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Abstract

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.

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... Furthermore, total wind-induced forest damage has increased since the early 20th century (Schelhaas et al., 2003;Seidl et al., 2017;Usbeck et al., 2010). Shifting disturbance dynamics and managerial responses to disturbance can alter habitat provisioning (Bengtsson et al., 2000;Kozák et al., 2018), regulate carbon storage (Burrascano et al., 2013;Carey et al., 2001;Harmon et al., 1990;Luyssaert et al., 2008;Seedre et al., 2020), and impact the role of forestry in the European economy (Leverkus et al., 2012;Müller et al., 2019). Thus, understanding the drivers of shifting wind disturbance patterns is needed to facilitate informed decision-making for forest and conservation management, and additionally quantify the future role of Europe's forests in global biogeochemical cycles. ...
... We assessed the historical disturbance of 20 beech-dominated primary mixed forests stands within the Carpathian Mountains of Slovakia and Romania. The presence of primary forests was determined through forest inventories in Slovakia (Kozák et al., 2018;Mikoláš et al., 2019;Sabatini et al., 2018; also see http:// remoteforests.org) and Romania (Kozák et al., 2018;Sabatini et al., 2018) and detailed descriptions of these primary forest inventories can be found in the study by Mikoláš et al., (2019). Primary forest stands occurred in four geographic clusters which we refer to as landscapes (West Slovakia, East Slovakia, North Romania, and South Romania) covering 42°-50° latitude and 14°-25° longitude, with plots ranging in elevation from 615 to 1,324 m a.s.l ( Figure 2a). ...
... We assessed the historical disturbance of 20 beech-dominated primary mixed forests stands within the Carpathian Mountains of Slovakia and Romania. The presence of primary forests was determined through forest inventories in Slovakia (Kozák et al., 2018;Mikoláš et al., 2019;Sabatini et al., 2018; also see http:// remoteforests.org) and Romania (Kozák et al., 2018;Sabatini et al., 2018) and detailed descriptions of these primary forest inventories can be found in the study by Mikoláš et al., (2019). Primary forest stands occurred in four geographic clusters which we refer to as landscapes (West Slovakia, East Slovakia, North Romania, and South Romania) covering 42°-50° latitude and 14°-25° longitude, with plots ranging in elevation from 615 to 1,324 m a.s.l ( Figure 2a). ...
Article
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Wind is the leading disturbance agent in European forests, and the magnitude of wind impacts on forest mortality has increased over recent decades. However, the atmospheric triggers behind severe winds in Western Europe (large‐scale cyclones) differ from those in Southeastern Europe (small‐scale convective instability). This geographic difference in wind drivers alters the spatial scale of resulting disturbances and potentially the sensitivity to climate change. Over the 20th century, the severity and prevalence of cyclone‐induced windstorms have increased while the prevalence of atmospheric instability has decreased and thus, the trajectory of Europe‐wide windthrow remains uncertain. To better predict forest sensitivity and trends of windthrow disturbance we used dendrochronological methods to reconstruct 140 years of disturbance history in beech‐dominated primary forests of Central and Eastern Europe. We compared generalized linear mixed models of these disturbance time series to determine whether large‐scale cyclones or small‐scale convective storms were more responsible for disturbance severity while also accounting for topography and stand character variables likely to influence windthrow susceptibility. More exposed forests, forests with a longer absence of disturbance, and forests lacking recent high severity disturbance showed increased sensitivity to both wind drivers. Large‐scale cyclone‐induced windstorms were the main driver of disturbance severity at both the plot and stand scale (0.1–∼100 ha) whereas convective instability effects were more localized (0.1 ha). Though the prevalence and severity of cyclone‐induced windstorms have increased over the 20 century, primary beech forests did not display an increase in the severity of windthrow observed over the same period.
... Most studies that have examined the influence of forest management on biodiversity habitat have overlooked microhabitats (Paillet et al., 2017;, yet there are an increasing number of studies that quantify them, mainly in managed forests or formerly managed forest reserves (e.g. Paillet et al., 2017;Vuidot et al., 2011;Winter et al., 2015;Winter and Möller, 2008;Regnery et al.;2013, Larrieu andCabanetes, 2012;Caurbaud et al., 2017;Bütler et al., 2013) and, to a lesser extent, in well preserved old-growth forests (Kozak et al., 2018;Larrieu et al., 2014;Michel and Winter, 2009). Taken together, these studies generally show a different profile of microhabitats between managed and unmanaged stands. ...
... bark loss) Vuidot et al., 2011). In contrast, old-growth forests have a high density of large old trees, which support a unique set of structures, including cavities, large broken branches from natural disturbance, and substantial accumulation of canopy deadwood (Kozak et al., 2018;Brunet et al., 2010). In Slovenia, many authors have highlighted the importance of habitat and dead trees for biodiversity. ...
... A key finding of many studies (and this study) is that standing dead trees (snags) host a large number and diversity of microhabitats (Vuidot et al., 2011;Kozak et al., 2018;Bull et al., 1997;. Given that large standing dead trees rarely develop or are routinely removed in managed forests, they lack a number of key microhabitats compared to unmanaged forest. ...
Article
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An inventory of tree microhabitats was done in two unmanaged forests (Kobile and Ravna gora forest reserves) and one managed beech forest in SE Slovenia. The purpose of this study was to determine the influence of forest management, natural disturbances, and tree characteristics on microhabitat patterns. Forest structure and microhabitats were recorded in systematically placed plots (500 m2 in size) across each area. In total, we inventoried 849 trees on 54 plots and 1833 tree microhabitats. The results showed that forest management had no significant influence on the abundance of microhabitats per tree, but there were differences regarding microhabitat type between managed and unmanaged sites. There were substantially more microhabitats related to standing dead and live habitat trees in unmanaged forest (e.g. woodpecker cavities, insect galleries and bore holes, branch holes, dead branches and fruiting bodies of fungi), whereas in managed forests there were more tree microhabitats related to management (e.g. exposed heartwood, coarse bark, and epiphytic plants). The results also indicate that disturbance, tree diameter, vitality, and species influence the density, diversity, and occurrence of tree microhabitats.
... Forest trees may bear many suitable cavities-either excavated by woodpeckers or as a result of wood decay (Kozák et al., 2018;Paillet et al., 2017;Remm & Lõhmus, 2011)which constitute the primary nesting sites of the wild colonies of A. mellifera (Crane, 1999;Kohl & Rutschmann, 2018;Oleksa et al., 2013). However, the current availability of tree cavities is limited by production-oriented forest management in Europe (Bütler, Lachat, Larrieu, & Paillet, 2013;Paillet et al., 2017). ...
... However, the current availability of tree cavities is limited by production-oriented forest management in Europe (Bütler, Lachat, Larrieu, & Paillet, 2013;Paillet et al., 2017). Across the main European forest types, unmanaged areas generally host far more tree cavities than their managed counterparts (Kozák et al., 2018;Paillet et al., 2017Paillet et al., , 2019. Records of wild honeybee colonies in tree cavities are mainly restricted to Northern Poland (Oleksa et al., 2013) and central Germany (Kohl & Rutschmann, 2018). ...
... This is likely related to the foraging and nesting habits of cavity excavators, which tend to prefer broadleaved trees (e.g., Kosinski et al., 2018;Rolstad, Rolstad, & Saeteren, 2000), as well as to the higher persistence of decayed cavities on broadleaved trees (Paillet et al., 2019;Wesołowski, 2011). Unsurprisingly, unmanaged forests displayed significantly higher cavity densities than their managed counterparts, due to the higher occurrence of large trees and snags in these forests (Kozák et al., 2018;Paillet et al., 2017). As a result, we predict that most European forests are cavity-poor except for some rare areas of unmanaged forest (Sabatini et al., 2018). ...
Article
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Recent studies reveal the use of tree cavities by wild honeybee colonies in European forests. This highlights the conservation potential of forests for a highly threatened component of the native entomofauna in Europe, but currently no estimate of potential wild honeybee population sizes exists. Here, we analyzed the tree cavity densities of 106 forest areas across Europe and inferred an expected population size of wild honeybees. Both forest and management types affected the density of tree cavities. Accordingly, we estimated that more than 80,000 wild honeybee colonies could be sustained in European forests. As expected, potential conservation hotspots were identified in unmanaged forests, and, surprisingly, also in other large forest areas across Europe. Our results contribute to the EU policy strategy to halt pollinator declines and reveal the potential of forest areas for the conservation of so far neglected wild honeybee populations in Europe.
... Examples of TreMs are woodpecker cavities, branch-or stembreakage, fungal fruiting bodies, injuries or epiphytes (Rita Bütler et al., 2020;Kraus et al., 2016;Larrieu et al., 2018). The ecological relevance of TreMs has been increasingly studied over the last years (Table 1) (Asbeck et al., 2019;Kõrkjas et al., 2021;Kozák et al., 2018;Larrieu et al., 2016;Paillet et al., 2019;Winter et al., 2014;Winter and Möller, 2008). In summary those studies prove that TreMs offer numerous ecological niches and contribute significantly to the structural richness in forest ecosystems (Winter et al., 2015). ...
... Tree diameter is the most frequently reported predictor of TreM abundance or richness followed by tree species (e.g. Asbeck et al., 2019;Basile et al., 2020;Großmann et al., 2018;Kozák et al., 2018;Laurent Larrieu et al., 2014;Paillet et al., 2019Paillet et al., , 2015aRegnery et al., 2013b;Vuidot et al., 2011;Winter et al., 2014;Winter and Brambach, 2011). Yet the range of tree species that have been analyzed for abundance or richness of TreMs is relatively small. ...
... Mixed-broadleaf-conifer forest stands were found to provide a greater number and more diverse TreMs compared to mixed or pure conifer forest stands (Asbeck et al., 2019). Further, TreM density and diversity increased with an increasing number of tree species in a forest stand (Kozák et al., 2018). Retained HTGs may provide more diverse TreMs in comparison to surrounding managed forests, since short-term cessation of forest management led to an increased TreM richness on a plot level (Winter and Möller, 2008). ...
