Conditions and Recommendations for Quaking Aspen at Bryce Canyon National Park

Rogers, Paul; Vasquez, Eric

doi:10.36967/2319290

In cooperation with Bryce Canyon National Park, we undertook a survey of quaking aspen (Populus tremuloides Michx.) conditions throughout the park with the intention of better understanding conditions and prescribing corrective measures where needed. There are clear disparities within the park between sustainable aspen conditions and failing stands. Based on condition of mature trees, but most importantly regeneration and recruitment of juvenile stems, most aspen forests within Bryce Canyon are in poor condition. Aspen recruitment—generally sapling-sized trees that have survived browsing ungulates—is the most important metric of future stand resilience and here we found 83% of all aspen sample locations were below sustainable levels. Over half our aspen sample stands had no recruitment at all. The prime cause of this park-wide depletion of aspen recruitment is herbivory by elk, mule deer, and domestic cattle. A bright spot in this survey was the complete opposite condition—healthy overstory, abundant recruitment, and sustainable browse levels—in two large areas where fires have burned in recent years. These fires have also contributed to an expansion, in comparison to a 20-year-old vegetation map, in total aspen area within the park. In other words, while aspen overall have increased in area, those expansions are concentrated, and the broader range of aspen communities are declining. As a final note, Bryce Canyon National Park has seen a recent infestation, though limited in scope, of the invasive oystershell scale (Lepidosaphes ulmi L.) insect in the area around Iron Spring. Continued monitoring and, in some cases, aggressive action will be required to mitigate potentially severe effects of this insect on future aspen communities.

Conditions and Recommendations for Quaking Aspen at Bryce Canyon National Park

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