Domestic livestock and wild ungulate browsing can cause severe damage to forest regeneration. Aspen forests in particular have suffered extreme damage. Rocky mountain elk are considered the primary threat to the long-term survivability of aspen, because they impact aspen in so many ways. Elk have a height advantage over other ungulates and are able to reach higher in the crowns of saplings, often snapping the main bole and killing it. Elk rub antlers on small diameter trees (7 to 15 cm), creating wounds that allow entry for canker and wood decay fungi. Elk also gnaw or strip the bark (a.k.a. barking) of larger trees, allowing the entry of insects such as the bronze poplar borer.

References:  38, 91