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Susanne Winter – One of the best experts on this subject based on the ideXlab platform.

  • Association of tree and plot characteristics with Microhabitat formation in European beech and Douglas-fir forests
    European Journal of Forest Research, 2015
    Co-Authors: Susanne Winter, Alexa K Michel, Josef Höfler, Andreas Böck, Donna P. Ankerst
    Abstract:

    Process-orientated, unmanaged forest remnants are not sufficient for halting the loss of forest biodiversity. Thus, integrated biodiversity-promoting management for forest inhabitants is needed. Microhabitats, such as tree cavities or bark pockets, are essential for the preservation of saproxylic species and of critical importance for endangered ones. This study investigates (1) which factors trigger the formation of Microhabitats at both the individual tree and aggregated plot level, and (2) whether the co-occurrence of Microhabitats differs between managed (=logged) and unmanaged forests. Relationships between the occurrence of 17 Microhabitat types and individual tree features (e.g. light availability, and tree vitality) and plot characteristics (e.g. stand density index and stand age) in 398 plots dominated by Fagus sylvatica or Pseudotsuga menziesii in Germany and the USA were studied using random-effects logistic and normal regression modelling. Separate analyses were performed for German beech forests, German Douglas-fir forests, and the US Douglas-fir forests. Our results show that (1) tree diameter in breast height (DBH), tree vitality and branchiness or epicormic branches are highly related with the occurrence of one or more Microhabitats on individual trees in managed and unmanaged beech and US Douglas-fir forests. In managed German Douglas-fir forests, vitality is not a predictor for the occurrence of Microhabitats on a tree, but tree density and the maximum age of trees in a stand in addition to DBH and branchiness have an effect. Time since last management is not a statistically significant predictor for the presence of Microhabitats at the tree level, but it is for German beech at the plot level. In Douglas-fir-dominated forests both in Germany and in the USA, the stand density index was the only common predictor at the plot level. (2) Unmanaged German beech and Douglas-fir forests exhibit more statistically significant and positive correlations with Microhabitat groups than managed stands, implying that the presence of one Microhabitat group on a tree is associated with the presence of other Microhabitat groups. We finally conclude that measures for supporting Microhabitat inhabitants in managed forests are scale and species dependent (tree versus plot level; beech versus Douglas-fir-dominated forests). Trees that carry Microhabitats seem to have similar features independently of forest management. At the plot level, density management may trigger the accumulation of Microhabitats. Our results indicate that in forest management, it is possible to consider the factors influencing the formation of Microhabitats and implement adequate forest practices to advance their formation.

  • tree Microhabitat structures as indicators of biodiversity in douglas fir forests of different stand ages and management histories in the pacific northwest u s a
    Forest Ecology and Management, 2009
    Co-Authors: Alexa K Michel, Susanne Winter
    Abstract:

