Response of a rare endemic, Penstemon clutei, to burning and reduced belowground competition

Penstemon clutei, a rare perennial beard tongue endemic to the ponderosa pine forest of the Sunset Crater volcanic field of northern Arizona, presents an opportunity to test the hypothesis that restoration of historic ecosystem conditions may enhance the sustainability of a rare species. We tested prescribed burning and root trenching treatments as proxies for the surface fires and reduced tree densities characteristic of historic ponderosa pine ecosystems in a study area at OLeary Peak, part of the Sunset Crater volcanic field (Coconino National Forest, AZ). Prescribed burning killed many mature P. clutei plants and negatively affected density for at least 3 years post-burn. In contrast, trenching to cut root competition of overstory trees led to a 1200 percent increase in P. clutei plants. Precipitation influenced the response. Seed germination experiments showed that P. clutei does not have innate dormancy. Germination rates in the lab ranged from 5 to 70 percent under a range of environmental and fire-related conditions (i.e., cold stratification, light, exposure to ash, NH4), but these factors were not statistically significant. Tested seedling establishment rates in situ were very low (0.4(percent)). These experiments suggest that the observed P. clutei population increase following severe wildfires (1973 Burnt fire, 1996 Hochderffer fire) may have been due primarily to the removal of tree competition rather than to direct fire effects. Further experimentation is suggested to develop ecological information for thoughtful integration of ecosystem restoration with the habitat needs of rare plants