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Tord Snäll - One of the best experts on this subject based on the ideXlab platform.
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Local epiphyte establishment and future metapopulation dynamics in landscapes with different spatiotemporal properties
Ecology, 2017Co-Authors: Rocío Belinchón, Philip J. Harrison, Louise Mair, Gergely Várkonyi, Tord SnällAbstract:Understanding the relative importance of different ecological processes on the metapopulation dynamics of species is the basis for accurately forecasting metapopulation size in fragmented landscapes. Successful local Colonization depends on both species dispersal range and how local habitat conditions affect establishment success. Moreover, there is limited understanding of the effects of different spatiotemporal landscape properties on future metapopulation size. We investigate which factors drive the future metapopulation size of the epiphytic model lichen species Lobaria pulmonaria in a managed forest landscape. First, we test the importance of dispersal and local conditions on the Colonization–extinction dynamics of the species using Bayesian state-space modelling of a large-scale data set collected over a 10-yr period. Second, we test the importance of dispersal and establishment limitation in explaining establishment Probability and subsequent local population growth, based on a 10-yr propagule sowing experiment. Third, we test how future metapopulation size is affected by different metapopulation and spatiotemporal landscape dynamics, using simulations with the metapopulation models fitted to the empirical data. The Colonization Probability increased with tree inclination and connectivity, with a mean dispersal distance of 97 m (95% credible intervals, 5–530 m). Local extinctions were mainly deterministic set by tree mortality, but also by tree cutting by forestry. No experimental establishments took place on clearcuts, and in closed forest the establishment Probability was higher on trees growing on moist than on dry-mesic soils. The subsequent local population growth rate increased with increasing bark roughness. The simulations showed that the restricted dispersal range estimated (compared to non-restricted dispersal range), and short tree rotation length (65 yr instead of 120) had approximately the same negative effects on future metapopulation size, while regeneration of trees creating a random tree pattern instead of an aggregated one had only some negative effect. However, using the Colonization rate obtained with the experimentally added diaspores led to a considerable increase in metapopulation size, making the dispersal limitation of the species clear. The future metapopulation size is thus set by the number of host trees located in shady conditions, not isolated from occupied trees, and by the rotation length of these host trees.
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development of secondary woodland decreases epiphyte metapopulation sizes in wooded grasslands
Biological Conservation, 2014Co-Authors: Victor Johansson, Thomas Ranius, Tord SnällAbstract:Abandoned management of wooded grasslands leads to development of secondary woodland. We investigated how this development affects the Colonization–extinction dynamics and persistence of epiphytic lichens associated with old trees. We modelled Colonization Probability based on observed Colonizations (turnover data) during four years of two old-oak-associated lichens on 1236 oaks. Persistence was assessed by projections of future dynamics. We also used the turnover models to validate models fitted to snapshot data (from one point in time). Epiphyte Colonization probabilities were lower on trees in closed than in open conditions, and the probabilities increased with increasing connectivity to surrounding occupied trees. The additional four study species had too few Colonizations to be modelled, and thus, very low Colonization rates. Local extinctions occurred only deterministically through patch destruction processes. In projections of future metapopulation dynamics, when assuming that all trees were in closed conditions, the metapopulations decreased slowly; new equilibria had not been reached after 200 years. In contrast, when assuming open conditions for all trees, to test for effects of clearing vegetation around oaks in closed conditions, the metapopulations increased comparatively fast. The turnover models and the snapshot models, gave similar projections of metapopulation sizes, when assuming that the present level of secondary woodland remained constant over time. Development of secondary woodland in wooded grassland has negative impacts on epiphyte metapopulations. However, the slow metapopulation declines suggest that restoration will be successful. High priority should be given to resumed grazing and clearing vegetation around old trees, in particular close to dispersal sources.
