Bulkley Valley Research Centre - Science in the Public Interest

Aspen ecology and management in the US Southwest

Wednesday December 4, 2019  12:00pm-1:00pm

The Old Church - Smithers, BC

About this presentation

Quaking aspen (Populous tremuloides) is an iconic species with a range extending across much of North America. In the US Southwest, near the southern end of the species range, sustaining aspen populations has been a challenge for decades. Ungulate browse is a major limiting factor for regeneration success while biotic damaging agents play a role in overstory decline. I will talk about strategies for successful aspen management in the US Southwest, threats to those strategies, and current research and monitoring efforts.


Quaking aspen (Populus tremuloides) is in decline across much of the western United States, and this decline is especially pronounced on the southwestern edge of the tree’s range, which includes Arizona. This is concerning because, as one of the few hardwood species present on the landscape, aspen provides critical biodiversity in addition to other ecosystem services such as watershed management, carbon sequestration, hunting revenue, and aesthetic and recreational value. A number of factors likely contribute to this decline including drought, ungulate browse, fire suppression, insects, and disease. Of particular concern in Arizona is the emerging invasive insect, oystershell scale (OSS; Lepidosaphes ulmi). Fenced exclosures have been a successful management strategy to promote aspen regeneration, but the long-term success of exclosures is uncertain, as OSS is presently impacting aspen stands within exclosures. No research has been conducted on how management activities could reduce OSS infestation, which may be critical knowledge for promoting long-term sustainability of aspen in Arizona. This talk will focus on general aspen ecology and management in Arizona and New Mexico, as outlined above, in addition to covering a new silviculture-based research project related to OSS management.

About Dr. Kristen Waring 

Dr. Kristen Waring is Professor of Silviculture and Applied Forest Health in the School of Forestry, Northern Arizona University, where she has worked since 2006. She has forestry degrees from the University of Montana and the University of California-Berkeley and specializes in finding solutions to a wide assortment of challenging forest health problems. She is currently a Carlos Rico Fulbright Scholar for North American Studies and visiting scholar at UNBC working with Che Elkin on silviculture and climate change adaptation. She will continue work on this topic while based in Durango, Mexico in spring 2020.

Importance to Northwest BC

Aspen ecology and management are of utmost importance to maintaining biodiversity and other important ecological values in the western US. However, aspen is not expected to perform well in the future climate, particularly on the southern edges of it range. Climate envelop models project expansion in Canada, and it is important to understand issues facing aspen elsewhere. Such understanding could lead to improved management strategies and a greater appreciation for the species.

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