Survival of Sprouting Shrubs Following Summer Fire: Effects of Morphological and Spatial Characteristics

Efficacy of fire in reducing shrub density is low in plant communities where most woody plants resprout from stem bases and crowns following fire. Our objective was to determine the relationship of shrub mortality and recovery from summer fire to prefire shrub structural characteristics. A randomized, complete block design with two treatments (burned and control) and three blocks was used in the experiment. Within each block and treatment combination, we randomly selected 40 individuals each of brasil (Condalia hookeri M. C. Johnst.), huisache (Acacia farnesiana L.] Willd.), and spiny hackberry (Celtis ehrenbergiana Klotzsch] Liebm.). We estimated height, canopy diameter, number of stems, stem diameter, and distance to the nearest shrubs before ignition of fires. Fires were ignited during July and August 2001. Survival, sprout number, height, and total plant height were estimated 47–52 wk postburn. Mortality of brasil was 26 times greater on burned sites than on control sites, but mortality of huisache and spiny hackberry was negligible. Mortality of brasil varied from 0% to 68% among blocks. Postburn height and number of sprouts increased with preburn shrub height and number of stems, indicating that longer intervals of time between fires that allow shrub growth facilitate more rapid postfire recovery. Factors other than the preburn shrub structural characteristics we measured appear to influence postfire shrub survival most strongly, although these characteristics are useful in predicting postfire sprout production and shrub height.