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A model for non‐equilibrium metapopulation dynamics utilizing data on species occupancy, patch ages and landscape history
Journal of Ecology, 2014Co-Authors: Alejandro Ruete, Örjan Fritz, Tord SnällAbstract:Summary The distribution pattern of many species reflects the past rather than the current structure of landscapes. Consequently, species are most often not in equilibrium with the current landscape structure. Yet this is a well-known fact, there is no appropriate approach to estimate the Colonization rate of non-equilibrium species based on only data on the species occurrence pattern in the landscape. We present an approach to estimate the Colonization rate of non-equilibrium metapopulations. The approach requires only data on species presence/absence among its patches (occurrence pattern), data on patch ages and data on the historic distribution of the patches in the landscape. By estimating the past occurrence patterns and Colonization events leading to the current pattern of occupied and non-occupied patches, we estimate the Colonization rate, including the dispersal kernel. We also show how to estimate effects of local patch conditions and how to include an independent estimate of the local extinction rate based on other data. We use nine epiphytic lichen species confined to beech trees to illustrate the method. Five species had restricted dispersal range, between 200 and 4700 m, and their Colonization rate decreased with increasing fragmentation. Species Colonization rates were related to niche width. Among the demographic parameters, the force of Colonization was more important than the dispersal range in explaining the Colonization rates. Local patch conditions did not explain the Colonization Probability of any species. In metapopulation projections that did not account for restricted dispersal range, higher future metapopulation sizes were projected. Synthesis. The presented approach uses data on only species occurrence, patch age and landscape history to estimate the species Colonization rate and dispersal kernel. It can also utilize independent data on local extinction rate. Rather than identifying factors explaining the occurrence pattern, the model estimates the rate of change in the occurrence pattern. This dynamic modelling allows testing general and applied questions on the dynamics or viability of metapopulations of sessile species. The approach is applicable for species whose distribution pattern reflects the past rather than the current landscape structure, for example, certain epiphytes and ground-floor plants.
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edge creation and tree dieback influence the patch tracking metapopulation dynamics of a red listed epiphytic bryophyte
Journal of Applied Ecology, 2011Co-Authors: Jeanmichel Roberge, Stina Bengtsson, Soren Wulff, Tord SnällAbstract:1. Edges in landscapes have an effect on the abundance of many species but the underlying ecological mechanisms are poorly known for most taxonomic groups. One way to gain insight into the mechanisms is to examine how key demographic or metapopulation parameters are affected by proximity to edge. The main objective of this study was to investigate the effects of edge creation through clearcutting on the dynamics of forest species’ metapopulations. 2. We used the red-listed epiphytic moss Neckera pennata as a model species. Based on data from repeated surveys of a metapopulation and its host tree network in a hemiboreal forest, we tested the effect of edge creation on key metapopulation parameters: rates of local Colonization and extinction, local abundance growth and patch destruction through the fall of host trees. We predicted the long-term consequences of the edge effects using simulations with Bayesian statistical models. We also explored the potential effects of the pathogen Chalara fraxinea causing ash dieback, a tree disease currently spreading in Europe. 3. The Colonization Probability on host trees unoccupied by the moss increased with increasing connectivity to occupied trees. The growth of local populations on occupied trees decreased with increasing proximity to edge, and with initial local abundance. Stochastic extinctions of the epiphyte from standing trees were very rare and only occurred near the edge; most of the observed extinctions were deterministic due to tree fall. Tree fall decreased with increasing distance from the edge into the forest, and with increasing tree diameter. 4. Under edge conditions, simulations predicted decreases in the total number of host trees, number of occupied host trees, and in the total abundance of the epiphyte over a 30-year period. We suggest that ash dieback increases the tree fall rate and thereby the local extinction rate, leading to increased metapopulation extinction risk. 5. Synthesis and applications. The results show that small protected forest areas such as woodland key habitats may not allow long-term persistence of red-listed epiphytes if they are influenced by edge creation through clearcutting. Delineating uncut buffers of 50–100 m around the protected areas may alleviate such effects.