Thesis
Habitat trees – one of the key elements of integrative retention approaches in European forests – are increasingly studied regarding their benefits to forest biodiversity. In this regard, treerelated microhabitats (TreMs) and deadwood serve as indicators of forest biodiversity. Specific recommendations of amounts of deadwood to be retained in managed forest stands to support related taxa are available, but not for TreMs. Retention of habitat trees aims to increase availability of TreMs in managed forests. To be able to refine selection criteria for habitat trees, I focused in this thesis on factors affecting TreMs on living trees. Therefore, I calculated species specific diameter thresholds bases on TreM occurrences, I investigated the effect of tree maintenance on TreMs in urban areas and I evaluated the short-term value of the retention of habitat tree groups. Chapter 1. The aim of this chapter was to explain TreM occurrence from a qualitative perspective by considering their diversity. Tree diameter at breast height (dbh), tree species, and canopy class were useful predictors of TreM diversity. TreM diversity on broad-leaved trees was on average higher than in conifers of the same diameter. In contrast to TreM abundance their diversity saturated towards higher dbh levels. Those TreM saturation levels were used to derive diameter thresholds. Habitat trees support not only more, but also more diverse, microhabitats in comparison to crop trees. Chapter 2. In this chapter I further developed the findings of chapter one and focused on the calculation of species specific diameter thresholds to precise recommendations for selecting habitat trees. Based on the relation between TreMs and tree diameter as well as TreMs and species I derived diameter thresholds for 18 European tree species (13 broad-leaved, 5 coniferous). Those thresholds refer to statistically disproportionate high levels of TreM richness or abundance. Complementing other aspects that need to be considered during habitat tree selection processes in managed forest stands, I recommend to select habitat trees with or close to a dbh of 70 cm for broadleaves and 86 cm for conifers. The differences of dbh thresholds between broadleaves and conifers as well as between species indicate species specific TreM dynamic. Chapter 3. In the third chapter, I investigated the TreM availability on urban trees along a maintenance gradient in Montréal, Canada. Intensive tree maintenance in urban trees led to levels of certain microhabitats such as cavities and injuries that were comparable to natural, unmanaged forests. Light maintenance of urban trees encouraged more crown deadwood than typical and intensive maintenance levels. My results underline the importance of conserving and maintaining large living trees, especially in urban areas to provide tree microhabitats. These results also demonstrate the important role of intensive tree maintenance in stimulating tree microhabitat development in urban areas. Chapter 4. Here, I addressed the effectiveness of habitat tree group (HTG) retention in forests of Baden-Württemberg, Germany, 10 years after the introduction of the approach. Large living trees (LLTs), standing deadwood and TreMs were significantly more abundant in HTGs than in reference plots. When retaining 5 % of a forest stand area as HTG, old-growth attributes increased significantly at the stand scale: amount of LLTs doubled and its volume almost tripled, and standing deadwood increased on average by 25 %. However, quantities of both attributes remain below recommended minimum thresholds. Retaining 5 % of stand area in HTG had a significantly positive effect on woodpecker cavities, rot holes and exposed heartwood, whereas 15 to 25 % area in HTGs would be required to increase stand level abundance of concavities, exposed sapwood or crown deadwood significantly. Retention of HTGs enriched managed, multiple-use forests with old growth structural attributes. Yet, the selection of HTGs could be made more efficient by focusing on forest patches with high tree volume or low tree density and by further considering snags, tree species mixture and LLTs as well as less vital trees. Overall the findings of this thesis suggest, that common tree attributes (species, diameter, vitality, canopy class, life status) can be used to predict the occurrence of TreMs. Species specific diameter thresholds can help to identify trees with higher levels of TreM richness. The specification of tree attributes in regard to TreMs allow to optimize habitat tree selection procedures. In addition or absence of trees rich in TreMs, tree maintenance could increase structural diversity. Intensively maintained trees providing comparable amounts of TreMs to trees from long-term unmanaged forests emphasize the relevance of artificially induced structures. To consider a holistic view on trees as biodiversity relevant feature throughout the landscape, I propose to expand further TreM research to urban and rural trees. Regardless how TreMs evolved and in which landscape they occur, the relation between TreMs and related taxa needs to be specified to strengthen the biodiversity indicating function of TreMs. Results from current TreM inventories, that followed standardized procedures, allow a approximation of TreM occurrence on a landscape level by linking species and diameter information to observed TreM abundances. To better understand development and persistence of TreMs repeated inventories were needed. Finally, my results allow to refine selection criteria of habitat trees based on the presence of TreMs and the consideration of species specific diameter thresholds. Furthermore, in absence of TreMs or when minimum diameters were not reached, I propose the possibility of artificial TreM creation to be useful for structural enrichment.
... Tree cavities are important ecological resources in forest ecosystems because they can provide refuges or breeding sites for animals (Sedgeley 2001;Aitken and Martin 2007;Goldingay 2009;Sverdrup-Thygeson et al. 2010;Remm and Lõhmus 2011;Kikuchi et al. 2013;Kozák et al. 2018;Zhang et al. 2019). It is estimated that tree cavities are used by over 300 vertebrate species in Australia and by over 1700 bird species globally (van der Hoek et al. 2017). ...
... Studies on tree cavities in different habitats have mainly been conducted in temperate forests (Kozák et al. 2018). Compared to temperate forests, tropical forests harbour more cavityusing species worldwide (Cockle et al. 2011b) and support a variety of cavity-nesting bird species (Monterrubio-Rico and Escalante-Pliego 2006). ...
Article
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Despite the influence of cavities on the survival and distribution of cavity-dependent fauna, the variation in the density and characteristics of tree cavities across different habitat types in tropical forests is unknown. In this study, we surveyed 26 312 living trees from 376 species and compared cavity density and characteristics (height, size, type, and orientation) across five habitat types (valley, low-slope, high-slope, high-gully, and high-plateau) in a 20-hectare tropical rainforest in southwest China. From a total of 2047 cavities, we found that cavity density was mainly driven by habitat rather than tree species richness or diameter at breast height (DBH), and the characteristics of cavities were not uniformly distributed across habitats. Cavities were significantly more abundant in high- and low-slope than high-plateau habitats. Compared with other habitats, more “butt hollow” cavity types were found in high-slope habitat and they occurred at a lower tree height, whereas more “crack” cavities were found in low-slope habitat and they had a narrower entrance diameter. Although the mean orientation of cavities faced towards the northeast, cavity orientation varied significantly across habitat types. Our results indicate that certain types of cavities are concentrated in specific habitat types, which can provide avenues for forest management and biodiversity conservation. We highlight the importance of habitat heterogeneity in providing resources for cavity nesters.
... In general, dead trees have more TreMs than living trees, and one study found 22 percent more TreMs on dead trees compared with live trees . The importance of tree size, tree species, and live or dead status to abundance and occurrence of TreMs appears to be consistent across several forest types: small-diameter stems have fewer TreMs than larger-diameter stems (Larrieu et al. 2012); broadleaved trees have more TreMs than conifers (Asbeck et al. 2019; and dead trees have more TreMs than live trees (Kozák et al. 2018). ...
... Mesic forest conditions in Hyrcanian forest align with annual precipitation, which is higher in western sites and at lower elevations (Gholizadeh et al. 2020); thus, we would expect to find a higher abundance of cavities in the western and lower elevations within the Hyrcanian forest. Cavity abundance is also highest in forests with a high density of large-diameter trees (Kozák et al. 2018). The unmanaged site had a higher proportion of large-diameter stems (15 percent of trees ≥75 centimeters dbh), which explains the findings of this study where there was a higher density of cavities in the unmanaged forest compared with the managed forest. ...
Article
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Tree-related microhabitats (TreMs) provide ecological niches in features for a variety of species in forests and are suitable indicators of biodiversity for certain taxa. The study objective was to compare the abundance and occurrence of TreMs in managed versus unmanaged Oriental beech (Fagus orientalis Lipsky) forests of northern Iran to quantify the effect of forest management on biodiversity indicators. We inventoried 3,954 trees to identify the number of trees with TreMs and quantify the occurrence of different types of TreMs. Managed forests averaged 25 trees with TreMs per hectare, and unmanaged forests averaged 41 trees with TreMs per hectare. In both forests, larger-diameter trees (≥50 centimeters diameter at breast height [dbh]) had more TreMs than smaller-diameter trees. TreMs were found on trees larger than a minimum size (32 centimeters dbh) and were more common on trees in poor health, as indicated by vitality class. According to our findings, managed forests have a lower diversity of TreMs than unmanaged forests. However, if management plans in deciduous forests include the retention of large-diameter trees during harvesting events, it is possible to balance providing TreMs within the forest while maintaining growth of economically valuable timber. Study Implications Forest biodiversity is time and labor intensive to quantify, and researchers have begun using tree-related microhabitats (TreMs) as a proxy for biodiversity. This study found TreMs occurred at lower abundances but had a similar occurrence of TreM groupings (cavities, injuries and wounds, deformation/growth form, and epiphytes) in managed Oriental beech (Fagus orientalis Lipsky) forests compared with unmanaged Oriental beech forests. Managed hardwood stands provided 25 TreMs per hectare, which is similar to numbers recommended for managing for biodiversity, and thus it may be possible to promote TreM creation and retention as an opportunity to increase forest biodiversity while also managing forests for timber production. Abundance of TreMs was associated with large-diameter trees and low-vitality trees (poor health). In deciduous forests managed for timber production, the retention of large-diameter trees is likely to align more closely with other management objectives than the retention of trees in poor health.
... According to Kraus et al. (2016) there are 64 types of TreMs; recently organized in a hierarchical typology by Larrieu et al. (2018) including "Form"; "Group" and "Type". Their occurrence and frequency are strictly linked to the forest naturalness and aging of trees (Kozák et al., 2018;Paillet et al., 2019;2017). They also represent useful proxies to assess the degree of naturalness of old-growth forests and forests with no recent harvesting activities (Santopuoli et al., 2019). ...
... We found that combined objective forestry originates higher TreMs occurrence compared to no management or passive management at least in the short time period (cf. Kozák et al., 2018). However, differences among management scenarios are not visibly pronounced, especially at early developmental stages (i.e. ...
Article
Mediterranean forests are important sources of income for society and represent biodiversity hotspots, characterized by a mosaic of forest structures, from short-rotation even-aged stands to old-growth forests. However, such increased complexity requires forest management to balance timber production with biodiversity conservation at various spatial scales. This study investigated the impacts of forest structures and management alternatives on the occurrence and richness of Tree-related Microhabitats (TreMs) – as proxies for forest biodiversity – in three Mediterranean forests in Italy. The generalized linear mixed model was applied to assess the relationship between a large set of forest structural parameters and the occurrence and richness of TreMs at the tree level, and resulted in an overall model accuracy higher than 80%. The same model was then implemented in hypothetical forest structures, resulting from no management, close-to-nature forestry and combined management system. Results show that at early developmental stages of the stand, no management slightly anticipates the occurrence of TreMs, while in mature forests, the combined forest management system effectively balances forest productivity with biodiversity conservation. The close-to-nature management system is recommended for promoting TreMs richness. Such findings might be used to support sustainable forest management and valorise the multifunctional role of Mediterranean forests.
... Microhabitats in forest ecosystems have gained considerable attention in recent times, as they are thought to support or significantly facilitate biodiversity in forest ecosystems (Kozák et al., 2018;Larrieu et al., 2018;Regnery et al., 2013). Of all the microhabitats in forests, cavities are among the easiest to observe and monitor while simultaneously being rather long-lasting features. ...