    Abstract The importance of structural complexity in forest ecosystems for ecosystem diversity has been widely acknowledged. Tree Microhabitat structures as indicators of biodiversity, however, have only seldom been the focus of diversity research although their occurrence is highly correlated with the abundance of forest species and ecosystem functions. In this study, Microhabitat structures in Douglas-fir ( Pseudotsuga menziesii ) forests were defined and their frequency and abundance in natural stands and stands of varying active management histories and stand ages was compared. Indicator Microhabitat structures for natural forests were determined and the relationship of the abundance of Microhabitat structures with tree diameter of Douglas-fir trees was analysed. Most of the investigated Microhabitats are indeed indicators of natural mature and natural old-growth stands, e.g., broken tree top, bayonet top, crack or scar, bark loss, hollow chamber, stem cavity with decay, bark pocket with and without decay, bark bowl, burl, heavy resinosis, and bark burst. In Douglas-fir trees, resin drops and heavy resinosis were the dominant Microhabitats in trees with >20.0–40.0 cm diameter at breast height (dbh), whereas bark structures such as bowls in the bark, bark pockets, and bark pockets with decay were the most abundant Microhabitats in Douglas-fir trees >80.0 cm. Both management history (including no treatment in natural stands) and stand age determined the abundance of Microhabitats and Microhabitat composition of stands in our study. The observed Microhabitat variability was highest in stands that had not been harvested or otherwise treated silviculturally in many years (low treatment history) and the natural stands and lowest in the recently managed stands. Recently managed stands had, on average, 115 Microhabitats/ha, stands with a low treatment history had 520 Microhabitats/ha, and natural mature and natural old-growth stands had 745 Microhabitats/ha. Active management for Microhabitats in silviculturally-treated stands is important if the aim is to create structural complexity for a variety of organisms and ecosystem functions in even-aged Douglas-fir stands. Although the management of Microhabitats with respect to biodiversity and economic objectives often seem to be in conflict, we suggest silvicultural measures to reduce the current homogenization of forest stands with relatively minor losses of wood production especially if the reduced timber output is compared with the expected longterm social, economic, and ecological benefits. It may, however, take many decades to obtain stands that approximate the criteria for old-growth according to the interim minimum standards for old-growth Douglas-fir forests in their native western Washington and Oregon.

  • Microhabitats in lowland beech forests as monitoring tool for nature conservation
    Forest Ecology and Management, 2008
    Co-Authors: Susanne Winter, Georg Moller
    Abstract:

    Abstract We investigated the occurrence of 20 precisely defined structural Microhabitats on trees in mature (>120 years old) lowland beech forests in Germany that represented 12 managed, 5 recently unmanaged and 2 reference (>100 years unmanaged) stands. To promote naturalness assessments in forest inventories and for biodiversity monitoring, we analysed (1) which Microhabitats on individual trees are characteristic for reference stands, (2) the heterogeneity in types and frequency of Microhabitats, and (3) the link between structure-based indicators and threatened species of saproxylic beetles. The number and diversity of Microhabitats was significantly higher in the reference stands. We found there on average about 250 Microhabitats/ha with almost 7 of the total of 20 different Microhabitat types/circular plot of 500 m2. Fourteen individual Microhabitat types were significantly (P  Multi-habitat trees with up to seven different Microhabitat types on an individual tree were more common in the reference stands. We found a strong linear correlation between the number of Microhabitats and the dbh of the habitat tree in the references but not in the managed or recently unmanaged stands. Consequently, the architecture of large trees in the reference stands reflects the ecological continuity of these forests. We also analysed the frequency of threatened saproxylic beetles in relation to the presence of tree Microhabitats. Only recently unmanaged stands showed a clear correlation between the habitat supply with Microhabitats and the threatened saproxylic beetles. The number of threatened saproxylic beetles was high in the reference and low in the managed stands without a correlation with the number of Microhabitats. We propose that Microhabitats are a reliable monitoring tool for assessing and reporting on biodiversity of forests that naturally have a high structural heterogeneity and show examples for implementing Microhabitats into forest inventory and monitoring as a measure of nature conservation.

Yoan Paillet – One of the best experts on this subject based on the ideXlab platform.

  • Nothing else matters? Tree diameter and living status have more effects than biogeoclimatic context on Microhabitat number and occurrence: An analysis in French forest reserves
    PLoS ONE, 2019
    Co-Authors: Yoan Paillet, Frédéric Archaux, N. Debaive, Olivier Gilg, Eugenie Cateau, Eric Guilbert
    Abstract:

    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 biogeographical ranges. We used a nationwide database of forest reserves where Microhabitats 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 broadleaves 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 Microhabitats 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). Promoting large living and dead trees of several tree species may be a relevant, and nearly universal, way to favour Microhabitats and enhance the substrates needed to support specific biodiversity. In the future, a better understanding of Microhabitat drivers and dynamics at the tree scale may help to better define their role as biodiversity indicators for large-scale monitoring.

