The Experts below are selected from a list of 4404 Experts worldwide ranked by ideXlab platform
Andrew M. Liebhold - One of the best experts on this subject based on the ideXlab platform.
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tree diversity regulates Forest Pest invasion
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Kevin M Potter, Andrew M. LiebholdAbstract:Nonnative Pests often cause cascading ecological impacts, leading to detrimental socioeconomic consequences; however, how plant diversity may influence insect and disease invasions remains unclear. High species diversity in host communities may promote Pest invasions by providing more niches (i.e., facilitation), but it can also diminish invasion success because low host dominance may make it more difficult for Pests to establish (i.e., dilution). Most studies to date have focused on small-scale, experimental, or individual Pest/disease species, while large-scale empirical studies, especially in natural ecosystems, are extremely rare. Using subcontinental-level data, we examined the role of tree diversity on Pest invasion across the conterminous United States and found that the tree-Pest diversity relationships are hump-shaped. Pest diversity increases with tree diversity at low tree diversity (because of facilitation or amplification) and is reduced at higher tree diversity (as a result of dilution). Thus, tree diversity likely regulates Forest Pest invasion through both facilitation and dilution that operate simultaneously, but their relative strengths vary with overall diversity. Our findings suggest the role of native species diversity in regulating nonnative Pest invasions.
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a highly aggregated geographical distribution of Forest Pest invasions in the usa
Diversity and Distributions, 2013Co-Authors: Andrew M. Liebhold, Deborah G Mccullough, Laura M Blackburn, Susan J Frankel, Betsy Von Holle, Juliann E AukemaAbstract:Aim Geographical variation in numbers of established non-native species provides clues to the underlying processes driving biological invasions. Specifically, this variation reflects landscape characteristics that drive non-native species arrival, establishment and spread. Here, we investigate spatial variation in damaging non-native Forest insect and pathogen species to draw inferences about the dominant processes influencing their arrival, establishment and spread. Location The continental USA, including Alaska (Hawaii not included). Methods We assembled the current geographical ranges (county-level) of 79 species of damaging non-indigenous Forest insect and pathogen species currently established in the continental USA. We explored statistical associations of numbers of species per county with habitat characteristics associated with propagule pressure and with variables reflecting habitat invasibility. We also analysed relationships between the geographical area occupied by each Pest species and the time since introduction and habitat characteristics. Results The geographical pattern of non-native Forest Pest species richness is highly focused, with vastly more species in the north-eastern USA. Geographical variation in species richness is associated with habitat factors related to both propagule pressure and invasibility. Ranges of the non-native species are related to historical spread; range areas are strongly correlated with time since establishment. The average (all species) radial rate of range expansion is 5.2 km yr 1 , and surprisingly, this rate did not differ among foliage feeders, sap-feeders, wood borers and plant pathogens. Main conclusions Forest Pest species are much more concentrated in the north-eastern region of the USA compared with other parts of the country. This pattern most likely reflects the combined effects of propagule pressure (Pest arrival), habitat invasibility (Pest establishment) and invasion spread. The similarity in historical spread among different types of organisms indicates the importance of anthropogenic movement in spread.
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Forest Pest management in a changing world
International Journal of Pest Management, 2012Co-Authors: Andrew M. LiebholdAbstract:The scope, context and science guiding Forest Pest management have evolved and are likely to continue changing into the future. Here, I present six areas of advice to guide practitioners in the implementation of Forest Pest management. First, human dimensions will continue to play a key role in most Pest problems and should always be a primary consideration in management. Next, managers must recognize that it is practically impossible to use population suppression to prevent outbreaks that extend over large geographic regions. Silvicultural practices can sometimes be effective at reducing Forest susceptibility to outbreaks but these methods should be based on sound science. Many of the most damaging Forest Pests are non-native species and minimizing the invasion problem is most effective when steps are taken early on in the invasion process. Furthermore, classical biological control and selection for host resistance are important approaches to managing established non-native Pest species. Finally, plantat...
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dispersal polymorphism in an invasive Forest Pest affects its ability to establish
Ecological Applications, 2009Co-Authors: Christelle Robinet, Andrew M. LiebholdAbstract:Given the increasing number of biological invasions, there is a crucial need to identify life history traits that promote invasion. Invasiveness reflects capabilities for both establishment after introduction and spread following establishment. In this paper, we explore, via simulation, the interacting effects of dispersal and Allee effects on both invasion processes. Dispersal capability is a trait that has been widely recognized to facilitate invasions. However, dispersal dilutes local population densities in isolated populations and this could strengthen Allee effects, ultimately promoting extinction of invading populations. A spatially explicit, stochastic individual-based model was used to simulate dispersal, mating, and growth in isolated, newly arrived invading populations. We used the invasion of North America by the gypsy moth, Lymantria dispar, as a case study because: (1) a great amount of biological data on the species is available; (2) Allee effects caused by mate location failure are known to play an important role in its establishment and spread; and (3) a dispersal polymorphism has previously been identified (i.e., in some populations adult females are fully capable of flight, but in other populations females are not able to fly). We considered the introduction of a hypothetical number of eggs at a single location, originating from populations with varying female dispersal capabilities, and we then used simulation models to evaluate the population growth rate over two generations as well as spread distance. Nondispersing populations had the highest growth rates and inclusion of even limited dispersal capabilities caused population growth rates to be greatly diminished. The Allee threshold was 700 eggs for nondispersing populations and 1400 eggs for the long-distance dispersing populations. Thus, for an intermediate number of eggs initially introduced, nondispersing populations would most likely establish, whereas dispersing populations would likely become extinct. Spread distance increased linearly with the number of eggs initially introduced in both dispersing and nondispersing populations but rapidly reached a limit for nondispersing populations. Though species capable of long-distance dispersal may invade a larger area than nondispersing species, their growth rates are likely to be considerably lower, and eradication should be easier. Following these results, strategies for managing invasions should be adjusted for the interactions between Allee effects and dispersal.
