PARENT SESSION
Oral Session #55: Fire Ecology. Presiding: M. Moritz.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas H.

Peak fire temperatures and short-term ecological effects in the Mojave Desert.

Brooks, Matthew¹, ¹

ABSTRACT- Fire has been historically infrequent in the Mojave Desert, resulting in very few studies of its ecological effects. The purpose of this study was to describe seasonal and spatial variations in peak fire temperature, and post-fire properties of annual plants and soils. Peak fire temperatures were measured using temperature indicating paint among seasonal fire treatments (spring, summer), microhabitats created by creosote bush (Larrea tridentata) (beneath-canopy, dripline, interspace), and distances from the soil surface (-2, 0, 5, 10cm). Microhabitat accounted for most of the variation in peak fire temperature (77%). Annual plant biomass, species richness, soil nutrients, and water repellency were measured among fire treatments (spring, summer, unburned) and microhabitats. Burn treatments compared to unburned controls accounted for most of the post-fire variation in annual plant biomass (20%) and species richness (19%) during four post-fire years. Fires decreased biomass of an invasive annual grass (Bromus rubens), increased biomass of another invasive annual grass (Schismus spp.) and an invasive forb (Erodium cicutarium), and had variable effects on native annual plants. Fire treatments did not significantly affect soil water repellency or phosphorous levels, but did slightly increase nitrogen levels in the dripline microhabitat during the first post-fire year. These results indicate that fire temperatures and effects can be highly variable and models of post-fire succession must account for variation among microhabitats and annual plant taxa in the Mojave Desert.

KEY WORDS: annual plants, soil nutrients, disturbance ecology, invasive species