... directly to other forest features. It remains, however, an important task to document how cavities are related to forest biodiversity more generally (Gao et al., 2015), although this connection is already quite widely supported (Kozák et al., 2018;. ...
Article
Tree cavities are microhabitats used by multiple taxa and are considered indicators of forest biodiversity. The factors that affect cavity occurrence and its dynamics are poorly known. We studied tree-and stand-level factors that affect cavity persistence in boreal forests. Cavities of Eurasian Three-toed Woodpeckers (Picoides tridactylus) (n = 654) were surveyed in a 170 km 2 area in southern Finland for 31 years during 1987-2017. In total, 447 cavities were lost during the study period: 329 to tree fall or breakage, 72 to cavity damage, and 46 to logging. With the Kaplan-Meier method and Cox proportional hazards models, we analysed which tree-and stand-level factors affected the risk of a cavity to be damaged or lost due to tree fall. The median lifespan of cavities was 10 years, and both tree-and stand-level factors affected the persistence of cavities. Cavities in managed forest areas with low territory occupancy rates were more at risk of tree fall and cavity damage than in other types of forest areas. In all nest tree species, with the exception of European aspen (Populus tremula), the risk of cavity loss to tree fall declined with increasing tree diameter. Moreover, the risk of cavity loss to tree fall was higher in dead trees than in healthy and weakened trees. Cavities in deciduous tree species other than aspen were more at risk of damage than in other tree species. Furthermore, the risk of cavity damage was greater in cavities located lower in a tree. This study showed that factors like the tree species, and size and condition of a tree modify the persistence of woodpecker-made cavities. Consequently, it is likely that these factors influence the value of cavities as microhabitats and how these cavities can be used as indicators of forest biodiversity. Understanding the dynamics of cavities in forest habitats appears critical for the use of cavities as general biodiversity indicators .
... However, close-range remote sensing techniques are able to describe small-scale structural complexity of forests in increasing detail [4,[39][40][41][42]. TreM inventories and RS techniques are often used to answer similar research questions, for instance the quantification of old-growth attributes in forests [39,43] and the selection of habitat trees [32,44]. If remotely-sensed data can predict the range of forest structures that offer a high abundance and richness of TreMs, this would constitute a major step towards a more efficient and objective selection of habitat trees as retention elements for biodiversity conservation. ...
... Despite the inclusion of some strict reserves and other protected areas in the study, most plots are located in forests that are managed or where the structure is still strongly influenced by previous management. It is possible that old-growth forests will show a stronger link between the present RS indices and TreM assessments for structural elements affecting forest biodiversity [39,43]. ...
Article
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The retention of structural elements such as habitat trees in forests managed for timber production is essential for fulfilling the objectives of biodiversity conservation. This paper seeks to predict tree-related microhabitats (TreMs) by close-range remote sensing parameters. TreMs, such as cavities or crown deadwood, are an established tool to quantify the suitability of habitat trees for biodiversity conservation. The aim to predict TreMs based on remote sensing (RS) parameters is supposed to assist a more objective and efficient selection of retention elements. The RS parameters were collected by the use of terrestrial laser scanning as well as unmanned aerial vehicles structure from motion point cloud generation to provide a 3D distribution of plant tissue. Data was recorded on 135 1-ha plots in Germany. Statistical models were used to test the influence of 28 RS predictors, which described TreM richness (R 2 : 0.31) and abundance (R 2 : 0.31) in moderate precision and described a deviance of 44% for the abundance and 38% for richness of TreMs. Our results indicate that multiple RS techniques can achieve moderate predictions of TreM occurrence. This method allows a more efficient and objective selection of retention elements such as habitat trees that are keystone features for biodiversity conservation, even if it cannot be considered a full replacement of TreM inventories due to the moderate statistical relationship at this stage.
... Woodpeckers, for instance, are the main source of cavities for secondary cavity-nesters (sensu Newton 1994) in intensively managed boreal and temperate forests (Pakkala et al. 2018), while in primeval temperate forests secondary cavity nesters rely mostly on natural cavities created by decay processes (Wesołowski 2007). In primeval forests, natural disturbance leads the forest succession and unhampered tree ageing processes and TreM development is not suppressed by management (Kozák et al. 2018). Therefore, sustainable and multi-purpose forest management can learn from primeval forest dynamics that tree size does not need to be the ultimate feature for tree selection, as it is not the ultimate tree feature involved in woodpecker tree selection. ...
Article
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What kind of tree should be preserved from logging for biodiversity conservation is a matter of debate. Large and old trees are potential candidates due to the structures they can bear, like cavities and other tree-related microhabitats (TreMs). One of the most studied TreM is woodpecker-made cavities, which, in addition to be breeding sites for primary cavity-nesters, are often the main breeding sites for secondary cavity-nesters, especially in managed forests. Therefore, understanding which trees woodpeckers select for cavities is relevant to forest management, especially in management regimes where indi-vidual trees are logged or spared, as in retention forestry. We used data from a forest inventory, TreM inventory and wood-pecker counts in one-hectare plots in the Black Forest (southwest Germany) to investigate which features make a retention tree suitable for woodpeckers. By employing a resource selection probability function, we tested several variables for their influence on the probability of tree choice by woodpeckers including altitude, tree species, TreM richness and abundance, diameter at breast height (DBH) and deviation from the mean DBH per plot. The results show that the probability of selection by woodpeckers does not correlate with individual tree diameter. Instead, the probability is driven mainly by the deviation from the mean DBH per plot. We were able to identify a relative size for the selection of trees indicating that woodpeckers prefer trees that are about 15–20 cm larger than the mean DBH per plot. Thereby, we argue, that using abso-lute diameter thresholds to select retention might not be the best management solution in the short-term, as in managed forests woodpeckers might select sub-optimal trees. Apparently, more knowledge concerning relative thresholds, as detected in our study, is required to improve our understanding of the potential ecological value of retention trees.
... There is an increasing number of studies recognizing the importance of habitat structures for biodiversity, especially in recent years (e.g. Augustynczik et al., 2019;Kozák et al., 2018;Nagel et al., 2017). Habitat structures include standing and lying deadwood at different stages of decay (Floren et al., 2014;Lassauce et al., 2011;Parisi et al., 2016), as well as old and veteran trees providing microhabitats or big branches, holes, cavities and water bodies (e.g. ...
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The accelerating global rate of species extinctions and the inevitable human impacts on biodiversity have increased the need to conserve, restore and use ecosystems sustainably. Indicators for biodiversity are the most frequently used tool to monitor the status of biodiversity, changes to biodiversity, and the effects of management actions. In this study, we aim to assess the magnitude of studies on indicators for biodiversity (IB) in European forest ecosystems, establish and analyze the link between IB and silvicultural management measures (MM), and define indicators for management (IM), that aim to support biodiversity at the stand and landscape level. We performed a systematic literature review and analyzed data from 162 studies. We identified 9 IB groups, cor-responding to 32 IB and linked them to 7 IM groups corresponding to 44 IM. Arthropods, birds, and plants are the most frequently used IB in European managed forests. We found IB with clear links to specific IM, such as saproxylic species and Collembola (collembolans) with deadwood, bird families (Passeriformes, Piciformes, Accipitriformes) with links to microhabitats, and ground-dwelling species with links to regeneration. We iden-tified 17 species as proposed umbrella species based on the studies examined. This review shows that high structural diversity is associated with an increase in diversity, especially with regard to vascular plants, birds and ground-dwelling species. The adaptation of forest management for biodiversity requires regular active moni-toring of IM to assess the temporal and spatial changes and of IB to assess the effectiveness of measures.
... The finding that large trees supported a higher abundance and richness of TreMs in most of our models (9 out of 13) has been reported in similar studies in managed forests (Larrieu and Cabanettes 2012; Paillet et al. 2017). Recently, it has been shown that this trend also holds true in primary beech forests (Kozák et al. 2018). ...
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Habitat trees, which provide roosting, foraging and nesting for multiple taxa, are retained in managed forests to support biodiversity conservation. To what extent their spatial distribution influences provisioning of habitats has rarely been addressed. In this study, we investigated whether abundance and richness of tree-related microhabitats (TreMs) differ between habitat trees in clumped and dispersed distributions and whether the abundance of fifteen groups of TreMs is related to tree distribution patterns. To identify habitat trees, we quantified TreMs in temperate mountain forests of Germany. We determined clumping (the Clark-Evans index), size of the convex hull, diameter at breast height, as well as altitude, slope and aspect of sites for their possible influence on TreMs. We additionally determined the difference in TreM abundance and richness among four options of selecting five habitat trees per ha from 15 candidates: (a) the most clumped trees, (b) five randomly selected and dispersed trees, (c) the single tree with highest abundance or richness of TreMs and its four closest neighbors and (d) a "reference selection" of five trees with known highest abundance or richness of TreMs irrespective of their distribution. The degree of clumping and the size of the convex hull influenced neither the abundance nor richness of TreMs. The reference selection, option (d), contained more than twice the number of TreMs compared to the most clumped, (a), or random distributions, (b), of five habitat trees, while option (c) assumed an intermediate position. If the goal of habitat tree retention is to maximize stand-level abundance and richness of TreMs, then it is clearly more important to select habitat trees irrespective of their spatial pattern.
... Dead trees are of great ecological value for a variety of taxonomic groups (Stokland et al., 2012;Kozák et al., 2018;Runnel et al., 2019). Many species of fungi, plants, and animals are more or less closely associated with deadwood (DW), which offers suitable microhabitats for growth and reproduction, providing shelter and a source of nutrients (e. g., Unar et al., 2017;Lešo et al., 2019;Grinde et al., 2020). ...
Article
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Deadwood (DW) is a crucial component of habitats, with both its volume and diversity considered critical for saproxylic organisms. Deadwood position, thickness, snag height, species composition, and decay stage were studied in the context of eight factors characterizing habitats, stands, and management types. A multivariate multiple regression model was used to analyze data from 29,098 sample plots. Deadwood diversity (a 5-dimensional dependent variable) was found to strongly depend on DW volume in a given area and on the species composition of the stand. A less pronounced effect was exerted by site fertility and moisture, the age and DBH structure of the stand, and terrain type. The model also revealed that the location of the stand in managed or unmanaged areas did not have a direct impact on deadwood diversity, with stand features being more important. Analysis of individual qualitative characteristics showed that DW thickness was affected by the same seven factors as DW diversity. DW position and decay stage were influenced by four factors: site fertility and moisture as well as stand age and species composition. In addition to the species composition of stands, DW species composition was positively influenced by more fertile and moist sites and a more varied DBH structure of stands. A significant negative effect was identified for high DW volume, which indicates that the deadwood accumulated in a stand tends to be derived from the tree species that was most vulnerable to mortality at a given time. Snag height variation was influenced by such stand characteristics as age, DBH structure, and species composition; the other significant factors were DW volume and terrain type. The diversity levels of individual DW characteristics were significantly and positively correlated, which means that all of them often revealed high or low diversity at the same time. Our study showed that forests with low DW volume additionally face the problem of DW quality. Thus, efforts to increase DW volume should be focused on those DW characteristics that are lacking (large trees, species diversity, and height variation of snags). DW diversity is lower in younger stands, with little DBH variation, and in forests which are more easily accessible, located mostly in the lowlands, and growing on less fertile and dry or mesic sites.
