The Experts below are selected from a list of 13557 Experts worldwide ranked by ideXlab platform
M Cuke - One of the best experts on this subject based on the ideXlab platform.
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the wildlife picture index monitoring top trophic levels
Animal Conservation, 2010Co-Authors: Timothy G Obrien, J E M Baillie, L Krueger, M CukeAbstract:Although recent Biodiversity loss has been compared with cataclysmic mass extinctions, we still possess few Indicators that can assess the extent or location of Biodiversity loss on a global scale. The Convention on Biological Diversity (CBD) has mandated development of Indicators that can meet the needs of monitoring Biodiversity by 2010. To date, many Indicators rely on unwarranted assumptions, secondary data, expert opinion and retrospective time series. We present a new Biodiversity Indicator, the Wildlife Picture Index (WPI) that targets medium and large-sized terrestrial birds and mammals in forested and savannah ecosystems that. The WPI is a composite Indicator based on the geometric mean of relative occupancy estimates derived from camera trap sampling at a landscape scale. It has been designed to meet the needs of a CBD Indicator while avoiding many of the pitfalls that characterize some CBD Indicators. We present an example using 8 years of camera trap data from Bukit Barisan Selatan National Park, Indonesia to show that the WPI is capable of detecting changes in the rate of loss of Biodiversity, a key requirement of a CBD Indicator. We conclude that the WPI should be effective at monitoring top trophic levels in forest and savannah ecosystems using primary data and can fill the gap in knowledge about trends in tropical Biodiversity.
F. Gosselin - One of the best experts on this subject based on the ideXlab platform.
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The Indicator side of tree microhabitats: a multi-taxon approach based on bats, birds and saproxylic beetles
Journal of Applied Ecology, 2018Co-Authors: Yoan Paillet, Frédéric Archaux, F. Gosselin, Solène Du Puy, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, E. GuilbertAbstract: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.
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The Indicator side of tree microhabitats: a multi-taxonomic approach
2017Co-Authors: Yoan Paillet, Frédéric Archaux, F. Gosselin, Solène Du Puy, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, E. GuilbertAbstract: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.
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Tree species diversity and abundance as Indicators of understory diversity in French mountain forests: Variations of the relationship in geographical and ecological space
Forest Ecology and Management, 2014Co-Authors: C. Zilliox, F. GosselinAbstract:Trees are one of the main components of forest ecosystems; they modify resource levels (light, nutrients, water) that affect understory vegetation composition and diversity. Tree species diversity is used as a Biodiversity Indicator in various European and French monitoring schemes for sustainable forest management. Moreover, tree species basal area has been found to better indicate floristic Biodiversity than tree species richness or diversity. Herein we empirically check this finding by analyzing data from mountain spruce-fir forests in France with Bayesian statistical models. We insist on the magnitude of the relationship and its variation in geographical and ecological space. Our results indicate that both tree species abundance (based on cover or basal area) and tree species richness and dominance are good Indicators of some parts of understory vascular plant species richness. The effect of dendrometric Indicators on floristic Biodiversity varied among ecological groups and along ecological gradients such as aspect, soil acidity, region and altitude. As a result, plots with north-facing and south-facing slopes exhibited opposite relationships of species richness with tree species abundance, and so did plots located on acidic and basic sites. We discuss these results in light of other empirical results relating positive interactions between species and abiotic stress. Our study supports evaluating Biodiversity Indicators to determine when they actually have non-negligible relationships with Biodiversity, i.e. for which ecological groups and in which ecological contexts.