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Edge creation and tree dieback influence the patch‐tracking metapopulation dynamics of a red‐listed epiphytic bryophyte
Journal of Applied Ecology, 2011Co-Authors: Jeanmichel Roberge, Stina Bengtsson, Soren Wulff, Tord SnällAbstract:1. Edges in landscapes have an effect on the abundance of many species but the underlying ecological mechanisms are poorly known for most taxonomic groups. One way to gain insight into the mechanisms is to examine how key demographic or metapopulation parameters are affected by proximity to edge. The main objective of this study was to investigate the effects of edge creation through clearcutting on the dynamics of forest species’ metapopulations. 2. We used the red-listed epiphytic moss Neckera pennata as a model species. Based on data from repeated surveys of a metapopulation and its host tree network in a hemiboreal forest, we tested the effect of edge creation on key metapopulation parameters: rates of local Colonization and extinction, local abundance growth and patch destruction through the fall of host trees. We predicted the long-term consequences of the edge effects using simulations with Bayesian statistical models. We also explored the potential effects of the pathogen Chalara fraxinea causing ash dieback, a tree disease currently spreading in Europe. 3. The Colonization Probability on host trees unoccupied by the moss increased with increasing connectivity to occupied trees. The growth of local populations on occupied trees decreased with increasing proximity to edge, and with initial local abundance. Stochastic extinctions of the epiphyte from standing trees were very rare and only occurred near the edge; most of the observed extinctions were deterministic due to tree fall. Tree fall decreased with increasing distance from the edge into the forest, and with increasing tree diameter. 4. Under edge conditions, simulations predicted decreases in the total number of host trees, number of occupied host trees, and in the total abundance of the epiphyte over a 30-year period. We suggest that ash dieback increases the tree fall rate and thereby the local extinction rate, leading to increased metapopulation extinction risk. 5. Synthesis and applications. The results show that small protected forest areas such as woodland key habitats may not allow long-term persistence of red-listed epiphytes if they are influenced by edge creation through clearcutting. Delineating uncut buffers of 50–100 m around the protected areas may alleviate such effects.
Yves Souchon - One of the best experts on this subject based on the ideXlab platform.
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integrated modelling of functional and structural connectivity of river corridors for european otter recovery
Ecological Modelling, 2014Co-Authors: K Van Looy, Jeremy Piffady, Cyril Cavillon, Philippe Landry, Thierry Tormos, Yves SouchonAbstract:Abstract Connectivity may be structural , based on adjacency of landscape features, or functional , based on how that adjacency translates to movement of organisms. We present a modelling approach that elucidates both aspects of connectivity to identify vital corridors and conservation priorities in a river network. For the dendritic network structure of river systems, at first a graph theoretic structure is developed to model the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchical modelling of species dispersal is applied to infer the influence of riparian corridor characteristics to the species Colonization. The integration of the functional and structural component is realized with a graph-theoretic connectivity measure. With this approach, the European otter Colonization of the Loire river basin over 25 years is modelled on the basis of large datasets on riparian corridor land use and hydromorphological characteristics of a 17,000 km river network. Channel straightening and riparian forest fragmentation are determined to be key elements to the functional connectivity. Road infrastructure is distinguished as a critical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Integration of the Bayesian model posterior Colonization Probability in the integrated connectivity analysis reveals the importance of the river network density to the otter Colonization and locates conservation priorities mainly in the lower parts of the river basin. Synthesis and applications Both functional and structural connectivity are essential elements in the contexts of ecological network identification for species conservation and recovery. We successfully developed an integrated modelling of both components of connectivity that highlighted the importance of the downstream basin for a well-connected ecological network for the otter.
