Aspen in the Sierra Nevada: Regional Conservation of a Continental Species

Quaking aspen (Populus tremuloides Michx.), a common species in North America, is a minor species in the Sierra Nevada of California. However, the limited coverage of aspen in this area appears to carry a disproportionate biodiversity load: numerous species are dependent on the unique components of aspen forests for habitat. Land managers in the region believe the species is declining due to fire suppression policies of the past century. Recent research from other regions shows mixed results when assessing the extent of decline. This review focuses on the crossroads between human and natural history to describe a broader picture of aspen ecology in the Sierra Nevada. The method used here combines a review of the ecological literature with historical synthesis. A central conclusion is that the current “decline” in aspen must be placed in the context of an unusual regeneration pulse brought on by intensive Euro-American resource extraction activities of the late 19th century. We address unique features of the Sierra aspen population, the interface of climate change and human-caused disturbance, and conservation strategies for restoration of an aspen community more closely aligned with contemporary climate-disturbance cycles. Conservation recommendations include reintroduction of mixed-severity natural fires and complimentary wildlife, such as top predators, where practical, plus allowance for local flexibility where deviations are appropriate based on ecology and social concerns.