Evaluation of Burned Aspen Communities in Jackson Hole, Wyoming

Aspen has been declining in Jackson Hole for many years, a condition generally attributed to the fact that lightning fires have been aggressively suppressed since the early 1900s. It is also believed that burning will successfully regenerate aspen stands despite high elk numbers. To test this hypothesis, I evaluated 467 burned and 495 adjacent, unburned aspen stands at eight different locations within Jackson Hole. Aspen suckering was stimulated by burning, but most aspen stands still failed to produce new stems greater than 2 m tall where ungulate use was moderate or high. Only when elk use was low were burned aspen stands able to successfully regenerate. At those locations, however, unburned aspen stands also successfully regenerated. Evidence suggests that a combination of fire and continued elk use may eliminate many aspen clones. Introduction The relationship between vegetation and ungulates in Jackson Hole, Wyoming, has long been a subject of conflicting opinions and intense debate (Anderson 1958; Boyce 1989). Until the 1960s, it was thought that (1) Jackson Hole was not historic elk (Cervus elaphus) winter range; (2) European settlement forced elk to winter in the valley; and (3) supplemental feeding permitted the growth of an abnormally large elk herd; which (4) caused substantial damage to the winter range and a marked decline of aspen (Populus tremuloides) (Preble 1911; Murie 1951; Anderson 1958; Krebill 1972; Beetle 1974, 1979; Basile 1979; DeByle 1979; Weinstein 1979). However, federal and state biologists now believe that (1) large numbers of elk have wintered in Jackson Hole for the last several thousand years; (2) feedlots have only replaced winter range lost to human developments; (3) therefore, today’s elk population is not unnaturally high, although the distribution of wintering animals may have changed; (4) serious elk-induced range damage has not occurred (Cole 1969; Gruell 1979; Gruell 1980a,b; Boyce 1989); and (5) the elk herd would “naturally regulate” if sport hunting were terminated (Boyce 1989). Under this interpretation, aspen is thought to be a seral species maintained by fire, and human suppression of lightning fires is believed to be primarily responsible for the observed decline in aspen, not ungulate browsing (Loope and Gruell 1973; Gruell and Loope 1974). Gruell and Loope (1974:19–20) and Gruell (1980a:2) indicated that aspen stands burned in Jackson Hole were able to successfully regenerate, defined as producing new stems >2 m tall, despite heavy browsing—a claim similar to that made by the Park Service in Yellowstone (Kay 1990). According to Houston (1982:127), “data from [Yellowstone’s] northern range and adjacent areas showed that aspen often reproduced successfully when burned in the presence of ungulate populations.” While Despain et al. (1986:107) stated that “data from some locations on the northern range have proven that aspen, when