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Towards the validation of a new forest Biodiversity Indicator: observer effects on tree microhabitats censuses in a French unmanaged forest
2012Co-Authors: Yoan Paillet, P. Coutadeur, A. Vuidot, Frédéric Archaux, F. GosselinAbstract:A growing field of forest research deals with the improvement of forest Biodiversity Indicators. Validation of Biodiversity Indicators requires an analysis of their applicability, their range of validity and the magnitude of the correlation with the Biodiversity they are supposed to represent. In this process, assessing the magnitude of observer effect is an essential step. In this context, we tested observer effects (probability of detection, probability of invention/false detection) on the censuses of tree microhabitats related to woodpecker cavities, cracks and bark characteristics. Within two 0.5ha plots in a forest reserve that has not been harvested for at least 150 years, 14 observers visually observed microhabitats on 106 Oak (Quercus petraea and Q. robur) and Beech (Fagus sylvatica) trees. We compared the censuses of these observers with an independent consensual census using parametric and Bayesian statistics. The mean number of microhabitats per tree varied widely between observers from 1.4 to over 3. Only three observers reported a mean number of microhabitats per tree statistically equivalent to the consensual census. The probability of detection also varied between observers among microhabitats (from to 0 to 1) as well as the probability of invention (from 0 to 0.7). These results show that microhabitats censuses are particularly prone to observer effects and should be used with caution. Such strong observer effects raise the question of the relevance of microhabitats as Biodiversity Indicator. However, we recommend to control for observer effects by (i) multiplying the number of training sessions and consensual censuses; (ii) recording microhabitats with two observers whenever possible, but the efficiency of this method remains to be tested; (iii) planning the fieldwork so that the factors of interest are not merely confused with observer effects and; (iv) integrating observer identity in statistical models whenever analysing such data.
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Influence of tree characteristics and forest management on tree microhabitats
2011Co-Authors: Yoan Paillet, A. Vuidot, Frédéric Archaux, F. GosselinAbstract:Higher densities of tree microhabitats in unmanaged forests may explain Biodiversity differences with managed forests. To better understand the determinants of this potential Biodiversity Indicator, we studied the influence of tree characteristics on a set of tree microhabitats (cavities, cracks, bark features) on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality (living versus deadwood) and species. We show that unmanaged forests contained more trees likely to host microhabitats (large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve Biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.
Yoan Paillet - One of the best experts on this subject based on the ideXlab platform.
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The Indicator side of tree microhabitats: a multi-taxon approach based on bats, birds and saproxylic beetles
Journal of Applied Ecology, 2018Co-Authors: Yoan Paillet, Frédéric Archaux, F. Gosselin, Solène Du Puy, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, E. GuilbertAbstract: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.
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The Indicator side of tree microhabitats: a multi-taxonomic approach
2017Co-Authors: Yoan Paillet, Frédéric Archaux, F. Gosselin, Solène Du Puy, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, E. GuilbertAbstract: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.
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Towards the validation of a new forest Biodiversity Indicator: observer effects on tree microhabitats censuses in a French unmanaged forest
2012Co-Authors: Yoan Paillet, P. Coutadeur, A. Vuidot, Frédéric Archaux, F. GosselinAbstract:A growing field of forest research deals with the improvement of forest Biodiversity Indicators. Validation of Biodiversity Indicators requires an analysis of their applicability, their range of validity and the magnitude of the correlation with the Biodiversity they are supposed to represent. In this process, assessing the magnitude of observer effect is an essential step. In this context, we tested observer effects (probability of detection, probability of invention/false detection) on the censuses of tree microhabitats related to woodpecker cavities, cracks and bark characteristics. Within two 0.5ha plots in a forest reserve that has not been harvested for at least 150 years, 14 observers visually observed microhabitats on 106 Oak (Quercus petraea and Q. robur) and Beech (Fagus sylvatica) trees. We compared the censuses of these observers with an independent consensual census using parametric and Bayesian statistics. The mean number of microhabitats per tree varied widely between observers from 1.4 to over 3. Only three observers reported a mean number of microhabitats per tree statistically equivalent to the consensual census. The probability of detection also varied between observers among microhabitats (from to 0 to 1) as well as the probability of invention (from 0 to 0.7). These results show that microhabitats censuses are particularly prone to observer effects and should be used with caution. Such strong observer effects raise the question of the relevance of microhabitats as Biodiversity Indicator. However, we recommend to control for observer effects by (i) multiplying the number of training sessions and consensual censuses; (ii) recording microhabitats with two observers whenever possible, but the efficiency of this method remains to be tested; (iii) planning the fieldwork so that the factors of interest are not merely confused with observer effects and; (iv) integrating observer identity in statistical models whenever analysing such data.
