摘要：The impacts of fire on creosote bush scrub vegetation have received attention recently as fire has become locally common throughout the Mojave and Sonoran deserts. One area of particular concern is western Coachella Valley, which forms the northwestern extent of the Colorado Desert. This is a major wildland-urban interface area that has been significantly impacted by atmospheric nitrogen deposition concomitant with fuel alterations from invasive annual grasses and increased ignition frequencies from human activities. Creosote bush scrub takes much longer than more mesic vegetation types to re-establish after fire, and the majority of desert species lack traits associated with resiliency to fire disturbance. Previous research in this area has only investigated once-burned stands for up to five years since fire. This study documents perennial vegetation from seven sites that represent a 2- to 28-year-old fire chronosequence. Our surveys revealed that fire significantly reduced shrub richness and diversity regardless of time since fire. Total shrub cover and density returned to or exceeded unburned levels at least 20 years after fire, although species composition was almost entirely brittlebush ( Encelia farinosa ), a shortlived shrub. Longer-lived shrubs indicative of unburned vegetation, such as creosote ( Larrea tridentata ), white bursage ( Ambrosia dumosa ), and white ratany ( Krameria grayi ), failed to recover. Shrub plus cacti richness and diversity were lower in burned stands regardless of time since fire. Encelia shrublands may form an alternate stable state following fire in this region.
