Long-term Responses of Penstemon clutei (Sunset Crater Beardtongue) to Root Trenching and Prescribed Fire: Clues for Population Persistence

Sunset Crater Beardtongue
Photo: Jake Bacon, Arizona Daily Sun.

Penstemon clutei A. Nelson (Sunset Crater beardtongue) is narrowly endemic to the cinder hills and volcanic fields northeast of Flagstaff, Arizona. Disturbances such as wildfire, tornadoes, logging activity, and tree mortality from bark beetle outbreaks appear to stimulate regeneration of this species, but the manner in which populations persist between events is still largely unknown. 
From 1994-2000, we examined P. clutei responses to prescribed burning and root trenching treatments that were experimentally implemented as proxies for surface fire and reduced tree densities that might be observed following natural disturbance. We revisited this experiment in 2008 to assess long-term effects of the treatments. We also collected soil samples at this time to evaluate the importance of a persistent seed bank in population dynamics. 
Results from this work suggest that disturbances that reduce competition for soil resources may be associated with long-term population persistence. Latent seed banks appear to be of only minor importance in recovery after disturbance; however, additional research with larger sample sizes would allow for greater confidence in this conclusion. We also recommend that additional long-term research be conducted on the response of this species to specific disturbances and stressors such as wildfire, tree mortality from bark beetle outbreaks, and water limitations.
Read the article in Calochortiana