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Journal Publications
Johnson, C.J., M.S. Boyce, R. Mulders,
A. Gunn, R.J. Gau, H.D. Cluff, and R.L. Case. 2004. Quantifying patch
distribution at multiple spatial scales: applications to wildlife-habitat
models. Landscape Ecology: in press.
Abstract
Multiscale analyses are widely employed for
wildlife-habitat studies. In most cases, however, each scale is considered
discrete and little emphasis is placed on incorporating or measuring the
responses of wildlife to resources across multiple scales. We modeled the
responses of three Arctic wildlife species to vegetative resources
distributed at two spatial scales: patches and collections of patches
aggregated across a regional area. We defined a patch as a single or
homogeneous collection of pixels representing 1 of 10 unique vegetation
types. We employed a spatial pattern technique, three-term local quadrat
variance, to quantify the distribution of patches at a larger regional
scale. We used the distance at which the variance for each of 10 vegetation
types peaked to define a moving window for calculating the density of
patches. When measures of vegetation patch and density were applied to
resource selection functions, the most parsimonious models for wolves and
grizzly bears included covariates recorded at both scales. Seasonal resource
selection by caribou was best described using a model consisting of only
regional scale covariates. Our results suggest that for some species and
environments simple patch-scale models may not capture the full range of
spatial variation in resources to which wildlife may respond. For mobile
animals that range across heterogeneous areas we recommend selection models
that integrate resources occurring at a number of spatial scales. Patch
density is a simple technique for representing such
higher-order spatial patterns. |
