Document: STE-3-99-142

Effects of changes in land-use/land-cover and moisture levels on connectivity: Modeling characteristic habitat scales from the perspective of the organism.

WALTERS, S.*

University of Maryland, Frostburg, MD 21532 USA ¹

Abstract:
The goal of the research was to examine how the operational spatial scale of an organism interacts with the spatial scales at which disturbances (i.e., land use/land cover and climate change) occur in their impact on dispersal success. A spatially-explicit landscape model, incorporating land cover, topography, and general moisture level, was combined with an individual-based movement model to simulate dispersal of amphibian species to breeding pond habitats. The simulated landscapes were patterned after land cover and topographic gradients characteristic of the mid-Appalachian region. Behavior of the simulated species was parameterized after life history attributes of the red-spotted newt, Notophthalmus viridescens, and the green frog, Rana clamitans; characteristics that differed between the two included maximum dispersal distance and sensitivity to sub-optimal environmental conditions (frog newt for both traits). Successful dispersal from forest patches to new ponds was measured as a function of the grain size (fine- to coarse-grained) at which changes to the landscape - i.e., shifts to increasing agriculture and suburban development, and topographically dependent decreases in moisture levels across the landscape - occurred, as well as the traits of the dispersing organisms. Success of long-range dispersers was more strongly impacted by coarse-grained changes to the landscape than by finer levels of landscape change; short-range dispersers are more strongly impacted by the latter. The organism's level of sensitivity to sub-optimal habitat conditions interacted proportionately with the scale of landscape change in decreasing dispersal success. The non-linear relationships between scales of change in landscape characteristics, the species' traits, and dispersal success reveal the operational scales of the modeled organism: that is, they provide a measure of critical thresholds in effects of landscape pattern on the organism's behavior. Such understanding is crucial in predicting the effects of landscape change on persistence of populations of a given species.

Keywords: spatial scales

This abstract is being presented at: 10:45 AM in session:
Oral Session #38: Amphibian Ecology.