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Proceedings: Spatial analysis and Forest Pest management
1993Co-Authors: Andrew M. Liebhold, Hope R. BarrettAbstract:Twenty papers on the application of spatial analysis to Forest insect and disease problems presented at a workshop on spatial analysis and Forest Pest management.
Kyrre L Kausrud - One of the best experts on this subject based on the ideXlab platform.
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population dynamics in changing environments the case of an eruptive Forest Pest species
Biological Reviews, 2012Co-Authors: Kyrre L Kausrud, Bjorn Okland, Olav Skarpaas, Jeanclaude Gregoire, Nadir Erbilgin, Nils Chr StensethAbstract:In recent decades we have seen rapid and co-occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major Forest Pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi-annual landscape-wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co-occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed-species and age-heterogeneous Forests with good site-matching tend to be less susceptible to large-scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating Forestry practices should be adopted as soon as possible considering the time lags involved.
Nils Chr Stenseth - One of the best experts on this subject based on the ideXlab platform.
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population dynamics in changing environments the case of an eruptive Forest Pest species
Biological Reviews, 2012Co-Authors: Kyrre L Kausrud, Bjorn Okland, Olav Skarpaas, Jeanclaude Gregoire, Nadir Erbilgin, Nils Chr StensethAbstract:In recent decades we have seen rapid and co-occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major Forest Pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi-annual landscape-wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co-occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed-species and age-heterogeneous Forests with good site-matching tend to be less susceptible to large-scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating Forestry practices should be adopted as soon as possible considering the time lags involved.
Bjorn Okland - One of the best experts on this subject based on the ideXlab platform.
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population dynamics in changing environments the case of an eruptive Forest Pest species
Biological Reviews, 2012Co-Authors: Kyrre L Kausrud, Bjorn Okland, Olav Skarpaas, Jeanclaude Gregoire, Nadir Erbilgin, Nils Chr StensethAbstract:In recent decades we have seen rapid and co-occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major Forest Pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi-annual landscape-wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co-occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed-species and age-heterogeneous Forests with good site-matching tend to be less susceptible to large-scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating Forestry practices should be adopted as soon as possible considering the time lags involved.
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timber import and the risk of Forest Pest introductions
Journal of Applied Ecology, 2009Co-Authors: Olav Skarpaas, Bjorn OklandAbstract:Summary 1 Many invasive species are introduced by trade, and there is a need for studies of pre-emptive measures to lower the risk of introductions, as post-establishment management is often extremely costly or nearly impossible. 2 In this study, we present a generic model for the first step of the invasion process for trade-imported Pests, and further develop this model for potentially harmful bark beetles to assess the risk of introductions and alternative management options. 3 Our results suggest that introductions of bark beetles are likely, given present timber import practices, and that immigration may often go undetected by pheromone traps. 4 The most effective measures for reducing introduction risk were those aimed at isolating the storage from Forest (storage enclosure, location) followed by those reducing the available resources for Forest Pests (debarking, timber irrigation, rapid processing), whereas delayed import was least effective. 5 Synthesis and applications: The generic model framework of species introductions presented here may easily be adapted to other import systems. The submodels of population dynamics and dispersal are also quite general, and we expect our qualitative results to hold in many cases, although the models were parameterized for bark beetles in this study. Our results suggest that detection of dispersal from storage to Forests will be difficult, which implies that management actions should not be deferred until after detection in nature, as the Pest species may then already be established and eradication may be too late. However, pre-emptive measures reducing propagule pressure at one or several stages of the introduction process, in particular isolation measures, may strongly reduce introduction risk.
Olav Skarpaas - One of the best experts on this subject based on the ideXlab platform.
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population dynamics in changing environments the case of an eruptive Forest Pest species
Biological Reviews, 2012Co-Authors: Kyrre L Kausrud, Bjorn Okland, Olav Skarpaas, Jeanclaude Gregoire, Nadir Erbilgin, Nils Chr StensethAbstract:In recent decades we have seen rapid and co-occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major Forest Pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi-annual landscape-wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co-occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed-species and age-heterogeneous Forests with good site-matching tend to be less susceptible to large-scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating Forestry practices should be adopted as soon as possible considering the time lags involved.
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timber import and the risk of Forest Pest introductions
Journal of Applied Ecology, 2009Co-Authors: Olav Skarpaas, Bjorn OklandAbstract:Summary 1 Many invasive species are introduced by trade, and there is a need for studies of pre-emptive measures to lower the risk of introductions, as post-establishment management is often extremely costly or nearly impossible. 2 In this study, we present a generic model for the first step of the invasion process for trade-imported Pests, and further develop this model for potentially harmful bark beetles to assess the risk of introductions and alternative management options. 3 Our results suggest that introductions of bark beetles are likely, given present timber import practices, and that immigration may often go undetected by pheromone traps. 4 The most effective measures for reducing introduction risk were those aimed at isolating the storage from Forest (storage enclosure, location) followed by those reducing the available resources for Forest Pests (debarking, timber irrigation, rapid processing), whereas delayed import was least effective. 5 Synthesis and applications: The generic model framework of species introductions presented here may easily be adapted to other import systems. The submodels of population dynamics and dispersal are also quite general, and we expect our qualitative results to hold in many cases, although the models were parameterized for bark beetles in this study. Our results suggest that detection of dispersal from storage to Forests will be difficult, which implies that management actions should not be deferred until after detection in nature, as the Pest species may then already be established and eradication may be too late. However, pre-emptive measures reducing propagule pressure at one or several stages of the introduction process, in particular isolation measures, may strongly reduce introduction risk.