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Influence of tree characteristics and forest management on tree microhabitats
2011Co-Authors: Yoan Paillet, A. Vuidot, Frédéric Archaux, F. GosselinAbstract:Higher densities of tree microhabitats in unmanaged forests may explain Biodiversity differences with managed forests. To better understand the determinants of this potential Biodiversity Indicator, we studied the influence of tree characteristics on a set of tree microhabitats (cavities, cracks, bark features) on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality (living versus deadwood) and species. We show that unmanaged forests contained more trees likely to host microhabitats (large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve Biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.
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Influence of tree characteristics and forest management on tree microhabitats
Biological Conservation, 2011Co-Authors: A. Vuidot, Yoan Paillet, Frédéric Archaux, F. GosselinAbstract:Higher densities of tree microhabitats in unmanaged forests may explain Biodiversity differences with managed forests. To better understand the determinants of this potential Biodiversity Indicator, we studied the influence of tree characteristics on a set of tree microhabitats (e.g. cavities, cracks, bark features)on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality and species. We show that unmanaged forests contained more trees likely to host microhabitats (i.e. large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve Biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (e.g. veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.
Timothy G Obrien - One of the best experts on this subject based on the ideXlab platform.
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the wildlife picture index a Biodiversity Indicator for top trophic levels
Biodiversity Monitoring and Conservation: Bridging the Gap between Global Commitment and Local Action, 2013Co-Authors: Timothy G Obrien, Margaret F KinnairdAbstract:Most conservationists agree that tropical regions harbor most of the Earth’s Biodiversity. Two of the most important biomes in the terrestrial tropics are the rainforests and the tropical savannas. Tropical rainforests occur in five major tropical regions, covering 6.25 million km2 (∼4.1% of the Earth’s land surface) and contain >50% of total Biodiversity, including the majority of birds and mammals. Tropical savannas occur in six major tropical regions covering 27.6 million km2 (∼18.5% of the Earth’s land surface) and, while less diverse than rainforests, they contain significant numbers of mammals and birds, especially the large iconic species. Forests and savannas face severe threats from the usual agents of Biodiversity loss including human population growth, biomass consumption for fuel, natural resource extraction, habitat loss, agricultural development, and climate change (Millennium Ecosystem Assessment, 2005). Recognizing the threats to the Earth’s Biodiversity, the Convention on Biological Diversity committed 190 countries to achieve a significant reduction in the rate of loss of Biodiversity by 2010 (Decision VI/26; CBD Strategic Plan). Along with this commitment came the realization that monitoring change in Biodiversity was an extremely complex issue, and that a toolkit of monitoring techniques was needed to track all the different components that make up our notion of Biodiversity (Dobson, 2005). As a first step to developing this toolbox, the CBD encouraged the compilation of existing datasets into composite Indicators to establish the baseline of knowledge about Biodiversity change and to track that change into the future. Problems with this
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the wildlife picture index monitoring top trophic levels
Animal Conservation, 2010Co-Authors: Timothy G Obrien, J E M Baillie, L Krueger, M CukeAbstract:Although recent Biodiversity loss has been compared with cataclysmic mass extinctions, we still possess few Indicators that can assess the extent or location of Biodiversity loss on a global scale. The Convention on Biological Diversity (CBD) has mandated development of Indicators that can meet the needs of monitoring Biodiversity by 2010. To date, many Indicators rely on unwarranted assumptions, secondary data, expert opinion and retrospective time series. We present a new Biodiversity Indicator, the Wildlife Picture Index (WPI) that targets medium and large-sized terrestrial birds and mammals in forested and savannah ecosystems that. The WPI is a composite Indicator based on the geometric mean of relative occupancy estimates derived from camera trap sampling at a landscape scale. It has been designed to meet the needs of a CBD Indicator while avoiding many of the pitfalls that characterize some CBD Indicators. We present an example using 8 years of camera trap data from Bukit Barisan Selatan National Park, Indonesia to show that the WPI is capable of detecting changes in the rate of loss of Biodiversity, a key requirement of a CBD Indicator. We conclude that the WPI should be effective at monitoring top trophic levels in forest and savannah ecosystems using primary data and can fill the gap in knowledge about trends in tropical Biodiversity.
Frédéric Archaux - One of the best experts on this subject based on the ideXlab platform.
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The Indicator side of tree microhabitats: a multi-taxon approach based on bats, birds and saproxylic beetles
Journal of Applied Ecology, 2018Co-Authors: Yoan Paillet, Frédéric Archaux, F. Gosselin, Solène Du Puy, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, E. GuilbertAbstract: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.
