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Conclusions: The study recorded flushing responses (whether or not an animal fled in response to disturbance) and flush distances of 6 species of diurnal raptors exposed to walking and vehicle disturbances in order to calculate minimum distances for species-specific buffer zones. In general, walking disturbances resulted in more flushing than vehicle disturbances for all species except the prairie falcon. For walking disturbances, a linear relationship existed between flight distance and body mass, with lighter species flushing at shorter distances; however, this trend did not hold for vehicle disturbance. Birds flushed at much shorter distances in response to approaching vehicles. Thresholds/Learnings: Buffer...
Conclusions: Assessments of metapopulation structure must consider landscape pattern, but also the non-linear responses of organisms to such patterns Thresholds/Learnings: Synopsis: This study used beetles to empirically test the reliability of neutral percolation models to predict critical thresholds of landscape connectivity. Beetle movements declined sharply when grass cover dropped below 20% of the experimental plot. The findings of this study differed from what was predicted by the model, indicating that landscape connectivity is not dependent on spatial pattern alone, but is also highly dependent how individual organisms move within and among patches depending on the amount of cover. The results suggest that...
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Conclusions: The nature of the surrounding matrix contributes significantly to the degree of patch isolation; matrix modification may improve habitat connectivity and genetic distribution in fragmented landscapes. Thresholds/Learnings: Synopsis: This study challenges traditional assumptions about the uniform nature of the matrix, and the reliance on distance alone as an indicator of patch isolation, by testing whether the type of inter-patch matrix contributes significantly to patch isolation in butterfly populations. The author tracked the movement of six butterfly species between patches of meadow habitat through two natural matrix types (conifer forest and willow thicket). All taxa of butterflies studied responded...
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Conclusions: Reduction in landscape carrying capacity for wolf population distribution and viability depends largely on the degree of road density, public land ownership, amount of forest cover and high elk densities (another indicator of suitable habitat). Synopsis: This study employed two types of spatial models to evaluate the potential of wolf reintroduction in the southern Rocky Mountain region. A multiple logistic regression was used to develop a resource-selection function relating wolf distribution in the Greater Yellowstone region with regional-scale habitat variables. Researchers also used a spatially explicit population model to predict wolf distribution and viability at several potential reintroduction...
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Synopsis: A simulation model, modified from percolation theory, was empirically tested to determine if population distribution patterns correlated with different landscape patterns, for different species across a landscape. Using two grasshopper species in a short-grass prairie of north-central Colorado, the experiment found that the threshold for population aggregation (random to clumped distribution) was differentially affected by dispersal ranges and habitat specialization for habitat generalists and habitat specialists, respectively. Habitat generalists aggregated differentially depending on dispersal abilities. Generalist species with good dispersal abilities aggregated when <35% of the landscape consisted...
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Synopsis: Because recent bark beetle population eruptions have exceeded the frequencies, impacts, and ranges documented during the previous 125 years, researchers have been prompted to determine what factors trigger broad scale outbreaks, and how do these factors interact? How do human activities, such as forest management, alter these interactions, and thus the frequency, extent, severity, and synchrony of outbreaks? Extensive host tree abundance and susceptibility, concentrated beetle density, favorable weather, optimal symbiotic associations, and escape from natural enemies must occur jointly for beetles to surpass a series of thresholds and exert widespread disturbance. Eruptions occur when key thresholds are...
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Synopsis: This study investigated the magnitude of change in landscape structure resulting from road and logging since the onset of timber harvesting in 1950. Overall, roads were found to have had a greater impact on landscape structure than logging. A three-fold increase in road density between 1950 and 1993 accounted for most of the changes in landscape configuration including mean patch size, edge density, and core area. Change in landscape structure varied as a function of landscape extent. At a large scale of 228,000 ha, change in landscape change over time was trivial, suggesting that the landscape is capable of incorporating disturbances with minimal impact. At intermediate scales of 1000-10,000 ha, change...
    map background search result map search result map The matrix matters: effective isolation in fragmented landscapes. Critical thresholds in species responses to landscape structure. Impacts of landscape change on wolf restoration success: planning a reintroduction program based on static and dynamic spatial models. Cross-scale drivers of natural disturbances prone to anthropogenic amplification: the dynamics of bark beetle eruptions Comparative evaluation of experimental approaches to the study of habitat fragmentation effects Response of wintering grassland raptors to human disturbance. The matrix matters: effective isolation in fragmented landscapes. Response of wintering grassland raptors to human disturbance. Critical thresholds in species responses to landscape structure. Comparative evaluation of experimental approaches to the study of habitat fragmentation effects Impacts of landscape change on wolf restoration success: planning a reintroduction program based on static and dynamic spatial models. Cross-scale drivers of natural disturbances prone to anthropogenic amplification: the dynamics of bark beetle eruptions