Response of antelope bitterbrush to repeated prescribed burning in Central Oregon ponderosa pine forests

Abstract

Antelope  bitterbrush is a dominant shrub in many interior ponderosa pine forests  in the western United States. How it responds to prescribed fire is not  well understood, yet is of considerable concern to wildlife and fire  managers alike given its importance as a browse species and as a ladder  fuel in these fire-prone forests. We quantified bitterbrush cover,  density, and biomass in response to repeated burning in thinned  ponderosa pine forests. Low- to moderate-intensity spring burning  killed the majority of bitterbrush plants on replicate plots.  Moderately rapid recovery of bitterbrush density and cover resulted  from seedling recruitment plus limited basal sprouting. Repeated  burning after 11 years impeded the recovery of the bitterbrush  community. Post-fire seed germination following the repeated burns was  3-14-fold lower compared to the germination rate after the initial  burns, while basal sprouting remained fairly minor. After 15 years,  bitterbrush cover was 75-92% lower on repeated-burned compared to  unburned plots. Only where localized tree mortality resulted in an open  stand was bitterbrush recovery robust. By controlling bitterbrush  abundance, repeated burning eliminated the potential for wildfire  spread when simulated using a customized fire behavior model. The  results suggest that repeated burning is a successful method to reduce  the long-term fire risk imposed by bitterbrush as an understory ladder  fuel in thinned pine stands. Balancing the need to limit fire risk yet  provide adequate bitterbrush habitat for wildlife browse will likely  require a mosaic pattern of burning at the landscape scale or a burning  frequency well beyond 11 years to allow a bitterbrush seed crop to  develop.

Citation

Busse, Matt D.; Riegel, Gregg M. 2009. Response of antelope bitterbrush to repeated prescribed burning in Central Oregon ponderosa pine forests. Forest Ecology and Management. 257(3): 904-910.