Determining Differences in the Spatial Distribution of Forest Structure on the Kaibab Plateau: Implications for forest management and the northern goshawk

Authors

Ryan S. Miller, USDA APHISFollow

Date of this Version

Spring 2001

Citation

Determining differences in the spatial distribution of forest structure on the Kaibab Plateau: Implications for forest management and the northern goshawk Ryan S. Miller. MS Thesis. Department of Forest Sciences, Colorado State University, 2001.

Abstract

The Kaibab Plateau, in North Central Arizona, has undergone extensive change in the last 100 years due to land management practices such as logging, road building, and fire suppression. The northern goshawk (Accipiter gentilis) has been a center of controversy, due to the potential effects of silvicultural practices on goshawk breeding habitat (Reynolds-1983, Bloom et al 1986, Kennedy 1989, Crocker-Bedford 1990). Current and past research efforts on the Kaibab Plateau have mapped Goshawk nesting territories and temporal change in nesting behavior and success. However, these research efforts have not determined how long-term spatial changes in land-use activities that have influenced forest structure, in tum affect goshawk nesting habitat. Researchers have proposed that differences in forest structure affect goshawk nesting success (Reynolds et al. 1992, Lang 1994), but no empirical evidence has been presented to support this proposition. Differences in forest structure on the North Kaibab Ranger District and the Grand Canyon National Park may affect goshawk use of each management area.

This study investigated possible forest structure differences between the North Kaibab Ranger District and the adjacent Grand Canyon National Park. Forest inventory data was collected for both the Grand Canyon National Park and North Kaibab Ranger District. Analysis was conducted at three scales biologically important to the northern goshawk: landscape, stand, and nest site.

Landscape analysis of the National Park and the National Forest found that there are significant differences in the size and spatial distribution of forest biomass between the two sites. Landscape metrics for the National Park and National Forest showed considerable differences with regard to forest cover type connectivity, size, shape, and distribution. The forests also demonstrated significant differences in tree-size class distributions, total basal area, and species composition. These differences were present at all three scales biologically important to the northern goshawk. The differences in spatial characteristics and composition of the forests could be the result of diverging management philosophies of the National Park and the National Forest. The effects of divergent management are not well understood and could have long lasting effects on the ecological integrity of the Kaibab Plateau and sensitive species such as the northern goshawk.