PARENT SESSION
Oral Session #30: Landscape Ecology: Dynamics and patterns. Presiding: A. Hansen.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Madison Ballroom D.
Historic range of variability in landscape structure for the Greater Yellowstone Ecosystem.
Tinker, Daniel1, Romme, William2, Despain, Don3, 1 2 3
ABSTRACT- Evaluating the effects of intensive timber harvesting on landscape structure in Rocky Mountain coniferous forests requires an estimate of the historic range of variability (HRV) for these landscapes. Arc/Info and FRAGSTATS were used to calculate landscape metrics on two ~130,000-ha landscapes in the Greater Yellowstone Ecosystem (GYE): 1) Yellowstone National Park (YNP), shaped by natural fires; and 2) the adjacent Targhee National Forest (TNF), which has undergone intensive clearcutting for three decades. Landscape metrics were calculated at 20-yr intervals for YNP, from 1705-1995. The metrics were used to evaluate the effects of small vs. large fires on landscape structure, and were then compared to similar metrics for pre- and post-harvest landscapes of the TNF. Total number of patches in YNP was higher after the large fires of 1988 than at any other time during the 290-yr study period. Mean patch size, core area per patch, and the amount of unburned forest was reduced after 1988, while the number of unburned patches increased six-fold. In the TNF, the number of patches increased threefold following timber harvesting, and mean patch size was reduced almost 70%. All of the post-harvest TNF landscape metrics fell outside the HRV for YNP, yet the pre-harvest TNF landscape was within the HRV for YNP. Estimating the HRV in landscape structure for YNP may provide reference conditions by which to evaluate current management practices on adjacent public lands.
KEY WORDS: historic range of variability, landscape structure, landscape metrics, Yellowstone National Park