Long-term effects of a summer fire on desert grassland plant demographics in New Mexico

Plant demographic responses to an experimental summer fire were monitored for 12 yr on the Sevilleta National Wildlife Refuge, New Mexico, to determine recovery rates of burned plants and evaluate fire effectiveness in preventing shrub invasion of desert grasslands. Fourteen common species of grasses, shrubs, yucca, and cacti were measured for mortality, resprouting, regrowth, herbivory, and reproduction. After the first postfire growing season, black grama (Bouteloua eriopoda [Torr.] Tort.) declined 80% in size, whereas blue grama (Bouteloua gracilis [Willd. ex Kunth] Lag. ex Griffiths) exhibited no decline. Linear regression indicated that B. eriopoda needed 11 yr to recover. Spike dropseed (Sporobolus contractus A.S. Hitchc.) and purple three-awn (Aristida purpurea Nutt.) showed postfire declines in plant sizes, requiring 4- and > 5-yr recovery times, respectively. Sand muhly (Muhlenbergia arenicola Buckl.) exhibited no fire impact. Snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby) sustained 61% fire mortality and reduction in regrowth canopy size. Creosotebush (Larrea tridentata [Sesse & Moc. ex DC.] Coville) had 12% mortality, but survivors recovered over 12 yr. Fourwing saltbush (Atriplex canescens [Pursh] Nutt.) sustained 62% mortality, but recovered plant size in 5-6 yr. Winterfat (Krascbeninnikovia lanata [Pursh] A. D. J. Meeuse & Smit) suffered 7% mortality, but required 9+ yr to recover. Pale desert-thorn (Lycium pallidum Miers) survived fire, recovering prefire canopy size in 3 yr. Torrey joint-fir (Ephedra torreyana Watson) exhibited < 1% mortality, and recovered in 2-3 yr. Soapweed yucca (Yucca glauca Nutt.) had < 2% mortality, recovered plant sizes in 2 yr, and increased numbers of rosettes 17%. Chollas (Opuntia imbricata [Haw.] DC. and Opuntia clavata Engelm.) suffered high mortality rates and required > 12 yr recovery times. Results demonstrated that summer fire may counter some shrub and cacti invasion in central New Mexico, but once shrubs mature, fire is less effective in removing woody plants to restore southwestern grasslands.