PARENT SESSION
Poster Session #59: Fire Ecology II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Fire frequency effects on vegetation structure in shortgrass prairie.

Puttere, Jennifer^*,1, Abbott, Laurie¹, ¹ New Mexico State University, Las Cruces, NM

ABSTRACT- Prescribed fire is an effective tool to control invasive species and alter species composition in many grassland systems. Management strategies using fire require an understanding of the impacts of repeated fires on systems. Fire frequency effects on tallgrass and mixed grass prairies are well-documented, yet impacts of repeated fires on shortgrass prairie have received little study. We report fire frequency effects on vegetation structure in shortgrass prairie in central New Mexico. Between 1991 and 1998, 20m X 25m plots were burned zero, one, two or four times; each fire treatment was replicated in three plots at each of two sites. Aboveground herbaceous production, ground cover, woody plant cover, and species composition was measured in August-September 2001. Harvested herbaceous biomass was separated into three groups (Bouteloua gracilis, all other grasses, and herbaceous dicots). Data were analyzed using ANOVA to determine treatment effects ( = 0.05). Total production did not vary with burn treatments (875 ± 58 kg/ha); however production of herbaceous dicots on plots burned 4 times (807 ± 134 kg/ha) was greater than that on unburned plots (513 ± 89 kg/ha); total grass production on unburned plots (313 ± 63 kg/ha) was nearly 3 times that of plots burned 4 times (106 ± 26 kg/ha). Percent bare ground increased with burning frequency; bare ground in plots burned zero, one, two, and four times was 32.7%, 40%, 51.2%, and 55.4%, respectively. Cover of live vegetation was likely reduced by 2-year drought, and did not vary with burn treatment (4.4%). Litter cover varied from 40.1% in plots burned four times to 62.5% in unburned plots. Woody plant cover was affected by a site by treatment interaction. Woody plant cover did not vary among burned plots; unburned treatments differed between sites (2.3% vs. 10.6%). Species composition data will also be presented.

KEY WORDS: fire frequency, Bouteloua gracilis, drought