Monday, 17 November 2003: 1:30 PM
Positive effects of prescribed fire on understory vegetation in mixed-conifer forests of the southern Sierra Nevada, CA (USA)
Sequoia and Kings Canyon National Parks began a prescribed fire program in 1969 to restore conditions altered by many decades of fire exclusion. A monitoring program was initiated in 1982 to determine whether management objectives were met and to document unexpected changes following prescribed fire. Much of the parks’ prescribed fire activity has occurred in the giant sequoia-mixed conifer forest located between 1650-2200 meters in elevation, as well as in other mixed-conifer forest types, where historic fires burned at intervals ranging from 2-30 years. After nearly a century of fire regime disruption, many of these forests are characterized by relatively dense canopy cover and sparse understory vegetation. Results from monitoring plots located in at least 8 different fires in the giant sequoia mixed-conifer forest, indicate that mean percent cover of understory vegetation increased slightly over the ten years following fire, while species richness more than doubled over this same period of time. One new species was non-native but only occurred in small numbers in one plot. Although they are small components of total cover, mean percent cover of forbs triples and shrub cover more than doubles following fire treatments. Shrub species dominance shifts from Chrysolepis sempervirens (bush chinquapin) pre-burn to Ceanothus parvifolius (little-leaved ceanothus) ten years after fire. While objectives currently focus on reducing fuels and restoring stand structure, prescribed fire may also help restore understory vegetation diversity by providing conditions favorable to many of the fire-adapted plant species in these forests.