... Certains types de DMH s'observent plu- tôt sur les feuillus, par exemple les den- drotelmes (cavités remplies d'eau) et les fentes, d'autres davantage sur les résineux (par exemple les balais de sorcières). Les peuplements mixtes présentent donc une plus grande diversité de DMH que les peu- plements monospécifiques, surtout lors- qu'ils contiennent également des essences pionnières et secondaires telles que le bouleau et le peuplier tremble (Larrieuet al. 2012).L'exploitation forestière influe sur la diversité ainsi que sur la densité et la distribution spatiale des arbres-habi- tatsLa densité de DMH est naturellement très forte dans les forêts: selon des études me- nées dans les Carpates roumaines et ukrai- niennes, ainsi que dans les Alpes dina- riques(commarmot et al. 2013 ;KozáK et al. 2018), un arbre sur trois, voire sur deux, porte des DMH. Dans ces forêts mixtes, dominées par les feuillus, on a dé- nombré en moyenne plus de 400 DMH/ ha. ...
Article
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La biodiversité joue un rôle important dans le fonctionnement des écosystèmes forestiers. Les arbres-habitats sont des éléments clés pour les espèces vivant en forêt. Des spécialistes européens ont élaboré une typologie détaillée des dendromicrohabitats, petits milieux de vie portés par les arbres et qui sont indispensables à des milliers d’organismes spécialisés. La présentation homogène des formes, groupes et types de dendromicrohabitats ainsi définis facilite la mise en oeuvre des recommandations dans la pratique forestière. En outre, les données homogénéisées qui résultent de l’emploi de cette typologie sont utiles pour le monitoring de la biodiversité forestière ou pour l’évaluation des résultats de mesures destinées à promouvoir cette diversité.
... Literature suggests the large trees act as keystone habitat features (DeMars, Rosenberg, & Fontaine, 2010). The rough, corrugated bark, and multiple microhabitats, like small places of rot, of larger trees host insects, providing rich and abundant forage for birds of multiple guilds (Großmann, Schultze, Bauhus, & Pyttel, 2018;Kozák et al., 2018;Larrieu & Cabanettes, 2012). Studies have tied specifically bark-foraging bird species to large-diameter trees (Pennington & Blair, 2011;Whelan & Maina, 2005). ...
Article
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Many studies have demonstrated the importance of early‐successional forest habitat for breeding bird abundance, composition, and diversity. However, very few studies directly link measures of bird diversity, composition and abundance to measures of forest composition, and structure and their dynamic change over early succession. This study examines the relationships between breeding bird community composition and forest structure in regenerating broadleaf forests of southern New England, USA, separating the influences of ecological succession from retained stand structure. We conducted bird point counts and vegetation surveys across a chronosequence of forest stands that originated between 2 and 24 years previously in shelterwood timber harvests, a silvicultural method of regenerating oak‐mixed broadleaf forests. We distinguish between vegetation variables that relate to condition of forest regeneration and those that reflect legacy stand structure. Using principal components analyses, we confirmed the distinction between regeneration and legacy vegetation variables. We ran regression analysis to test for relationships between bird community variables, including nesting and foraging functional guild abundances, and vegetation variables. We confirmed these relationships with hierarchical partitioning. Our results demonstrate that regenerating and legacy vegetation correlate with bird community variables across stand phases and that the strength with which they drive bird community composition changes with forest succession. While measures of regeneration condition explain bird abundance and diversity variables during late initiation, legacy stand structure explains them during stem exclusion. Canopy cover, ground‐story diversity, and canopy structure diversity are the most powerful and consistent explanatory variables. Our results suggest that leaving varied legacy stand structure to promote habitat heterogeneity in shelterwood harvests contributes to greater bird community diversity. Interestingly, this is particularly important during the structurally depauperate phase of stem exclusion of young regenerating forests. Our results demonstrate that regenerating and legacy vegetation correlate with bird community variables across stand phases and that the strength with which they drive bird community composition changes with forest succession. While regeneration explains bird variables during late initiation, legacy stand structure explains them during stem exclusion. Canopy cover, ground‐story diversity, and canopy structure diversity are the most powerful and consistent explanatory variables. Results suggest that leaving varied legacy stand structure to promote habitat heterogeneity in shelterwood timber harvests contributes to greater bird community diversity, particularly during the depauperate phase of stem exclusion.
... For example, the TreM form "Tree injuries and exposed wood" can be abundant in managed forests due to injuries caused by logging activities. Other factors influencing TreMs have been tested, such as local climatic and topographic conditions Asbeck et al., 2021b), spatial patterns (Kozák et al., 2018;Asbeck et al., 2019Asbeck et al., , 2020bMartin et al., 2021b) or the influence of tree age (Kõrkjas et al., 2021b), but with less marked results. ...
Article
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Sustainable management of forest ecosystems requires the use of reliable and easy to implement biodiversity and naturalness indicators. Tree-related microhabitats (TreMs) can fulfill these roles as they harbor specialized species that directly or indirectly depend on them, and are generally more abundant and diverse in natural forests or forests unmanaged for several decades. The TreM concept is however still recent, implying the existence of many knowledge gaps that can challenge its robustness and applicability. To evaluate the current state of knowledge on TreMs, we conducted a systematic review followed by a bibliometric analysis of the literature identified. A total of 101 articles constituted the final corpus. Most of the articles (60.3%) were published in 2017 or after. TreM research presented a marked lack of geographical representativity, as the vast majority (68.3%) of the articles studied French, German or Italian forests. The main themes addressed by the literature were the value of TreMs as biodiversity indicators, the impact of forest management on TreMs and the factors at the tree- and stand-scales favoring TreMs occurrence. Old-growth and unmanaged forests played a key role as a “natural” forest reference for these previous themes, as TreMs were often much more abundant and diverse compared to managed forests. Arthropods were the main phylum studied for the theme of TreMs as biodiversity indicators. Other more diverse themes were identified, such as restoration, remote sensing, climate change and economy and there was a lack of research related to the social sciences. Overall, current research on TreMs has focused on assessing its robustness as an indicator of biodiversity and naturalness at the stand scale. The important geographical gap identified underscores the importance of expanding the use of the TreMs in other forest ecosystems of the world. The notable efforts made in recent years to standardize TreM studies are an important step in this direction. The novelty of the TreM concept can partially explain the thematic knowledge gaps. Our results nevertheless stress the high potential of TreMs for multidisciplinary research, and we discuss the benefits of expanding the use of TreMs on a larger spatial scale.
... Despite the inclusion of some strict reserves and other protected areas in the study, most plots occurred in forests that are managed or where the structure is still strongly influenced by previous management. It is possible that old-growth forests will show a stronger link between RS indices and TreM assessments for structural elements affecting forest biodiversity (Kozák et al., 2018;. ...
Thesis
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Forest management alters the spatial structure of forests, which directly shapes the biodiversity, processes and functioning of such ecosystems. While forest structure is commonly quantified using field-based forest management metrics, close range (distances < 150m) remote sensing techniques are able to describe the distribution of material in 3D space with very high detail and precision. Since manual inventories of forest structure are labor intensive and suffer from observer biases remote sensing techniques offer new possibilities for efficient and objective quantifications of forest structure. To investigate the impacts of forest management on stand structure, new indices and metrics based on 3D point clouds have been developed and validated. This dissertation is structured in three publications (Chapters 4 - 6), starting with a methods paper on UAV flight planning optimization, followed by a comparison of tree related microhabitat inventories and close range remote sensing indices for stand structure quantification, and ending with a validation of a remote sensing index based on a forest expert survey. For the first paper, a technical flight planning optimization was conducted for unmanned aerial vehicles structure from motion as a basis for optimal data acquisition (Chapter 4). The image forward overlap and ground sampling distance were varied, and the parameters of the resulting geometric model completeness in 2D and 3D space that differed could be independently quantified. While finer resolutions led to a better representation of smaller forest details and a better representation of the understory, the model completeness suffered from it. A higher forward image overlap can compensate for this if the overlap is very high (>95%). Tree related microhabitat (TreM) inventories are unlike remote sensing based indices but have a similar aim of quantifying forest structures, which can be accumulated to a stand level. TreMs themselves are special tree level structures such as forks, cavities and fungi. While both approaches have different perspectives on forest structure, their common goal of forest stand structure quantification make the respective insights from these methods worth comparing (Chapter 5). A significant correlation with a weak R² (0.30) indicate that these two measures are linked but that their representation of stand structure is complementary. Foresters and other forest experts are of major relevance to the topic of implementation of retention management and the selection of retention patches, since they are the decision makers and practitioners in this sector. The judgement of those experts could be biased by additional objectives and individual preferences. In an extensive online survey (n=444), experts were asked to quantify stand structure on 360 degree panoramic images in an interactive viewer. The expert responses were compared to stand structural complexity metrics derived from terrestrial laser scans, which were taken at the same location from the same viewpoint. The standard deviation of the expert judgements were high, which indicates the necessity of objective measurements. The laser scanning based index significantly correlated with the expert judgements, which shows that neither the expert ratings nor the scanning index are random and that laser scanning is an option for more objective decision making processes. However, experts in the field might take a variety of additionally relevant criteria (e.g. rareness of the habitat in landscape, special tree features, breeding places) into account, which should not been overlooked. In summary, this dissertation validated and adapted several indices based on close range remote sensing techniques and showed their potential as monitoring tools and assistance for the forest management decision-making processes.
... This truncated the relationships for the investigated set of microhabitats and made them imprecise for the larger diameter categories. Further research on the last remnant of old-growth primeval forests in Europe [51,52] is therefore needed to bridge this gap and better understand microhabitat dynamics over the whole lifespan of the tree. ...
Article
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 highest Gini indices were found within mixed uneven-aged plots, and pure even- aged plots, which were relatively homoge- nous, had the lowest Gini indices. Large tree size diversity may ensure a wide range of habitats and provide higher levels of bio- diversity in forest ecosystems (Pach & Podlaski 2015, Kozák et al. 2018). ...
