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Conclusions: In fragmented watersheds, macrohabitat attributes measured at the patch scale were far more effective in predicting trout translocation success than measurements taken at the landscape scale Thresholds/Learnings: As a course filter indicator of cutthroat trout translocation success, the study found that translocations have a greater than 50% chance of fruitful establishment in watersheds >14.7km2 in area. Synopsis: This study aimed to identify stream-scale and basin-scale macrohabitat attributes limiting successful translocation and persistence of native cutthroat trout populations in fragmented landscapes along the Rio Grande. The study developed models of habitat attributes measured at two scales...
[Excerpt from Introduction] "The San Francisco Bay Estuary supports a large and diverse bird community. More than 50% of most Pacific flyway diving duck populations are found in the Estuary during the winter months (Trost 2002; U.S. Fish and Wildlife Service 2002). San Francisco Bay has been designated as a site of international importance for shorebirds (Western Hemisphere Shorebird Reserve Network), supporting millions of individuals (Morrison et al. 2001; Takekawa et al. 2001; Warnock et al. 2002), including species that use tidal marsh habitats. In total, the Bay’s tidal marshes support at least 113 bird species that represent 31 families (Takekawa et al., in press)..."
The rapid expansion of road networks has reduced connectivity among populations of flora and fauna. The resulting isolation is assumed to increase population extinction rates, in part because of the loss of genetic diversity. However, there are few cases where loss of genetic diversity has been linked directly to roads or other barriers. We analysed the effects of such barriers on connectivity and genetic diversity of 27 populations of Ovis canadensis nelsoni (desert bighorn sheep). We used partial Mantel tests, multiple linear regression and coalescent simulations to infer changes in gene flow and diversity of nuclear and mitochondrial DNA markers. Our findings link a rapid reduction in genetic diversity (up to...
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Conclusions: Report identifies regional patterns of habitat disturbance, land use practices, and population trends relative to greater sage-grouse. In general, the most important landscape characteristics influencing sage-grouse populations are the proximity of leks (areas in which males perform to nesting habitat for and The report examined findings from studies that indicate several area and distance specific conservation thresholds for maintaining viable sage-grouse habitat. Thresholds/Learnings: Male sage-grouse prefer sod-forming grasses or bare ground for leks; female sage-grouse prefer dense sagebrush stands surrounding leks for nesting; gentle terrain characterized by <10% slope; <5% of existing sagebrush...
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Conclusions: Emigration rates are closely tied to edge structure. Low contrast edges promote edge permeability Thresholds/Learnings: Synopsis: The behavior of two butterfly species, one habitat specialist and one habitat generalist, were tracked at four prairie edges to determine the extent to which edge structure affects emigration. The specialist species responded strongly to all edges, and was particularly affected by edge density. The generalist species responded strongly only to high contrast edges. Emigration rates are closely tied to edge structure. Therefore, promoting low contrast edges in conservation planning may positively influence edge permeability and species richness in highly fragmented landscapes.
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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...
Landscape-level variables operating at multiple spatial scales likely influence wetland amphibian assemblages but have not been investigated in detail. We examined the significance of habitat loss and fragmentation, as well as selected within-wetland conditions, affecting amphibian assemblages in twentyone glacial marshes. Wetlands were located within ttrban and agricultural regions of central and southwestern Minnesota, USA and were distributed across two ccoregions: tallgrass prairie and northern hardwood forest. We surveyed amphibian assemblages and used a geographic information system to quantify land-use variables at lhree scales: 500, 1000, and 2500 m. Ten species of amphibians were detected, the most abundant...
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Conclusions: Marten capture rates were negatively correlated with increasing proximity of open areas and increasing extent of high-contrast edges. Forested landscapes were unsuitable for martens when the average nearest-neighbor distance between open, non-forested patches was <100m. Thresholds/Learnings: Synopsis: This study aimed to determine whether American marten abundance changed with incremental increases in habitat fragmentation caused by the combined effects of natural openings and timber clearcuts. Researchers evaluated differences in marten capture rates in 18 study sites with different levels of fragmentation. Martens appeared to respond negatively to low levels of habitat fragmentation, even with remaining...
    map background search result map search result map The influence of forest fragmentation and landscape pattern on American martens. Butterfly responses to habitat edges in highly fragmented prairies of central Iowa. Minimum habitat requirements for establishing translocated cutthroat trout populations. Critical thresholds in species responses to landscape structure. Conservation Assessment of Greater Sage-Grouse and Sagebrush Habitats The influence of forest fragmentation and landscape pattern on American martens. Minimum habitat requirements for establishing translocated cutthroat trout populations. Butterfly responses to habitat edges in highly fragmented prairies of central Iowa. Critical thresholds in species responses to landscape structure. Conservation Assessment of Greater Sage-Grouse and Sagebrush Habitats