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integrated modelling of functional and structural connectivity of river corridors for european otter recovery
Ecological Modelling, 2014Co-Authors: K Van Looy, Jeremy Piffady, Cyril Cavillon, Philippe Landry, Thierry Tormos, Yves SouchonAbstract:Abstract Connectivity may be structural , based on adjacency of landscape features, or functional , based on how that adjacency translates to movement of organisms. We present a modelling approach that elucidates both aspects of connectivity to identify vital corridors and conservation priorities in a river network. For the dendritic network structure of river systems, at first a graph theoretic structure is developed to model the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchical modelling of species dispersal is applied to infer the influence of riparian corridor characteristics to the species Colonization. The integration of the functional and structural component is realized with a graph-theoretic connectivity measure. With this approach, the European otter Colonization of the Loire river basin over 25 years is modelled on the basis of large datasets on riparian corridor land use and hydromorphological characteristics of a 17,000 km river network. Channel straightening and riparian forest fragmentation are determined to be key elements to the functional connectivity. Road infrastructure is distinguished as a critical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Integration of the Bayesian model posterior Colonization Probability in the integrated connectivity analysis reveals the importance of the river network density to the otter Colonization and locates conservation priorities mainly in the lower parts of the river basin. Synthesis and applications Both functional and structural connectivity are essential elements in the contexts of ecological network identification for species conservation and recovery. We successfully developed an integrated modelling of both components of connectivity that highlighted the importance of the downstream basin for a well-connected ecological network for the otter.
Emanuel Fronhofer - One of the best experts on this subject based on the ideXlab platform.
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The downward spiral: eco-evolutionary feedback loops lead to the emergence of ‘elastic’ ranges
Ecography, 2016Co-Authors: Alexander Kubisch, Anna-marie Winter, Emanuel FronhoferAbstract:In times of severe environmental changes and resulting shifts in the geographical distribution of animal and plant species it is crucial to unravel the mechanisms responsible for the dynamics of species’ ranges. Without such a mechanistic understanding, reliable projections of future species distributions are difficult to derive. Species’ ranges may be highly dynamic. One particularly interesting phenomenon is range contraction following a period of expansion, referred to as ‘elastic’ behaviour. It has been proposed that this phenomenon occurs in habitat gradients, which are characterized by a negative cline in selection for dispersal from the range core towards the margin, as one may find, for example, with increasing patch isolation. Using individual‐based simulations and numerical analyses we show that Allee effects are an important determinant of range border elasticity. If only intra‐specific processes are considered, Allee effects are even a necessary condition for ranges to exhibit elastic behavior. The eco‐evolutionary interplay between dispersal evolution, Allee effects and habitat isolation leads to lower Colonization Probability and higher local extinction risk after range expansions, which result in an increasing amount of marginal sink patches and consequently, range contraction. We also demonstrate that the nature of the gradient is crucial for range elasticity. Gradients which do not select for lower dispersal at the margin than in the core (especially gradients in patch size, demographic stochasticity and extinction rate) do not lead to elastic range behavior. Thus, we predict that range contractions are likely to occur after periods of expansion for species living in gradients of increasing patch isolation, which suffer from Allee effects.
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The downward spiral: eco‐evolutionary feedback loops lead to the emergence of ‘elastic’ ranges
Ecography, 2015Co-Authors: Alexander Kubisch, Anna-marie Winter, Emanuel FronhoferAbstract:In times of severe environmental changes and resulting shifts in the geographical distribution of animal and plant species it is crucial to unravel the mechanisms responsible for the dynamics of species’ ranges. Without such a mechanistic understanding, reliable projections of future species distributions are difficult to derive. Species’ ranges may be highly dynamic. One particularly interesting phenomenon is range contraction following a period of expansion, referred to as ‘elastic’ behaviour. It has been proposed that this phenomenon occurs in habitat gradients, which are characterized by a negative cline in selection for dispersal from the range core towards the margin, as one may find, for example, with increasing patch isolation. Using individual-based simulations and numerical analyses we show that Allee effects are an important determinant of range border elasticity. If only intra-specific processes are considered, Allee effects are even a necessary condition for ranges to exhibit elastic behavior. The eco-evolutionary interplay between dispersal evolution, Allee effects and habitat isolation leads to lower Colonization Probability and higher local extinction risk after range expansions, which result in an increasing amount of marginal sink patches and consequently, range contraction. We also demonstrate that the nature of the gradient is crucial for range elasticity. Gradients which do not select for lower dispersal at the margin than in the core (especially gradients in patch size, demographic stochasticity and extinction rate) do not lead to elastic range behavior. Thus, we predict that range contractions are likely to occur after periods of expansion for species living in gradients of increasing patch isolation, which suffer from Allee effects.