Article
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Restoring the structural characteristics of secondary old-growth forests that were previously managed is increasingly debated to help increase the area of more complex forests which provide a broader array of forest services and functions. The paucity of long-term data sets in Central Europe has limited our ability to understand the ongoing ecological processes required for effective restoration programs for old-growth forests. To address this, we used repeated census data from eight permanent plots to evaluate forest structural dynamics over a 12-year period in the largest complex of European beech (Fagus sylvat-ica L.) forests in the Czech Highlands without intensive forestry intervention for almost 50 years. Our results showed that previously managed forests can exhibit structural qualities typically associated with old-growth forests after management has ceased for a period. The stand structural characteristics (e.g., density of large and old trees) is comparable with protected reserves of old-growth European beech-dominated forests. The average stand age was 196 years, but the oldest tree was 289 years old. The annual mortality rate was 0.43% for all species, and the U-shaped distribution indicating size-dependent mortality is likely an important process that is balanced by the turnover of new tree recruitment. During the study period, we detected that the diameter distribution tended towards a rotated sigmoid distribution. The lasting effects of the most recent forest management are evident in the scarcity of dead wood, and a prolonged process of dead wood accumulation has begun. Thus, the abandonment of all management activities in near-natural forest reserves, including dead wood removal, will ensure that the forests will develop characteristics typical of old-growth forests.
... Within each 10-ha polygon, two sample plots were set. In this way, a total of 48 plots were randomly superimposed in the study area (for details, see [33]). Each established plot was divided into three circularly fixed nested plots: An inner plot (radius 7.98 m, area 200 m 2 ), a middle plot (radius 17.84 m, area 1000 m 2 ), and an outer plot covering whole plot area (radius 21.85 m, area 1500 m 2 ). ...
Article
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Structural indices are often proposed as guiding measures for increasing structural heterogeneity. However, few studies have examined the association between such indices and conventional stand attributes. The primary objectives of this study were to evaluate changes in structural heterogeneity and tree species diversity at different plot sizes and to quantify the relationships between conventional stand attributes (mean tree diameter, absolute tree density, basal area, species proportion) and structural indices in a mixed old-growth forest in Southeast Europe. Paired tests were used to identify significant changes in structural heterogeneity with increased plot area, while the relationships between stand attributes and analyzed indices (Gini, diameter differentiation, species mingling, and Shannon's index) were evaluated with Pearson's correlations. The index values of Gini, diameter differentiation, and tree species mingling were rather stable with the increase of plot size, whereas tree species diversity increased significantly with the increase of plot area from 200 m2 to 1500 m2. The measures of tree species mingling and tree species diversity were strongly associated with each other, while their association with diameter variability was weak to moderately strong. Tree species mingling index was strongly associated with the changes in tree species proportions. However, conventional stand attributes were generally not strongly correlated with the examined indices. For restoring and maintaining old-growth characteristics, forest managers may use structural indices to increase small-scale structural heterogeneity, tree species mingling, and diversity, but only as an additional set of measures, not as surrogates for conventional stand attributes.
... Instead, they are one of the main drivers shaping stand structure via biological legacies that are left from the pre-disturbance ecosystem [10,[16][17][18]. As a result, unique structures are formed which perform as habitats for many endangered, forest-specialist species [19,20]. ...
Article
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Research Highlights: Past disturbances occurred naturally in primary forests in the Southern Carpathians. High-and moderate-severity disturbances shaped the present structure of these ecosystems, which regenerated successfully without forestry interventions. Background and Objectives: Windstorms and bark beetle outbreaks have recently affected large forest areas across the globe, causing concerns that these disturbances lie outside the range of natural variability of forest ecosystems. This often led to salvage logging inside protected areas, one of the main reasons for primary forest loss in Eastern Europe. Although more than two-thirds of temperate primary forests in Europe are located in the Carpathian region of Eastern Europe, knowledge about how natural disturbances shape the forest dynamics in this region is highly essential for future management decisions. Material and Methods: We established our study in a primary forest valley situated in the centre of the largest temperate primary forest landscape in Europe (Făgăras , Mountains). A dendrochronological investigation was carried out to reconstruct the natural disturbance history and relate it to the present forest structure. Results: The dendrochronological analysis revealed high temporal variability in the disturbance patterns both at the patch and stand level. Moderate severity disturbance events were most common (20-40% of canopy disturbed in 60% of the plots) but high severity events did also occur (33% of the plots). Regeneration was spruce-dominated and 71% of the seedlings were found on deadwood microsites. Conclusions: We conclude that the current structure of the studied area is a consequence of the past moderate-severity disturbances and sporadic high-severity events. The peak in disturbances (1880-1910) followed by reduced disturbance rates may contribute to a recent and future increase in disturbances in the Făgăras , Mts. Our findings show that these disturbance types are within the range of natural variability of mountain spruce forests in the Southern Carpathians and should not be a reason for salvage logging in primary forests from this area.
... If available, trees harbouring microhabitats shall be favoured for retention when making a decision on retaining a group of trees or individual trees (Bouget et al., 2014a(Bouget et al., , 2014bMüller et al., 2014; Fig. 1, Table 3). Trees with microhabitats often bear some amount of deadwood providing necessary habitats for a range of species (or groups of species) to grow, nest or forage as a part of their life cycle (Winter and Möller, 2008;Vuidot et al., 2011;Larrieu et al., 2014;Paillet et al., 2017;Larrieu et al., 2018;Kozák et al., 2018). The retention focus shall be also made on individuals with the potential to develop fully functioning microhabitats over time (e.g. ...
... Es existiert bisher nur eine begrenzte Anzahl an Forschungsarbeiten.Waldbestände, die sich aus verschiedenen Baumarten zusammensetzen, sind weniger anfällig gegenüber abiotischen und biotischen Störungen. Darüber hinaus wirkt sich eine hohe Baumartenvielfalt auf regionaler Ebene positiv auf das Vorkommen und die Vielfalt an Baum-Mikrohabitaten aus12,13 .Die Baumartenvielfalt beeinflusst die Entwicklung verschiedener Gemeinschaften von Makropilzen. Die Anzahl holzzersetzender Makropilze steigt mit der Anzahl an vorkommenden Baumarten auf Bestandesebene14 . ...
Technical Report
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The accelerating rate of species extinction worldwide and the inevitable impact of human activity on biodiversity have increased the demand for conservation, habitat restoration and the sustainable use of ecosystems. Biodiversity indicators are the most commonly used tool to monitor the status and changes of biodiversity and the related impact of management measures. Based on an extensive literature review of studies linking forest management to biodiversity, we identified indicators for biodiversity in forest ecosystems and established their link to forest management measures. In addition, we defined management indicators to support biodiversity at stand and landscape level. The research resulted in 162 studies creating the base for the identification of nine groups of biodiversity indicators, which were linked to seven management indicators. To support biodiversity, we summarized 14 forest management measures. The most common biodiversity indicators reported in European managed forests so far are arthropods, birds and vascular plants. For some of these species, we identified clear relationships with certain forest management indicators, such as deadwood-inhabiting insects and springtails with deadwood, bird families (passerines, woodpeckers) with habitat structures and ground-dwelling insects with a heterogeneous stand structure. The targeted promotion of deadwood or habitat structures and the promotion of a diverse structure in the forest stand are therefore measures that severely promote biodiversity. In general, a high structural diversity is associated with an increase in diversity, especially regarding vascular plant species, bird species and soil-dwelling species. The adaptation of forest management to promote biodiversity requires a regular monitoring to assess the effectiveness of the measures applied. The present catalogue not only recommends management measures to promote biodiversity, but also offers suggestions for biodiversity as well as forest monitoring to assess the effectiveness of the measures. The forest monitoring refers to parameters of forest structure and management and the biodiversity monitoring refers to species groups and structural elements of biodiversity at landscape level. In addition, it is highlighted whether the individual measures contribute to the adaptation of forests to climate change or increase their adaptive capacity to climate change.
... The long temporal continuity, coupled with natural dynamics of regeneration and disturbance processes, contributes at creating a high structural complexity in these forests (Franklin and Pelt 2004). This complexity translates into a high variety and number of forest microhabitats (Kozák et al. 2018). These include deadwood, tree cavities, fruiting bodies of saproxylic fungi and other epiphytic and epixylic structures, and provide habitat or shelter to a range of beetles, birds, bats and other taxa. ...
... They have highlighted the key roles of tree species, tree diameter at breast height (dbh) and status (i.e. 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). ...
Article
Tree-related microhabitats (TreMs) have been identified as key features for forest-dwelling taxa and are often employed as measures for biodiversity conservation in integrative forest management. However, managing forests to ensure an uninterrupted resource supply for TreM-dwelling taxa is challenging since TreMs are structures with a limited availability, some of which are triggered by stochastic events or require a long time to develop. At the tree scale, the role of tree species, diameter at breast height (dbh) and status (i.e. living vs standing dead) for favouring TreM occurrence has been quantified and modelled in several studies, since these tree features are routinely recorded in the field. However, TreM occurrence remains difficult to predict, hampering the elaboration of applicable management strategies that consider TreMs. Using an international database encompassing 110,000 trees, we quantified the explanatory power of tree species, dbh, status, time since last harvest and plot context for predicting TreM occurrence at the tree level. Plot context is so far a “black box” that combines local environmental conditions, past and current management legacies, with local biotic features that have high explanatory power for predicting TreM occurrence. Then, based on the literature, we established a set of 21 factors related to site, stand and tree features for which there is a strong assumption that they play a key role in TreM formation. Finally, we identified a sub-set of nine features that should be recorded in the future to provide additional information to enable better prediction of the occurrence of particular TreMs: (i) at plot level: slope, exposure, altitude and presence of cliffs; and (ii) at tree level: bark features, phyllotaxis and compartmentalization capacity of the tree species, plus ontogenic stage and physiological state of the individual tree sampled.
... These structures are commonly named tree-related microhabitats (hereafter TreMs). Several studies have described TreMs profile in old-growth forests (Kozák et al. 2018, Paillet et al. 2017, as well as the dynamics of TreMs in unmanaged temperate mountain mixed forests ). In the original definition of Larrieu et al. (2018), TreMs are "distinct, well-delineated structures occurring on living or standing dead trees that constitute a particular and essential substrate or life site for species or communities during at least a part of their life cycle to develop, feed, shelter or breed". ...
Article
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Tree-related microhabitats (hereafter TreMs) are structures occurring on trees, such as rot holes, cavities, large nests, mould, fruiting bodies and myce-lia of decomposer fungi. TreMs have been widely recognized as important sub-strates and structures useful for biodiversity conservation in forest ecosystems , and they can be used as indicators for describing and monitoring forest naturalness. However, most studies on the occurrence of TreMs have been mainly done in forest ecosystems of Central Europe, while less research has been conducted in Mediterranean mountain forests. In this study, we investigated the diversity and abundance of 23 types of TreMs on living trees and on deadwood in seven Mediterranean mountains unmanaged forests located in the Apennines (Italy). The abundance of TreMs was evaluated by counting the number of TreMs per tree, while the diversity of TreMs was evaluated by means of the Shannon-Wiener index. We focused on the relationships between diversity and abundance of TreMs, and tree size (e.g., diameter, height, volume), and the time since the last harvest. Among the investigated stands, 2612 living trees, 457 standing dead trees and snags, and 1247 lying dead-wood pieces were analysed. For living trees, a generalized linear mixed model was applied to test the effect of several variables on the abundance of TreMs per tree. Diameter at breast height (DBH) of tree stems influenced the abundance and diversity of TreMs. The time since the last harvest also significantly affected the probability that TreMs could be formed in a long-term perspective. The interaction of the predictors "DBH 2 " and "Years since the last har-vest" generated a better model than the one in which the two variables were kept separate. Indeed, these two factors together would better represent the transition of a previously managed forest to a more natural state over time. This study might provide useful information to land managers committed to forestry practices towards sustainable management and biodiversity conservation , especially referring to survey and inventory of forests of high nature value.