  • nothing else matters tree characteristics have more effects than biogeoclimatic context on Microhabitat diversity and occurrence a nationwide analysis
    bioRxiv, 2019
    Co-Authors: Yoan Paillet, Frédéric Archaux, N. Debaive, Olivier Gilg, Eugenie Cateau, Eric Guilbert
    Abstract:

    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 (cavities, cracks, conks of fungi) are tree-borne features that are reputed to support specific biodiversity for at least a part of species9 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 biogeographical ranges. We used a nationwide database of forest reserves where Microhabitats 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. Contrary to expectations, the total number of Microhabitat types per tree barely varied with tree genus – though we did find slightly higher accumulation levels for broadleaves than for conifers – nor did it vary with elevation or soil pH. 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 Microhabitats 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). Promoting large living and dead trees of several tree species may be an interesting, and nearly universal, way to favour Microhabitats and enhance the substrates needed to support specific biodiversity. In addition, a better understanding of Microhabitat drivers and dynamics at the tree scale may help to better define their role as biodiversity indicators for large-scale monitoring.

  • The indicator side of tree Microhabitats: a multi-taxon approach based on bats, birds and saproxylic beetles
    Journal of Applied Ecology, 2018
    Co-Authors: Yoan Paillet, Solène Du Puy, Frédéric Archaux, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, F. Gosselin, E. Guilbert
    Abstract:

    1. National and international forest biodiversity assessments largely rely on indirect indicators, based on elements of forest structure that are used as surrogates for species diversity. These proxies are reputedly easier and cheaper to assess than biodiversity. Tree Microhabitats – tree-borne singularities such as cavities, conks of fungi or bark characteristics – have gained attention as potential forest biodiversity indicators. However, as with most biodiversity indicators, there is a lack of scientific evidence documenting their quantitative link with the biodiversity they are supposed to assess. 2. We explored the link between Microhabitat indices and the richness and abundance of three taxonomic groups: bats, birds, and saproxylic beetles. Using a nation-wide multi-taxon sampling design in France, we compared 213 plots located inside and outside strict forest reserves. We hypothesized that the positive effect setting aside forest reserves has on biodiversity conservation is indirectly due to an increase in the proportion of large structural elements (e.g. living trees, standing and lying deadwood). These, in turn, are likely to favour the quantity and diversity of Microhabitats. We analysed the relationship between the abundance and species richness of different groups and guilds (e.g. red-listed species, forest specialists, cavity dwellers) and Microhabitat density and diversity. We then used confirmatory structural equation models to assess the direct and indirect effects of management abandonment, large structural elements and Microhabitats on the biodiversity of the target species. 3. For several groups of birds and bats, the indirect effect of management abandonment and large structural elements on biodiversity was mediated by Microhabitats. However, the magnitude of the link between Microhabitat indices and biodiversity was moderate. In particular, saproxylic beetles’ biodiversity was poorly explained by Microhabitats, large structural elements or management abandonment. 4. Synthesis and applications: Tree Microhabitats may serve as indicators for bats and birds, but they are not a universal biodiversity indicator. Rather, compared to large structural elements, they most likely have a complementary role to biodiversity. In terms of forest management and conservation, preserving diversity of Microhabitats at the local scale benefits several groups of both bats and birds.

F. Gosselin – One of the best experts on this subject based on the ideXlab platform.

  • The indicator side of tree Microhabitats: a multi-taxon approach based on bats, birds and saproxylic beetles
    Journal of Applied Ecology, 2018
    Co-Authors: Yoan Paillet, Solène Du Puy, Frédéric Archaux, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, F. Gosselin, E. Guilbert
    Abstract:

