Populations in fragmented landscapes experience reduced gene flow, lose genetic diversity over time and ultimately face greater extinction risk. Improving connectivity in fragmented landscapes is now a major focus of conservation biology. Designing effective wildlife corridors for this purpose, however, requires an accurate understanding of how landscapes shape gene flow. The preponderance of landscape resistance models generated to date, however, is subjectively parameterized based on expert opinion or proxy measures of gene flow. While the relatively few studies that use genetic data are more rigorous, frameworks they employ frequently yield models only weakly related to the observed patterns of genetic isolation. Here, we describe a new framework that uses expert opinion as a starting point. By systematically varying each model parameter, we sought to either validate the assumptions of expert opinion, or identify a peak of support for a new model more highly related to genetic isolation. This approach also accounts for interactions between variables, allows for nonlinear responses and excludes variables that reduce model performance. We demonstrate its utility on a population of mountain goats inhabiting a fragmented landscape in the Cascade Range, Washington.

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The Pacific Northwest of the United States is currently embroiled in an acrimonious debate over the management of federal forest lands. Constructive resolution of this debate will require better information on a broad range of forest management issues. This study focuses on one such issue: the development of landscape pattern in response to alternative forest cutting plans and the degree to which established landscape patterns can be changed. Dispersed cutting has been conducted on federal lands in the western United States for > 40 yr, but alternative cutting plans are now being considered. To assess the effects of different disturbance processes on the development of landscape pattern, we compare dispersed— and aggregated—cutting plans using a simple, rule—based simulation model that incorporates realistic regulatory and logistic constraints. Our results indicate that, once established, the landscape pattern created by dispersed disturbances is difficult to erase without a substantial reduction in the disturbance rate or a reduction in the minimum stand age eligible for disturbance. Change in landscape pattern can lag substantially behind change in the rules governing pattern generation.

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A landscape plan based on historical fire regimes for a managed forest ecosystem: the Augusta Creek study. Gen. Tech.

We used bivariate scaling and logistic regression to investigate multiple-scale habitat selection by American marten (Martes americana). Bivariate scaling reveals dramatic differences in the apparent nature and strength of relationships between marten occupancy and a number of habitat variables across a range of spatial scales. These differences include reversals in the direction of an observed association from positive to negative and frequent dramatic changes in the apparent importance of a habitat variable as a predictor of marten occurrence. Logistic regression on the optimally scaled input variables suggests that at the scale of home ranges, marten select landscapes with high average canopy closure and low fragmentation. Within these low fragmented landscapes, marten select foraging habitat at a fine scale within late-seral, middle-elevation mesic forests. In northern Idaho, optimum American marten habitat, therefore, consists of landscapes with low road density, low density of non-forest patches with high canopy closure, and large areas of middle-elevation, late successional mesic forest. Comparison of current landscape conditions to those expected under the historic range of variability indicates that road building and timber harvest in the past century may have substantially reduced the amount of suitable marten habitat in northern Idaho. Our results are generally consistent with previous research in the Rocky Mountains, with additional insights related to the relative importance, functional form, and scale at which each habitat variable has the largest influence on marten occurrence.

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