... Third, larger trees may offer more roosting sites for tree-dwelling bat species compared to smaller ones (Tillon et al., 2016). Diameter at breast height is one of the main driver of TreM diversity (Larrieu et al., 2014;Kozák et al., 2018;Asbeck et al., 2019) and TreM formation accelerates as trees grows (Courbaud et al., 2017). This is also confirmed for isolated trees by the positive and Fig. 2. Predicted bat responses to tree size with the 95% confidence interval (obtained from our best models): (a) predicted P. pipistrellus activity (i.e. ...
Article
Isolated trees are increasingly recognised as playing a vital role in supporting biodiversity in agricultural landscapes, yet their occurrence has declined substantially in recent decades. Most bats in Europe are tree-dependent species that rely on woody elements in order to persist in farmlands. However, isolated trees are rarely considered in conservation programs and landscape planning. Further investigations are therefore urgently required to identify which trees – based on both their intrinsic characteristics and their location in the landscape – are particularly important for bats. We acoustically surveyed 57 isolated trees for bats to determine the relative and interactive effects of size, tree-related microhabitat (TreM) diversity and surrounding landscape context on bat activity. Tall trees with large diameter at breast height and crown area positively influenced the activity of Pipistrellus pipistrellus and small Myotis bats (Myotis spp.) while smaller and thinner trees favoured M. myotis activity. The diversity of TreMs that can be used as roosts had a positive effect on (i) Barbastella barbastellus activity only when trees were relatively close (<50 m) to woody patches, (ii) Pipistrellus nathusii/kuhlii activity only in the most heterogeneous landscapes, and (iii) Myotis spp. activity only in the most forested environment (>10% within 100 radius scale). The potential benefits of isolated trees for bats result from ecological mechanisms operating at both tree and landscape scales, underlining the crucial need for implementing a multi-scale approach in conservation programs. Maintaining the largest and most TreM-diversified trees located in the most heterogeneous agricultural landscapes will provide the greatest benefits.
... As TreM are generally more abundant on hardwood species compared to coniferous species, as well as on large trees compared to the smaller ones (Paillet et al. 2019), trees in boreal forests may be less susceptive to develop TreM. Thus, the density of TreM trees (from 34.3 to 133.3 TreM trees/ha in the different clusters) observed in our study was unsurprisingly lower than that observed by Kozák et al. (2018) in primary forests dominated by European beech (Fagus sylvatica L.) in Europe (277.8 trees/ha). ...
Article
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Tree-related microhabitats (TreM) and deadwood are two forest attributes providing essential resources for biodiversity conservation and ecosystem services. Old-growth forests are generally defined by a high abundance and diversity of TreM and deadwood, but little is known about TreM and deadwood dynamics once the old-growth stage is reached, in particular in the boreal biome. In this context, knowledge on TreM and deadwood dynamics in old-growth forest stands is necessary to better understand how these forests contribute to biodiversity and ecosystem services. The aim of this study is thus to determine how TreM, and deadwood abundance and diversity vary within boreal old-growth forests. To reach this objective, we surveyed TreM and deadwood attributes, as well as structural and abiotic attributes, in 71 boreal old-growth forests situated in Quebec, Canada. We used hierarchical clustering analysis to identify TreM and deadwood abundance and diversity patterns in the studied stands. We identified five clusters of TreM and deadwood characteristics, which corresponded to three stages of old-growth forest succession: canopy break-up (beginning of the old-growth stage), transition old-growth stage (replacement of the first cohort by old-growth cohorts) and true old-growth stage (first cohort all or almost all gone). The peak in TreM richness and diversity was reached at the transition old-growth stage, whereas the peak for deadwood richness and diversity was reached at the true old-growth stage. Overall, true old-growth forests were defined by a combination of moderate to high TreM density and high deadwood volume, but these values significantly varied among stands depending on past secondary disturbances, stand structure and its composition (black spruce [Picea mariana Mill.] dominated vs mixed black spruce – balsam fir [Abies balsamea (L.) Mill.]). These results therefore underscore the importance of considering old-growth forests as dynamic rather than static ecosystems, as the composition of tree- and deadwood-related microhabitats in the same old-growth stand may markedly change over time. At landscape scale, these results also imply that the mosaic of habitats present in old-growth forests can vary greatly from one location to another, highlighting the importance of maintaining a diversity of old-growth forest structure and composition.
... Given that we use the 1970-2000 period, which is likely not representative of the temperatures experienced during early life stages of old trees, our temperature variable is more of an index of relative temperature across the study region. Finally, there are several broad-scale differences between the Balkan and Carpathian study sites that may influence tree growth and longevity, including higher annual precipitation and temperature in the Balkan region, as well as differences in bedrock (Kozák et al., 2018); we therefore included raw values of latitude for each plot to further explore if there are differences in life span across the region. ...
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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.
... For example, some groups described a crack as an item longer than 25 cm and deeper than 2 cm (Vuidot et al., 2011), others as an item longer than 100 cm (Kraus et al., 2016). Some groups used very detailed TreM types, for example, they distinguished cavities by size and wood decay class (Kozák et al., 2018), while other research groups used broader TreM types . ...
Article
The retention of trees bearing tree‐related microhabitats (TreMs) has become an important means of conserving biodiversity in production forests. However, we lack estimates of TreM formation rates and evidence on factors driving TreM formation. Based on the observation of 80,099 living trees from 19 species groups in Europe and Iran, we estimated the probability of TreM occurrence on trees and the associated rate of first TreM formation as a function of tree DBH, management, tree species group and random site effects. We built a separate model for each of 11 TreM groups. The hazard rate of first TreM formation (defined as the probability of formation of a first TreM forming on a tree that is known to have none, during an infinitesimal DBH increment) increased with DBH for some TreM groups like breeding‐woodpecker‐hole, rot‐hole or root‐concavity, indicating an acceleration in TreM formation during tree growth. However, it decreased with DBH for TreM groups like bark‐loss or dendrotelm, indicating slower formation on very large trees. Most TreM groups had reduced formation rates in managed forests (last logging less than 100 years ago) compared to unmanaged forests (no logging for at least 100 years), with the exception of dendrotelms. No general difference appeared between broadleaves and conifers but early‐successional species tended to have different TreMs than mid‐ and late‐successional species. Abies, Alnus, Betula, Fagus, Prunus, Quercus, Sorbus, Tilia and Ulmus displayed high formation rates for six TreM groups or more. Variability among sites was considerable. Synthesis and applications: The rate of formation of tree related microhabitats (TreMs) varies greatly among TreM groups, tree species, locations, tree diameters at breast height and forest management. The high rate of formation of some TeM groups on small trees implies that tree retention for biodiversity should concern trees of all sizes and start as soon as thinning operations have occurred. Biodiversity conservation should value not only forest stands and trees that already have many TreMs, but also those where the likelihood of future TreM formation is high due to species, maturity or local environmental conditions. The addition of quantitative models of TreM formation to forest stand dynamics simulators is necessary to better take into account biodiversity conservation in forest management.
... Naturally, the spatial density of tree-related microhabitats in forests is very high: according to studies in the Romanian and Ukrainian Carpathians and in the Dinaric Alps (commarmot et al. 2013;KozáK et al. 2018), one in three or even one in two trees in natural forests supports microhabitats. In these mixed forests dominated by deciduous trees there was an average of more than 400 TreMs/ha. ...
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Biodiversity is of great importance for the functioning of the forest ecosystem. Habitat trees are a key component of forest biodiversity. Experts from Europe have developed a typology of tree-related microhabitats, small life-sites borne by some trees, which are indispensable for thousands of specialised organisms. The uniform use of the forms, groups and types of these tree-related microhabitats facilitates the implementation of recommendations in forestry practice. In addition, these standardised data can be used for monitoring forest biodiversity or for evaluating the success of measures to promote biodiversity in forests.
... Es existiert bisher nur eine begrenzte Anzahl an Forschungsarbeiten.Waldbestände, die sich aus verschiedenen Baumarten zusammensetzen, sind weniger anfällig gegenüber abiotischen und biotischen Störungen. Darüber hinaus wirkt sich eine hohe Baumartenvielfalt auf regionaler Ebene positiv auf das Vorkommen und die Vielfalt an Baum-Mikrohabitaten aus12,13 .Die Baumartenvielfalt beeinflusst die Entwicklung verschiedener Gemeinschaften von Makropilzen. Die Anzahl holzzersetzender Makropilze steigt mit der Anzahl an vorkommenden Baumarten auf Bestandesebene14 . ...
... Another factor enhancing the richness and density of TreMs is the species diversity of the trees in a stand (Ouin et al., 2015;Kozák et al., 2018), because each species often has its own specific set of TreMs . Willow-Poplar riparian forests are spatially highly diverse: this is manifested by the mosaic of fairly small patches dominated mostly by various species of poplars and willows (Matuszkiewicz, 2001b ...
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Tree-related microhabitats (TreMs) are among the most important structural components of a forest, and have a significant impact on biodiversity and influence ecosystem functioning. Although forests that depend on natural lowland water regimes are severely endangered worldwide, and floodplain forests are considered to be the most complex and biologically rich habitats in the temperate zone, the TreMs in them have yet to be identified. This study investigates the assemblage of TreMs in natural Willow-Poplar riparian forests and analyses the environmental factors that influence their qualitative and quantitative compositions. A total of 90 sample plots (0.05 ha each) were selected at random in old-growth riparian forests that occur along a large unregulated river, the Vistula (Poland). A total of 62 TreM types were identified with a mean number of 16.0 ± 4.6 SD TreM types per plot and a mean density of 829.4 ± 360.1 SD TreM-bearing trees ha⁻¹. The number of TreMs found on an individual tree depends on its diameter, the number of trunks, its living status (living vs. dead tree) and the species it belongs to. The richness, density and diversity of TreMs found on a plot depends on the density of living trees, the basal area of living or dead trees, the number of tree species, and the percentage of Willows Salix sp. or of multi-trunk trees. Our study records for the first time the assemblage of TreMs in natural Willow-Poplar riparian forests and provides a reference for floodplain habitats. The results indicate that multi-species forests influenced by natural waterflow-related disturbances are hot-spots of TreM richness and abundance, and highlight the urgent need for the protection or restoration of these vanishing habitats.