    1. National and international forest biodiversity assessments largely rely on indirect indicators, based on elements of forest structure that are used as surrogates for species diversity. These proxies are reputedly easier and cheaper to assess than biodiversity. Tree Microhabitats – tree-borne singularities such as cavities, conks of fungi or bark characteristics – have gained attention as potential forest biodiversity indicators. However, as with most biodiversity indicators, there is a lack of scientific evidence documenting their quantitative link with the biodiversity they are supposed to assess. 2. We explored the link between Microhabitat indices and the richness and abundance of three taxonomic groups: bats, birds, and saproxylic beetles. Using a nation-wide multi-taxon sampling design in France, we compared 213 plots located inside and outside strict forest reserves. We hypothesized that the positive effect setting aside forest reserves has on biodiversity conservation is indirectly due to an increase in the proportion of large structural elements (e.g. living trees, standing and lying deadwood). These, in turn, are likely to favour the quantity and diversity of Microhabitats. We analysed the relationship between the abundance and species richness of different groups and guilds (e.g. red-listed species, forest specialists, cavity dwellers) and Microhabitat density and diversity. We then used confirmatory structural equation models to assess the direct and indirect effects of management abandonment, large structural elements and Microhabitats on the biodiversity of the target species. 3. For several groups of birds and bats, the indirect effect of management abandonment and large structural elements on biodiversity was mediated by Microhabitats. However, the magnitude of the link between Microhabitat indices and biodiversity was moderate. In particular, saproxylic beetles’ biodiversity was poorly explained by Microhabitats, large structural elements or management abandonment. 4. Synthesis and applications: Tree Microhabitats may serve as indicators for bats and birds, but they are not a universal biodiversity indicator. Rather, compared to large structural elements, they most likely have a complementary role to biodiversity. In terms of forest management and conservation, preserving diversity of Microhabitats at the local scale benefits several groups of both bats and birds.

  • The indicator side of tree Microhabitats: a multi-taxonomic approach
    , 2017
    Co-Authors: Yoan Paillet, Solène Du Puy, Frédéric Archaux, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, F. Gosselin, E. Guilbert
    Abstract:

    Forest biodiversity assessment relies mostly on indirect indicators based on elements of forest structure used as a surrogate for species. However, most of those indirect indicators used in national and international evaluation processes lack scientific evidence documenting their quantitative link with the biodiversity they are supposed to assess. In addition, those for which the link is established generally concern only one taxon and are rarely considered at the community level. In this context, tree Microhabitats – defined as tree-borne singularities such as cavities, conks of fungi or bark characteristics – have recently gained attention as a potential forest biodiversity indicator for species that depend on them for at least a part of their life cycle and that are difficult to detect. However, like most other potential indicators, precise quantitative information on the link between biodiversity indices and Microhabitat variables remains scarce. We explored the link between the richness of three taxonomic groups (bats, birds, and saproxylic beetles) and Microhabitat indices using a nation-wide multi-taxonomic sampling design comparing 213 plots located inside and outside forest reserves. We hypothesized that the positive effect of setting aside forest reserves on biodiversity conservation was indirectly due to the increase in the proportion of large structural elements (living trees and standing deadwood) which in turn favoured the quantity and diversity of Microhabitats. We also hypothesized that Microhabitat indices would be better indicators than large and standing dead tree densities, two classical and often used indirect forest biodiversity indicators. We first analysed the response of total species richness and species richness of different groups and guilds (e.g. red-listed species, forest specialists, cavity dwellers…) to several Microhabitat indices (density, diversity) to identify the best Microhabitat metric. We then used confirmatory structural equation models to assess the indirect effects of management, large structural elements and Microhabitats on the diversity of the target species. We first showed that Microhabitat indices based on diversity better described biodiversity than indices based on abundance. Structural equation models confirmed that setting aside forest reserves increased the quantities of large trees and standing deadwood, which in turn drove higher quantities and diversity of Microhabitats. This significantly increased the richness of several taxonomic groups including notably total richness and cavity dweller richness of both birds and bats. However the magnitude of the link between Microhabitat indices and species richness was relatively small. Conversely, the biodiversity of saproxylic beetles was not driven by Microhabitat indices and, for this taxon only, models involving direct effects of large structural elements or management performed better. Tree Microhabitats appear to be an indicator for part of the taxonomic groups we analysed, but do not constitute a universal biodiversity indicator. They rather have a complementary role compared to large structural elements. Currently, their moderate correlation with biodiversity, as well as thei sensivity to other factors not taken into account in this study (e.g. observer effects), question their transferability to management and policy. Finally, this study calls for replicable and standardized multicriteria methods to validate biodiversity indicators.

