Aspen decline, aspen chemistry, and elk herbivory: are they linked

A spen (Populus tremuloides) provides important habitat for mammals and birds1–3, improves water retention in watersheds,4 and has high aesthetic appeal in autumn. However, the amount and quality of aspen cover in the West has been declining for many years. For example, aspen cover in the Dixie and Fishlake National forests in Utah has decreased by more than 60 % from historic levels, and in the Uinta National Forest aspen cover has been reduced by nearly 40%5. The decline is so severe that Mueggler4 suggested that aspen-dominated woodlands might shift to shrub– grasslands under current management practices. The decline is disturbing because in the western United States, aspens are second only to riparian areas in terms of biodiversity.1 Why is aspen declining in the West? Climate change, reduced fi re intervals, and browsing by deer, elk, and cattle1,3,5,6 all have been suggested as contributing to the dec line of aspen. Aspen is a highly palatable browse fo