Desert Fires Fueled by Native Annual Forbs: Effects of Fire on Communities of Plants and Birds in the Lower Sonoran Desert of Arizona

Abstract

In 2005, fire ignited by humans swept from Yuma Proving Grounds into Kofa National Wildlife Refuge, Arizona, burning ca. 9,255 ha of Wilderness Area. Fuels were predominantly the native forb Plantago ovata. Large fires at low elevations were rare in the 19th and 20th centuries, and fires fueled by native vegetation are undocumented in the southwestern deserts. We estimated the area damaged by fire using Moderate Resolution Imaging Spectroradiometer and Normalized Difference Vegetation Index, which are more accurate and reduce subjectivity of aerial surveys of perimeters of fires. Assemblages of upland and xeroriparian plants lost 91 and 81% of live cover, respectively, in fires. The trees Olneya tesota and Cercidium had high amounts of top-kill. King Valley was an important xeroriparian corridor for birds. Species richness of birds decreased significantly following the fire. Numbers of breeding birds were lower in burned areas of King Valley 3 years post-fire, compared to numbers in nearby but unburned Alamo Wash. Although birds function within a large geographic scale, the extent of this burn still influenced the relative abundance of local species of breeding birds. This suggests that breeding birds respond to conditions of localized burns and slow recovery of vegetation contributes to continued lower numbers of birds in the burned sites in King Valley.