  • Snags and large trees drive higher tree Microhabitat densities in strict forest reserves
    Forest Ecology and Management, 2017
    Co-Authors: Yoan Paillet, Frédéric Archaux, V. Boulanger, N. Debaive, Olivier Gilg, F. Gosselin, M. Fuhr, E. Guilbert
    Abstract:

    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. We compared the densities of Microhabitat-bearing trees between managed forests, where wood is still harvested, and strictly protected forest reserves, where harvesting has been abandoned, in 17 French forests (222 plots) located in both lowlands and mountain regions. We found that Microhabitat densities are generally higher in strict forest reserves than in managed forests and that this difference is mainly driven by standing dead and large living trees. Though scarce, standing dead trees over-contribute to the difference observed while large trees played a lesser but significant role. In addition, contrary to results obtained for other old-growth characteristics (such as deadwood volumes), the difference between managed and strict forest reserves was higher in mountain than in lowland forests. For individual Microhabitats, five out of eleven Microhabitats in mountains and only one in lowland (woodpecker cavities) were significantly more numerous in strict forest reserves than in managed forests. Finally, total Microhabitat density and density of specific Microhabitats such as cavities and bark features increased with time since the last harvest. This increase was also mainly supported by standing dead Microhabitat-bearing trees. Compared to previous studies in comparable contexts, the densities we estimated were generally higher; however, such comparisons could only be made for the most documented Microhabitat types. Our results support the idea that management abandonment favours the abundance and diversity of Microhabitats. However, Microhabitat dynamics remain poorly known and only long-term monitoring will help understand underlying mechanisms of recruitment. In the meantime, our results may inspire forest managers in their application of daily biodiversity-friendly practices.

Laurent Larrieu – One of the best experts on this subject based on the ideXlab platform.

  • Tree Microhabitats at the stand scale in montane beech-fir forests: practical information for taxa conservation in forestry
    European Journal of Forest Research, 2014
    Co-Authors: Laurent Larrieu, Christophe Bouget, Alain Cabanettes, Antoine Brin, Marc Deconchat
    Abstract:

    Recent studies have highlighted the key role of tree Microhabitats in forest habitat complexity and have suggested using them as surrogates for local taxonomic biodiversity. However, few practical guidelines have been published to help foresters in managing Microhabitats at the stand scale. This paper provides scientific background information to help to develop such guidelines. We surveyed trees in nine long-unmanaged beech–fir forests to model tree Microhabitat occurrence and diversity at the tree level. Data were upscaled to a size range of tree cluster, i.e., at the tree population scale, by aggregating observed values of Microhabitat occurrence. Accumulation curves were used to estimate the minimum number of trees required to make all the Microhabitat types available. Two managed forests were then studied to quantify management effects on Microhabitats. Diameter at breast height (dbh) and tree species, respectively, explained 16 and 10 % of the variations in the number of Microhabitat-bearing trees, and 21 and 10 % for the number of Microhabitat types. Beech trees and firs with a dbh of less than dbh 50 and 65 cm, respectively, did not ensure the provision of all Microhabitat types. At least 20 ha of unmanaged forest were necessary to conserve all the Microhabitat types. Current management practices have reduced the number of Microhabitat-bearing beeches both by reducing the number of very large trees (dbh > 67.5 cm) and by tree selection within mid-size diameters. For fir, only the logging of very large trees (dbh > 62.5 cm) negatively affected Microhabitats. These figures may inspire guidelines for conservation-friendly forestry.

