Category: Ecological Research
Title: Long-term Responses of Penstemon clutei (Sunset Crater Beardtongue) to Root Trenching and Prescribed Fire: Clues for Population Persistence
Author: * Springer, J.D., * Fule, P.Z., * Huffman, D.W.
Subject: Penstemon, Vegetation studies
Abstract: 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. In 2008, the mean number of P. clutei plants on trenched plots had declined with time, but was still significantly higher than on the control plots (mean density of 7.4 plants in trenched plots vs. 0.6 plants in control plots). There was no significant difference in density between burned and unburned plots. Only 21 P. clutei seedlings emerged from 176 soil seed bank samples, and we found no correlation between the number of P. clutei plants aboveground and the number of emergents from the samples. A targeted study to obtain samples near the base of reproductively mature plants produced 9 emergents from 30 samples. 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.
Publisher: Utah Native Plant Society