Jeanmichel Roberge - One of the best experts on this subject based on the ideXlab platform.
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edge creation and tree dieback influence the patch tracking metapopulation dynamics of a red listed epiphytic bryophyte
Journal of Applied Ecology, 2011Co-Authors: Jeanmichel Roberge, Stina Bengtsson, Soren Wulff, Tord SnällAbstract:1. Edges in landscapes have an effect on the abundance of many species but the underlying ecological mechanisms are poorly known for most taxonomic groups. One way to gain insight into the mechanisms is to examine how key demographic or metapopulation parameters are affected by proximity to edge. The main objective of this study was to investigate the effects of edge creation through clearcutting on the dynamics of forest species’ metapopulations. 2. We used the red-listed epiphytic moss Neckera pennata as a model species. Based on data from repeated surveys of a metapopulation and its host tree network in a hemiboreal forest, we tested the effect of edge creation on key metapopulation parameters: rates of local Colonization and extinction, local abundance growth and patch destruction through the fall of host trees. We predicted the long-term consequences of the edge effects using simulations with Bayesian statistical models. We also explored the potential effects of the pathogen Chalara fraxinea causing ash dieback, a tree disease currently spreading in Europe. 3. The Colonization Probability on host trees unoccupied by the moss increased with increasing connectivity to occupied trees. The growth of local populations on occupied trees decreased with increasing proximity to edge, and with initial local abundance. Stochastic extinctions of the epiphyte from standing trees were very rare and only occurred near the edge; most of the observed extinctions were deterministic due to tree fall. Tree fall decreased with increasing distance from the edge into the forest, and with increasing tree diameter. 4. Under edge conditions, simulations predicted decreases in the total number of host trees, number of occupied host trees, and in the total abundance of the epiphyte over a 30-year period. We suggest that ash dieback increases the tree fall rate and thereby the local extinction rate, leading to increased metapopulation extinction risk. 5. Synthesis and applications. The results show that small protected forest areas such as woodland key habitats may not allow long-term persistence of red-listed epiphytes if they are influenced by edge creation through clearcutting. Delineating uncut buffers of 50–100 m around the protected areas may alleviate such effects.
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Edge creation and tree dieback influence the patch‐tracking metapopulation dynamics of a red‐listed epiphytic bryophyte
Journal of Applied Ecology, 2011Co-Authors: Jeanmichel Roberge, Stina Bengtsson, Soren Wulff, Tord SnällAbstract:1. Edges in landscapes have an effect on the abundance of many species but the underlying ecological mechanisms are poorly known for most taxonomic groups. One way to gain insight into the mechanisms is to examine how key demographic or metapopulation parameters are affected by proximity to edge. The main objective of this study was to investigate the effects of edge creation through clearcutting on the dynamics of forest species’ metapopulations. 2. We used the red-listed epiphytic moss Neckera pennata as a model species. Based on data from repeated surveys of a metapopulation and its host tree network in a hemiboreal forest, we tested the effect of edge creation on key metapopulation parameters: rates of local Colonization and extinction, local abundance growth and patch destruction through the fall of host trees. We predicted the long-term consequences of the edge effects using simulations with Bayesian statistical models. We also explored the potential effects of the pathogen Chalara fraxinea causing ash dieback, a tree disease currently spreading in Europe. 3. The Colonization Probability on host trees unoccupied by the moss increased with increasing connectivity to occupied trees. The growth of local populations on occupied trees decreased with increasing proximity to edge, and with initial local abundance. Stochastic extinctions of the epiphyte from standing trees were very rare and only occurred near the edge; most of the observed extinctions were deterministic due to tree fall. Tree fall decreased with increasing distance from the edge into the forest, and with increasing tree diameter. 4. Under edge conditions, simulations predicted decreases in the total number of host trees, number of occupied host trees, and in the total abundance of the epiphyte over a 30-year period. We suggest that ash dieback increases the tree fall rate and thereby the local extinction rate, leading to increased metapopulation extinction risk. 5. Synthesis and applications. The results show that small protected forest areas such as woodland key habitats may not allow long-term persistence of red-listed epiphytes if they are influenced by edge creation through clearcutting. Delineating uncut buffers of 50–100 m around the protected areas may alleviate such effects.