  • Les Microhabitats portés par les arbres : facteurs clés pour leur présence, impact de la gestion courante et biodiversité associée
    , 2013
    Co-Authors: Laurent Larrieu, Alain Cabanettes, Christophe Bouget
    Abstract:

    L’étude des forêts sub-naturelles permet d’identifier les facteurs clés de la présence des Microhabitats portés par les arbres (dendro-Microhabitats) : diamètre ou âge, arbre vivant vs arbre mort, arbres feuillus ou résineux. De façon générale, les feuillus portent plus fréquemment des dendro-Microhabitats que les résineux, seuls les très gros arbres portent tous les types de dendro-Microhabitats et les chandelles contribuent fortement à l’abondance des dendro-Microhabitats. L’exploitation forestière (exploitation des gros arbres, sélection des tiges) perturbe fortement l’offre naturelle en dendro-Microhabitats, avec un effet variable sur la densité totale de Microhabitats, mais une réduction systématique de la diversité de Microhabitats et un changement des proportions des différents Microhabitats. Après abandon de l’exploitation, le stock de bois mort se reconstitue plus vite que celui des dendro-Microhabitats. La biodiversité associée aux dendro-Microhabitats est assez bien connue à l’échelle du Microhabitat, mais les déterminants clés à l’échelle de l’arbre sont encore à l’étude.

  • Impact of silviculture on dead wood and on the distribution and frequency of tree Microhabitats in montane beech-fir forests of the Pyrenees
    European Journal of Forest Research, 2012
    Co-Authors: Laurent Larrieu, Alain Cabanettes, Antoine Delarue
    Abstract:

    In forest ecosystems, the level of biodiversity is strongly linked to dead wood and tree Microhabitats. To evaluate the influence of current forest management on the availability of dead wood and on the abundance and distribution of Microhabitats, we studied the volume and diversity of dead wood objects and the distribution and frequency of cavities, dendrothelms, cracks, bark losses and sporophores of saproxylic fungi in montane beech-fir stands. We compared stands unmanaged for 50 or 100 years with continuously managed stands. A total of 1,204 live trees and 460 dead wood objects were observed. Total dead wood volume, snag volume and Microhabitat diversity were lower in the managed stands, but the total number of Microhabitats per ha was not significantly different between managed and unmanaged stands. Cavities were always the most frequent Microhabitat and cracks the least frequent. Dendrothelm and bark loss were favored by management. Beech (Fagus sylvatica) carried many more Microhabitats than silver fir (Abies alba), especially cavities, dendrothelms and bark losses. Fir very scarcely formed dendrothelms. Secondary tree species played an important role by providing cracks and bark losses. The proportion of Microhabitat-bearing trees increased dramatically above circumference thresholds of 225 cm for beech and 215 cm for fir. Firs with a circumference of less than 135 cm did not carry Microhabitats. In order to conserve Microhabitat-providing trees and to increase the volume of dead wood in managed stands, we recommend conserving trees that finish their natural cycle over 10–20% of the surface area.

Alexa K Michel – One of the best experts on this subject based on the ideXlab platform.

  • Association of tree and plot characteristics with Microhabitat formation in European beech and Douglas-fir forests
    European Journal of Forest Research, 2015
    Co-Authors: Susanne Winter, Alexa K Michel, Josef Höfler, Andreas Böck, Donna P. Ankerst
    Abstract:

