) and Southern Carpathians (Romania). To model the richness and the different groups of TreMs per tree, we used generalized linear mixed models with diameter at breast height (DBH), altitude, slope and aspect as predictors for European beech ( Fagus sylvatica (L.)) , Norway spruce ( Picea abies (L.) ) and silver fir ( Abies alba (Mill.) ) in primary and managed temperate mountain forests. We found congruent results for overall richness and the vast majority of TreM groups. Trees in primary forests hosted a greater richness of all and specific types of TreMs than individuals in managed forests. The main drivers of TreMs are DBH and altitude, while slope and aspect play a minor role. We recommend forest and nature conservation managers to focus: 1) on the conservation of remaining primary forests and 2) approaches of biodiversity-oriented forest management on the selection of high-quality habitat trees that already provide a high number of TreMs in managed forests based on the comparison with primary forests.
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Disturbance history is a key driver of tree lifespan in temperate primary forests
Article
Full-text available
  • Aug 2021
Aims We examined differences in lifespan among the dominant tree species (spruce (Picea abies (L.) H. Karst.), fir (Abies alba Mill.), beech (Fagus sylvatica L.), and maple (Acer pseudoplatanus L.)) across primary mountain forests of Europe. We ask how disturbance history, lifetime growth patterns, and environmental factors influence lifespan. Locations Balkan mountains, Carpathian mountains, Dinaric mountains. Methods Annual ring widths from 20,600 cores from primary forests were used to estimate tree life spans, growth trends, and disturbance history metrics. Mixed models were used to examine species-specific differences in lifespan (i.e. defined as species-specific 90th percentiles of age distributions), and how metrics of radial growth, disturbance parameters, and selected environmental factors influence lifespan. Results While only a few beech trees surpassed 500 years, individuals of all four species were older than 400 years. There were significant differences in lifespan among the four species (beech > fir > spruce > maple), indicating life history differentiation in lifespan. Trees were less likely to reach old age in areas affected by more severe disturbance events, whereas individuals that experienced periods of slow growth and multiple episodes of suppression and release were more likely to reach old age. Aside from a weak but significant negative effect of vegetation season temperature on fir and maple lifespan, no other environmental factors included in the analysis influenced lifespan. Conclusions Our results indicate species-specific biological differences in lifespan, which may play a role in facilitating tree species coexistence in mixed temperate forests. Finally, natural disturbances regimes were a key driver of lifespan, which could have implications for forest dynamics if regimes shift under global change.
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Tree-related microhabitats on live Populus tremula and Picea abies in relation to tree age, diameter, and stand factors in Estonia
Article
Full-text available
  • Oct 2021
  • EUR J FOREST RES
Production forestry is known to reduce the naturally variable microhabitat pools in live trees and their biodiversity by tree removal and broad indirect effects of silviculture. However, the tree-scale processes are not known well enough for microhabitat management for the future. This study investigates how tree age affects the microhabitat occurrence in live trees, its effect modifiers, and explanatory value compared with tree diameter. We inventoried tree-related microhabitats on 879 live aspens (Populus tremula) and Norway spruces (Picea abies) of known age in 141 forests representing contrasting productive site conditions in Estonia. We analysed microhabitat incidence using logistic mixed models for significant tree-scale and stand-scale factors. Most microhabitat types appeared rare even in old trees, and the age effects had various patterns. Only 2% of trees bore five or more microhabitat types. Aspens and spruces had a similar microhabitat diversity before 80 years of age. Stand-level effects varied among microhabitat types but were less significant than tree-level effects; interactions were even rarer. Most effects found could be interpreted through known ecological processes; for example, humidity-dependent epiphytic growth; bark stripping by herbivores; pathogen effects in forests with distinct histories. In contrast, a reliable tree-scale prediction of microhabitat occurrence appears rarely possible; and depending on microhabitat type, either tree age or diameter can be a better predictor. We suggest that managing for tree-related microhabitats in production forests should combine facilitating ecological conditions for microhabitat formation, and early detection and retention of the trees with high microhabitat potential.
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Co-occurrence patterns of tree-related microhabitats: A method to simplify routine monitoring
Article
Full-text available
  • May 2021
  • ECOL INDIC
A Tree-related Microhabitat (TreM) is a distinct, well-delineated morphological singularity occurring on living or standing dead trees, which constitutes a crucial substrate or life site for various species. TreMs are widely recognized as key features for biodiversity. Current TreM typology identifies 47 TreM types according to their morphology and their associated taxa. In order to provide a range of resolutions and make the typology more user-friendly, these 47 TreM types have been pooled into 15 groups and seven forms. Depending on the accuracy required and the time available, a user can now choose to describe TreMs at resolution levels corresponding to type, group or form. Another way to more easily record TreMs during routine management work would be to use co-occurrence patterns to reduce the number of observed TreMs required. Based on a large international TreM database (2052 plots; 70,958 individual trees; 78 tree species), we evaluated both the significance and the magnitude of TreM co-occurrence on living trees for 11 TreM groups. We highlighted 33 significant co-occurrences for broadleaves and nine for conifers. Bark loss, rot hole, crack and polypore had the highest number of positive co-occurrences (N = 8) with other TreMs on broadleaves; bark loss (N = 4) had the highest number for conifers. We found mutually exclusive occurrences only for conifers: Exposed Heartwood excluded both dendrotelm and sap run. Among the four variables we tested for their positive contribution to significant co-occurrences, tree diameter at breast height was the most consistent. Based on our results and practical considerations , we selected three TreM groups for broadleaves, and nine for conifers, and formed useful short lists to reduce the number of TreM groups to assess during routine forest management work in the field. In addition, detecting potential similarities or associations between TreMs has potential theoretical value, e.g. it may help researchers identify common factors favouring TreM formation or help managers select trees with multiple TreMs as candidates for retention.
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