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Popularnonaukowa monigrafia zagadnień związanych z bilansem, rolą i ochroną martwych drzew w w ekosystemach, głównie (ale nie tylko) leśnych. Przedstawia m. in. zagadnienia: Co to jest drewno. Jakich rozmiarów dorastają i jak długo żyją drzewa? Pochodzenie, bilans i cechy martwego drewna, w lasach, poza lasem: w parkach, zadrzewieniach i innych środowiskach; w wodach. Martwe drewno na żywym drzewie – Mikrosiedliska nadrzewne. Znikający krajobraz ekotonów leśnych i lasów pastwiskowych. Etapy i konsekwencje zamierania drzew. Jak martwe drzewa „ożywają”: kolonizacja martwych drzew i martwego drewna Zamierające i martwe drewno jako środowisko życia. Organizmy zwiąane z martwym drewnem. Funkcje ekosystemowe martwego drewna: Leśne „paliwo”, magazynowanie materii organicznej, akumulacja węgla i azotu, magazynowanie wody, rola martwych drzew w odnowieniu lasu, ochrona przed erozją, rola w procesach glebowych, rola w ciekach. Rola martwego drewna w ochronie lasu i ochronie przyrody. Rola w leśnictwie i świadomość leśników. Martwe drewno jako składnik chronionych ekosystemów i wskaźnik ich stanu. Ochrona gatunkowa zwiążanych z martwym drewnem zwierząt, roślin i grzybów, w tym gatunków reliktowych. Rozległe zaburzenia – niechciany dar przyrody? Martwe drewno a zagadnienia bezpieczeństwa. Martwe drewno w nauce i gospodarce. Metody jakościowej i ilościowej oceny martwego drewna. „Drugie Zycie Drzewa”, autorstwa J.M. Gutowskiego, A. Bobca, P. Pawlaczyka i K. Zuba ukazało się po raz pierwszy w 2004 r. Obecne II wydanie (2022 r.) jest znacznie zmienione i rozbudowane, stosownie do obecnej wiedzy na temat ekologicznej roli martwych drzew. Wiedza ta przez 18 lat jakie minęły od I wydania, wzrosła niepomiernie: w 2021 r. internetowe wyszukiwarki literatury naukowej znajdowały ok. 40 tys. publikacji na ten temat. Blisko połowa z nich pochodzi z ostatniego dziesięciolecia. Do autorów II wydania dołączyli: Michał Ciach i Anna Kujawa. W szczególności szeroko zostały opisane zagadnienia związane z rolą tzw. drzew biocenotycznych i mikrosiedlisk nadrzewnych w lasach. Zupełnie nową treść i jakość uzyskały rozdziały opisujące grzyby, porosty i śluzowce oraz ich związki z martwym drewnem. O nowe zagadnienia i treści został rozszerzony rozdział „Martwe drewno w ochronie lasu i ochronie przyrody”, który zaktualizowano też do obecnego stanu prawnego. Znacznie szerzej przedstawiono rolę martwego drewna w wodach. Zaktualizowano oraz uzupełniono, przede wszystkim o nową literaturę, również pozostałe rozdziały publikacji. Znacznie rozbudowano materiał ilustracyjny. Nowe wydanie liczy ponad 340 stron, dodatkowo na większym formacie, co oznacza ok. dwukrotnie większą objętość od wydania I. Książka w wersji elektronicznej (pdf) jest dostępna także na stronach wydawcy (The book is available at the publisher website): https://www.wwf.pl/sites/default/files/2022-03/drugie-zycie-drzewa-03-2022.pdf
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Forests are undergoing through a slow but steady process of forest area change, which happen to be different across countries. Predictions of future scenarios highlight the role of agriculture in shaping land-use change in Europe, with possible local benefits for forests. Thus, the role of management in shaping the forests of the future will increase according to the World’s demand for timber, clean water, biodiversity, clean air and other ecosystem services. Research is testing and developing new management strategies to halt completely biodiversity loss. The threats faced by biodiversity in managed forests constitute the challenges of future forest ecological research. The response of birds to environmental changes is a consequence of the close-knit species-habitat relationships they evolved and are adapted to. Adaptations to the forest environment are structural, behavioural and physiological. The alteration of the forest structures and their spatial allocation across landscapes creates threats to bird populations that need to be taken into account in conservation-oriented forest management. The present thesis aims to assess the numerical response of the bird assemblage to forest structures and its relevance for management. The general aim is focused on close-to-nature forest management and on the retention of structural elements as a conservation tool. The numerical response of the bird assemblage is investigated in terms of species diversity and abundance. The general aim is achieved by focusing on the following research questions: i. Which forest and landscape characteristics best explain the abundance and diversity of forest birds? ii. Which management practices can be developed for the conservation of birds in managed forests? This thesis is carried out within the framework of the ConFoBi Research Training Group (Conservation of Forest Biodiversity in multiple-use landscape of Central Europe). ConFoBi assesses whether and how structural retention measures contribute to the conservation of forest biodiversity in multiple-use landscapes of the temperate zone. The research programme of the present thesis has been implemented in the southern Black Forest, Germany, as a model system for temperate forests. The Black Forest is a forest-dominated low mountain range within a multiple-use landscape typical of central Europe, where 135 quadratic 1-ha-plots where selected within the forested areas. Plots were selected along two major environmental gradients: forest vertical complexity, represented by the number of standing dead trees found in each plot; landscape composition, represented by the amount of forest cover within 25 km2 surrounding each plot. All plots were inventoried by measuring the diameter of every tree (above 7 cm diameter at breast height) and the amounts of laying and standing dead wood. Because habitat trees are an important structural element in retention approaches, for each study plot the 15 largest trees were mapped and their existing microhabitats (such as hollows, cracks, and cavities) quantified. Landscape patterns were described using a range of metrics, including amount of forest cover and landscape metrics. Bird data were collected by employing point counts performed at the centre of each plots and repeated two or three times per sampling season (2017-2018). Abundance and diversity of birds were analysed using hierarchical N-mixture models and generalized linear (mixed) models, respectively. The results highlight that current retention practices are well below the retention levels needed by the bird assemblage to have abundance and diversity similar to those of unharvested forests, assessing the levels around 40-60% of retained trees. Retention practices can, however, be improved by retaining trees of higher ecological importance. Trees with a diameter 20 cm larger than the surrounding trees, with cavities, rot holes or concavities can potentially fulfill the habitat requirments of a large array of species, including woodpeckers and the related cavity-users community. The presence of those trees across the landscape can ensure the continuity of resources, while favouring more natural tree species composition will benefit bird species diversity. The response of the entire bird assemblage to the configuration of forest patches indicates that in landscapes with less aggregated forest patches, the abundance of the bird assemblage can potentially be lower than in landscapes with closer forest patches. I conclude that the establishment and assemble of the bird community is a hierarchical spatial process. Small environmental elements determine the occurrence and observed abundance of populations. The location of such elements determines which species and how many individuals of each species are found across the landscape. Over the entire landscape, the amount of available habitat and its configuration determines how many species can be found at a given site. Therefore, I suggest a hierarchical set of actions should be considered, each benefiting birds at different levels of biological organization and spatial scale. Actions to preserve forest area and avoid fast land-use changes should have higher priority. The provisioning of large trees and deadwood would then ensure that the forests retain those structures and functions that support the establishment of bird populations in optimal habitats.
Article
Given the global intensification of forest management and climate change, protecting and studying forests that develop free of direct human intervention-also known as primary forests-are becoming increasingly important. Yet, most countries still lack data regarding primary forest distribution. Previous studies have tested remote sensing approaches as a promising tool for identifying primary forests. However, their precision is highly dependent on data quality and resolution, which vary considerably. This has led to underestimation of primary forest abundance and distribution in some regions, such as the temperate zone of Europe. Field-based inventories of primary forests and methodologies to conduct these assessments are inconsistent; incomplete or inaccurate mapping increases the vulnerability of primary forest systems to continued loss from clearing and land-use change. We developed a comprehensive methodological approach for identifying primary forests, and tested it within one of Europe's hotspots of primary forest abundance: the Carpathian Mountains. From 2009 to 2015, we conducted the first national-scale primary forest census covering the entire 49,036 km 2 area of the Slovak Republic. We analyzed primary forest distribution patterns and the representativeness of potential vegetation types within primary forest remnants. We further evaluated the conservation status and extent of primary forest loss. Remaining primary forests are small, fragmented, and often do not represent the potential natural vegetation. We identified 261 primary forest localities. However, they represent only 0.47% of the total forested area, which is 0.21% of the country's land area. The spatial pattern of primary forests was clustered. Primary forests have tended to escape anthropogenic disturbance on sites with higher elevations, steeper slopes, rugged terrain, and greater distances from roads and settlements. Primary forest stands of montane mixed and subalpine spruce forests are more abundant compared to broadleaved forests. Notably, several habitat types are completely missing within primary forests (e.g., floodplain forests). More than 30% of the remaining primary forests are not strictly protected, and harvesting occurred at 32 primary forest localities within the study period. Almost all logging of primary forests was conducted inside of protected areas, underscoring the critical status of primary forest distribution in this part of Europe. Effective conservation strategies are urgently needed to stop the rapid loss and fragmentation of the remaining primary forests. Our approach based on precise, field-based surveys is widely applicable and transferrable to other fragmented forest landscapes.
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Purpose of the Review The concept of tree-related microhabitats (TreMs) is an approach to assess and manage multi-taxon species richness in forest ecosystems. Owing to their provision of special habitat features, TreMs are of special interest as a surrogate biodiversity indicator. In particular, in retention forestry, TreMs have gained attention over the past decade as a selection criterion for retained structural elements such as habitat trees. This review seeks to (a) address the suitability of TreMs as biodiversity indicator in the context of retention forestry, (b) summarize drivers of TreM occurrence and the status quo of the implementation of TreM-based retention concepts in forest management, and (c) discuss current and future challenges to the use of TreMs as biodiversity indicator. Recent Findings The TreM concept originated in Europe where it is now increasingly implemented. Most studies of the quantity, quality, and diversity of TreMs are focused on tree species from this region, although it is increasingly applied in other contexts. In addition to tree species, tree dimensions and live status have been identified as the main drivers of TreM occurrence. One major remaining research challenge is to verify relationships between the occurrence and abundance of forest-dwelling species from different taxonomic groups and TreMs to improve the evidence basis of this concept and thus increase its integration in forest conservation approaches. Summary TreMs are not the “silver bullet” indicator to quantify biodiversity of forest dwelling species, but they provide an important tool for forest managers to guide the selection of habitat trees for the conservation of the associated biodiversity.