    Process-orientated, unmanaged forest remnants are not sufficient for halting the loss of forest biodiversity. Thus, integrated biodiversity-promoting management for forest inhabitants is needed. Microhabitats, such as tree cavities or bark pockets, are essential for the preservation of saproxylic species and of critical importance for endangered ones. This study investigates (1) which factors trigger the formation of Microhabitats at both the individual tree and aggregated plot level, and (2) whether the co-occurrence of Microhabitats differs between managed (=logged) and unmanaged forests. Relationships between the occurrence of 17 Microhabitat types and individual tree features (e.g. light availability, and tree vitality) and plot characteristics (e.g. stand density index and stand age) in 398 plots dominated by Fagus sylvatica or Pseudotsuga menziesii in Germany and the USA were studied using random-effects logistic and normal regression modelling. Separate analyses were performed for German beech forests, German Douglas-fir forests, and the US Douglas-fir forests. Our results show that (1) tree diameter in breast height (DBH), tree vitality and branchiness or epicormic branches are highly related with the occurrence of one or more Microhabitats on individual trees in managed and unmanaged beech and US Douglas-fir forests. In managed German Douglas-fir forests, vitality is not a predictor for the occurrence of Microhabitats on a tree, but tree density and the maximum age of trees in a stand in addition to DBH and branchiness have an effect. Time since last management is not a statistically significant predictor for the presence of Microhabitats at the tree level, but it is for German beech at the plot level. In Douglas-fir-dominated forests both in Germany and in the USA, the stand density index was the only common predictor at the plot level. (2) Unmanaged German beech and Douglas-fir forests exhibit more statistically significant and positive correlations with Microhabitat groups than managed stands, implying that the presence of one Microhabitat group on a tree is associated with the presence of other Microhabitat groups. We finally conclude that measures for supporting Microhabitat inhabitants in managed forests are scale and species dependent (tree versus plot level; beech versus Douglas-fir-dominated forests). Trees that carry Microhabitats seem to have similar features independently of forest management. At the plot level, density management may trigger the accumulation of Microhabitats. Our results indicate that in forest management, it is possible to consider the factors influencing the formation of Microhabitats and implement adequate forest practices to advance their formation.

  • tree Microhabitat structures as indicators of biodiversity in douglas fir forests of different stand ages and management histories in the pacific northwest u s a
    Forest Ecology and Management, 2009
    Co-Authors: Alexa K Michel, Susanne Winter
    Abstract:

    Abstract The importance of structural complexity in forest ecosystems for ecosystem diversity has been widely acknowledged. Tree Microhabitat structures as indicators of biodiversity, however, have only seldom been the focus of diversity research although their occurrence is highly correlated with the abundance of forest species and ecosystem functions. In this study, Microhabitat structures in Douglas-fir ( Pseudotsuga menziesii ) forests were defined and their frequency and abundance in natural stands and stands of varying active management histories and stand ages was compared. Indicator Microhabitat structures for natural forests were determined and the relationship of the abundance of Microhabitat structures with tree diameter of Douglas-fir trees was analysed. Most of the investigated Microhabitats are indeed indicators of natural mature and natural old-growth stands, e.g., broken tree top, bayonet top, crack or scar, bark loss, hollow chamber, stem cavity with decay, bark pocket with and without decay, bark bowl, burl, heavy resinosis, and bark burst. In Douglas-fir trees, resin drops and heavy resinosis were the dominant Microhabitats in trees with >20.0–40.0 cm diameter at breast height (dbh), whereas bark structures such as bowls in the bark, bark pockets, and bark pockets with decay were the most abundant Microhabitats in Douglas-fir trees >80.0 cm. Both management history (including no treatment in natural stands) and stand age determined the abundance of Microhabitats and Microhabitat composition of stands in our study. The observed Microhabitat variability was highest in stands that had not been harvested or otherwise treated silviculturally in many years (low treatment history) and the natural stands and lowest in the recently managed stands. Recently managed stands had, on average, 115 Microhabitats/ha, stands with a low treatment history had 520 Microhabitats/ha, and natural mature and natural old-growth stands had 745 Microhabitats/ha. Active management for Microhabitats in silviculturally-treated stands is important if the aim is to create structural complexity for a variety of organisms and ecosystem functions in even-aged Douglas-fir stands. Although the management of Microhabitats with respect to biodiversity and economic objectives often seem to be in conflict, we suggest silvicultural measures to reduce the current homogenization of forest stands with relatively minor losses of wood production especially if the reduced timber output is compared with the expected longterm social, economic, and ecological benefits. It may, however, take many decades to obtain stands that approximate the criteria for old-growth according to the interim minimum standards for old-growth Douglas-fir forests in their native western Washington and Oregon.