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The Indicator side of tree microhabitats: a multi-taxonomic approach
2017Co-Authors: Yoan Paillet, Frédéric Archaux, F. Gosselin, Solène Du Puy, Christophe Bouget, V. Boulanger, N. Debaive, Olivier Gilg, E. GuilbertAbstract: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.
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Towards the validation of a new forest Biodiversity Indicator: observer effects on tree microhabitats censuses in a French unmanaged forest
2012Co-Authors: Yoan Paillet, P. Coutadeur, A. Vuidot, Frédéric Archaux, F. GosselinAbstract:A growing field of forest research deals with the improvement of forest Biodiversity Indicators. Validation of Biodiversity Indicators requires an analysis of their applicability, their range of validity and the magnitude of the correlation with the Biodiversity they are supposed to represent. In this process, assessing the magnitude of observer effect is an essential step. In this context, we tested observer effects (probability of detection, probability of invention/false detection) on the censuses of tree microhabitats related to woodpecker cavities, cracks and bark characteristics. Within two 0.5ha plots in a forest reserve that has not been harvested for at least 150 years, 14 observers visually observed microhabitats on 106 Oak (Quercus petraea and Q. robur) and Beech (Fagus sylvatica) trees. We compared the censuses of these observers with an independent consensual census using parametric and Bayesian statistics. The mean number of microhabitats per tree varied widely between observers from 1.4 to over 3. Only three observers reported a mean number of microhabitats per tree statistically equivalent to the consensual census. The probability of detection also varied between observers among microhabitats (from to 0 to 1) as well as the probability of invention (from 0 to 0.7). These results show that microhabitats censuses are particularly prone to observer effects and should be used with caution. Such strong observer effects raise the question of the relevance of microhabitats as Biodiversity Indicator. However, we recommend to control for observer effects by (i) multiplying the number of training sessions and consensual censuses; (ii) recording microhabitats with two observers whenever possible, but the efficiency of this method remains to be tested; (iii) planning the fieldwork so that the factors of interest are not merely confused with observer effects and; (iv) integrating observer identity in statistical models whenever analysing such data.
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Influence of tree characteristics and forest management on tree microhabitats
2011Co-Authors: Yoan Paillet, A. Vuidot, Frédéric Archaux, F. GosselinAbstract:Higher densities of tree microhabitats in unmanaged forests may explain Biodiversity differences with managed forests. To better understand the determinants of this potential Biodiversity Indicator, we studied the influence of tree characteristics on a set of tree microhabitats (cavities, cracks, bark features) on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality (living versus deadwood) and species. We show that unmanaged forests contained more trees likely to host microhabitats (large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve Biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.
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Influence of tree characteristics and forest management on tree microhabitats
Biological Conservation, 2011Co-Authors: A. Vuidot, Yoan Paillet, Frédéric Archaux, F. GosselinAbstract:Higher densities of tree microhabitats in unmanaged forests may explain Biodiversity differences with managed forests. To better understand the determinants of this potential Biodiversity Indicator, we studied the influence of tree characteristics on a set of tree microhabitats (e.g. cavities, cracks, bark features)on 75 plots in managed and unmanaged French forests. We hypothesized that the number of different microhabitat types per tree and the occurrence of a given microhabitat type on a tree would be higher in unmanaged than in managed forests, and that this difference could be linked to individual tree characteristics: diameter, vitality and species. We show that unmanaged forests contained more trees likely to host microhabitats (i.e. large trees, snags) at the stand level. However, at the tree level, forest management did not influence microhabitats; only tree characteristics did: large trees and snags contained more microhabitats. The number and occurrence of microhabitats also varied with tree species: oaks and beech generally hosted more microhabitats, but occurrence of certain types of microhabitats was higher on fir and spruce. We conclude that, even though microhabitats are not equally distributed between managed and unmanaged forests, two trees with similar characteristics in similar site conditions have the same number and probability of occurrence of microhabitats, whatever the management type. In order to preserve Biodiversity, foresters could reproduce unmanaged forest features in managed forests through the conservation of specific tree types (e.g. veteran trees, snags). Tree microhabitats could also be more often targeted in sustainable forest management monitoring.