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Land-use change and habitat loss have profoundly disturbed the resource availability for many organisms in farmlands, including bees. To counteract the resulting decline of bees and to maintain their pollination service to crops, bee pollinator-friendly schemes have been developed. We assessed the most established bee pollinator-friendly schemes which mainly aim at enhancing the availability of floral food resources and, or, nesting sites. We found that the availability of non-floral resources was typically overlooked in these schemes, although more than 30% of bee species worldwide depend on non-floral resources. In this opinion paper, we call for more attention on the role of non-floral resources in such conservation schemes. In fact, at least two of the most species rich Apoidea families, the Apidae and Megachilidae, need non-floral resources for nest building, defence, protection and health. For example, resin is known to improve health and resistance to pests and pathogens in stingless bees and the western honey bee Apis mellifera. Beyond social bees, many solitary bee species, in particularly within the Euglossini, Centridini and Megachilidae, also use resin, leaf pieces, trichome secretions and other materials for the construction and protection of brood cells and the nest. Besides protection, non-floral resources can also provide alternative food resources for bees, e.g. sugary secretions from other insects. Surprisingly little is known on this insect–insect interaction although some studies suggest that honey production by beekeepers can largely depend on this alternative food resource. The apparent knowledge gap on the role of non-floral resources for bees can thus directly concern stakeholders. Interestingly, many non-floral resources are provided by woody vegetation, but most of the bee pollinator-friendly schemes are currently orientated towards enhancing flower availability in field margins and flower strips. We therefore suggest more attention in the protection of trees and hedgerows in conservation, restoration and management schemes to best supporting bee health by providing combined access to nesting, floral and non-floral foraging resources.
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Die Biodiversität ist für das Funkti­onieren des Waldökosystems von grosser Bedeutung. Habitatbäume sind eine Schlüsselkompo­nente der Waldbiodiversität. Fach­leute aus Europa erarbeiteten eine Typologie der Lebensräume (soge­nannte Baummikrohabitate), die auf Bäumen vorkommen und für Tau­sende von spezialisierten Lebewe­sen unentbehrlich sind. Dieses Merkblatt beschreibt eine standardisierte Inventurmethode für Baummikrohabitate und Habitatbäume, die in allen gemässigten und mediterranen europäischen Wäldern anwendbar ist.
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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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The expected future intensification of forest disturbance as a consequence of ongoing anthropogenic climate change highlights the urgent need to more robustly quantify associated biotic responses. Saproxylic beetles are a diverse group of forest invertebrates representing a major component of biodiversity that is associated with the decomposition and cycling of wood nutrients and carbon in forest ecosystems. Disturbance-induced declines or shifts in their diversity indicate the loss of key ecological and/or morphological species traits that could change ecosystem functioning. Functional and phylogenetic diversity of biological communities is commonly used to link species communities to ecosystem functions. However, our knowledge on how disturbance intensity alters functional and phylogenetic diversity of saproxylic beetles is incomplete. Here, we analyzed the main drivers of saproxylic beetle abundance and diversity using a comprehensive dataset from montane primary forests in Europe. We investigated cascading relationships between 250 years of historical disturbance mechanisms, forest structural attributes and the taxonomic, phylogenetic and functional diversity of present-day beetle communities. Our analyses revealed that historical disturbances have significant effects on current beetle communities. Contrary to our expectations, different aspects of beetle communities, that is, abundance, taxonomic, phylogenetic and functional diversity, responded to different disturbance regime components. Past disturbance frequency was the most important component influencing saproxylic beetle communities and habitat via multiple temporal and spatial pathways. The quantity of deadwood and its diameter positively influenced saproxylic beetle abundance and functional diversity, whereas phylogenetic diversity was positively influenced by canopy openness. Analyzing historical disturbances, we observed that current beetle diversity is far from static, such that the importance of various drivers might change during further successional development. Only forest landscapes that are large enough to allow for the full range of temporal and spatial patterns of disturbances and post-disturbance development will enable long-term species coexistence and their associated ecosystem functions.
Book
Les arbres-habitats sont des arbres morts ou vivants, très gros et très âgés, portant des microhabitats. Ils sont d’une importance capitale pour la flore et la faune forestières spécialisées. Si les arbres-habitats sont courants dans les forêts inexploitées, ils nécessitent une attention particulière dans les forêts exploitées. Les arbres présentant des cavités comptent parmi les arbres-habitats les plus importants pour la faune et la flore forestières. Les vieilles cavités contenant du terreau abritent plusieurs des espèces de coléoptères forestiers les plus menacées. La gestion axée sur la protection des éléments naturels, dont les arbres- habitats, renforce les services écologiques, de plus en plus appréciés par la société. Les stratégies de gestion efficaces comprennent la mise en place d’« îlots de sénescence » au niveau des unités de gestion, associée à la conservation, lors de l’exploitation, d’arbres-habitats, à l’échelle du peuplement. Même si cela semble incompatible avec les intérêts économiques, il est essentiel de mettre en place un réseau d’arbres et de peuplements destinés à n’être jamais coupés, afin d’assurer les besoins minimums en habitat des espèces sensibles à l’exploitation. La continuité de la disponibilité en peuplements sénescents, en bois mort et en diverses structures forestières, semble également jouer un rôle important dans la préservation de la biodiversité forestière. Les microhabitats pourraient également être utilisés comme indicateurs de la biodiversité des forêts européennes. Il conviendrait d’établir une liste claire des caractéristiques des arbres-habitats, afin d’aider au dénombrement et au suivi des microhabitats et de les corréler à des niveaux de biodiversité.
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Background Tree-related microhabitats (hereafter, “TreMs”) are key components of forest biodiversity but they are still poorly known in North American hardwood forests. The spatial patterns of living trees bearing TreMs (hereafter, “TreM-trees”) also remain to be determined. As logging practices can lead to a loss of TreM-trees and of their associated biodiversity, it is essential to identify the factors explaining TreM occurrence to better integrate them into forest management. We therefore inventoried TreMs in 4 0.5-ha survey strips in northern hardwood forests in Quebec, Canada, while recording the spatial location of each tree. Two strips were located in unmanaged old-growth forests, and 2 were in forests managed under selection cutting. All 4 stands were dominated by sugar maple ( Acer saccharum Marsh.) and American beech ( Fagus grandifolia Ehrn.). Beech bark disease, an exotic pathology, was observed in all the strips. Results Large diameter at breast height and low tree vigor were the main characteristics explaining the presence of TreMs at the tree scale. TreM-trees presented slight spatial aggregation patterns. These aggregates, however, were not well-defined and were generally constituted by a large number of trees bearing few different types of TreMs. Two TreM classes (broken branch or top and woodpecker lodge) also presented a spatial aggregation. Logging practices had no significant effect on TreM occurrence. Beech bark disease increased the frequency of senescent beeches. The impact of this pathology on TreMs was however mitigated by the small size of infected trees and probably by the short time elapsed since its appearance. Conclusion The factors explaining the presence and abundance of TreMs on trees has so far been little studied in North American hardwood forests. Our results highlight that TreM-tree characteristics in the surveyed forests are consistent with those of previous studies conducted in other forest types and regions (e.g., Europe or Northwestern America). To our knowledge, this study is also the first to identify a spatial aggregation of TreM-trees and of specific TreM classes. It will be nevertheless necessary to determine whether the small impact of logging activities we observed results from current or past management practices.
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Evaluating the diversity and ecological value of habitat trees is an indicator for assessing biodiversity in forest ecosystems. This research was carried out to assess the ecological diversity and ecological value of microhabitats in the beech forests in the parcel 405 of Shir-Ghala, east of Guilan Province. Three plots with an area 1-ha were selected, and in each plot, all live trees and standing deadwood to explore each microhabitat, and their characteristics included the diameter at breast height, tree height as well as the number and type of microhabitat trees were recorded. To analyze the status of microhabitat diversity, alpha, beta and gamma diversity indices, Margalef richness index, Shannon-Wiener, and Simpson diversity indices, Pielou's evenness index was calculated. In total, microhabitats were identified on 87 habitat trees (equivalent to 24.2 microhabitats per 100 trees). The rarest form of microhabitat was woodpecker cavities and miocrosil, respectively. Trees with the holes comprised of woodpecker cavities, trunk cavities, main branch cavities, and buttress holes account for more than half of the total microhabitat (53%), and often located on live trees (68.6%) of oriental beech (77.3%). s found in the DBH class of 10-20 cm. In conclusion, it can be explained that the conservation and maintenance of habitat trees more than one meter in diameter is recommended to provide the microhabitat and preserve biodiversity in the forests.
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Tree microhabitats (cavities, conks of fungi, bark features) play an important role for both rare and specialized species biodiversity; their preservation should therefore be targeted by biodiversity-friendly forest practices. However, when compared to other old-growth characteristics like deadwood or large trees, tree microhabitats have only recently been studied so related scientific knowledge is still relatively limited. Defining target values for microhabitat densities in managed forests is mostly based on expert knowledge rather than quantitative empirical data.
Chapter
Both living and dead trees provide a number of distinct microhabitats for saproxylic species. By ‘microhabitats’ we mean discrete parts of a tree that host different species assemblages. Some of the microhabitats are only present in living trees, typically in mature or old individuals (Figure 7.1), and additional ones become available after the trees die. Wounds, rot holes and cavities; attached dead branches and roots; phloem (inner bark), sapwood and heartwood; fruiting bodies and mycelia of decomposer fungi etc. each host very different species assemblages. In this chapter, we describe in more detail the various dead-wood microhabitats, and the many ways in which saproxylic species can be dependent on their particular microenvironments. We present the microhabitats in the order in which they appear in a tree, starting from wounds and sap exudations that can occur even in young trees, followed by cavities and other microhabitats that develop as a result of decay in mature living trees, and ending with those microhabitats, such as subcortical space, that become available only after a tree has died. Some microhabitats, especially sap exudations and cavities, are far more common in broadleaved than in coniferous trees. Wounds and sap exudations in living trees Many factors can cause injuries to trees. Mechanical damage includes branch and stem breakages by wind, wounds made by falling trees hitting adjacent trees, lightning strikes, fire scars, frost cracks and snow breakage. Pathogenic fungi and bacteria can create necrotic patches, termed cankers, in the phloem layer. Most of the fungi that induce cankers kill the phloem and do not bring about sap flows. ‘Bleeding cankers’ are generally caused either by bacteria (Schmidt et al., 2008) or by Phytophthora species (Oomycetes) (Brown and Brasier, 2007) and produce only small amounts of exudates. Some vertebrate species, such as woodpeckers, and many invertebrate species can injure the bark, which may result in sap exudation and provide an opportunity for microbial colonization. For instance, cicadas (Hemiptera: Cicadidae) are known to cause sap exudation by piercing the bark with their stylet-like mouthparts to feed on sap (Yamazaki, 2007), and carpenterworm (Lepidoptera: Cossidae) larvae can initiate and maintain sap exudation by gnawing the bark (Yoshimoto and Nishida, 2007).