K Van Looy - One of the best experts on this subject based on the ideXlab platform.
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integrated modelling of functional and structural connectivity of river corridors for european otter recovery
Ecological Modelling, 2014Co-Authors: K Van Looy, Jeremy Piffady, Cyril Cavillon, Philippe Landry, Thierry Tormos, Yves SouchonAbstract:Abstract Connectivity may be structural , based on adjacency of landscape features, or functional , based on how that adjacency translates to movement of organisms. We present a modelling approach that elucidates both aspects of connectivity to identify vital corridors and conservation priorities in a river network. For the dendritic network structure of river systems, at first a graph theoretic structure is developed to model the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchical modelling of species dispersal is applied to infer the influence of riparian corridor characteristics to the species Colonization. The integration of the functional and structural component is realized with a graph-theoretic connectivity measure. With this approach, the European otter Colonization of the Loire river basin over 25 years is modelled on the basis of large datasets on riparian corridor land use and hydromorphological characteristics of a 17,000 km river network. Channel straightening and riparian forest fragmentation are determined to be key elements to the functional connectivity. Road infrastructure is distinguished as a critical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Integration of the Bayesian model posterior Colonization Probability in the integrated connectivity analysis reveals the importance of the river network density to the otter Colonization and locates conservation priorities mainly in the lower parts of the river basin. Synthesis and applications Both functional and structural connectivity are essential elements in the contexts of ecological network identification for species conservation and recovery. We successfully developed an integrated modelling of both components of connectivity that highlighted the importance of the downstream basin for a well-connected ecological network for the otter.
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integrated modelling of functional and structural connectivity of river corridors for european otter recovery
Ecological Modelling, 2014Co-Authors: K Van Looy, Jeremy Piffady, Cyril Cavillon, Philippe Landry, Thierry Tormos, Yves SouchonAbstract:Abstract Connectivity may be structural , based on adjacency of landscape features, or functional , based on how that adjacency translates to movement of organisms. We present a modelling approach that elucidates both aspects of connectivity to identify vital corridors and conservation priorities in a river network. For the dendritic network structure of river systems, at first a graph theoretic structure is developed to model the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchical modelling of species dispersal is applied to infer the influence of riparian corridor characteristics to the species Colonization. The integration of the functional and structural component is realized with a graph-theoretic connectivity measure. With this approach, the European otter Colonization of the Loire river basin over 25 years is modelled on the basis of large datasets on riparian corridor land use and hydromorphological characteristics of a 17,000 km river network. Channel straightening and riparian forest fragmentation are determined to be key elements to the functional connectivity. Road infrastructure is distinguished as a critical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Integration of the Bayesian model posterior Colonization Probability in the integrated connectivity analysis reveals the importance of the river network density to the otter Colonization and locates conservation priorities mainly in the lower parts of the river basin. Synthesis and applications Both functional and structural connectivity are essential elements in the contexts of ecological network identification for species conservation and recovery. We successfully developed an integrated modelling of both components of connectivity that highlighted the importance of the downstream basin for a well-connected ecological network for the otter.