Disturbance and Stand Development of a Colorado Subalpine Forest

Abstract

Stand development patterns were examined in an Engelmann spruce (Picea engelmannii), subalpine fir (Abies lasiocarpa) and lodgepole pine (Pinus contorta var. latifolia) forest in Rocky Mountain National Park in northern Colorado. Two old-growth stands (with fine-scale windthrows dominating dynamics) and a 260-yr-old post-fire stand were sampled for tree ages, sizes, growth, and replacement patterns in windthrow gaps. Visual assessment of frequency of growth releases in increment cores, and dendrochronology, were used. The post-fire stand was initially colonized by spruce and pine but fir has become increasingly abundant in the past 100 yr; canopy dominance is shifting from pine towards spruce and fir. In old growth stands, fir is the more common gap occupant but has a greater rate of treefall and spruce has greater longevity implying that both will continue to codominate the stand. It is concluded that there are substantial differences in response to fire, but disturbance by wind does not differentially favour spruce or fir