| Daniel V. Peláez, Roberto M. Bóo, Mirta D. Mayor, and Omar R. Elia |
| Authors are professor and researcher, Departamento de Agronomía (UNS) and Comisión de Investigaciones Científicas (CIC); professor and researcher, Departamento de Agronomía (UNS) and Comisión de Investigaciones Científicas (CIC); professor, Departamento de Agronomía (UNS); research technician, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Departamento de Agronomía, Universidad Nacional del Sur, (8000) Bahía Blanca, Argentina. |
Abstract |
| Fire is a key factor in the temperate semiarid region of central Argentina. The objectives of this work were to evaluate the effect of different fire intensities applied during different seasons under field conditions on the mortality of Piptochaetium napostaense (Speg.) Hack, Stipa tenuis Phil., and Stipa gynerioides Phil., 3 of the dominant grasses within the region and to determine their thermal death points in the laboratory. Ten plants of each species were exposed to low fire intensity (300–400°C), high fire intensity (500–600°C), and no fire (control) in April and December 1994, May 1995, and January 1996. Fire treatments were applied with a portable propane plant burner. The thermal death point was determined (during fall and spring) using the Wright's technique. Although mortality with high fire intensity was always higher than mortality with low fire intensity for all species, differences were not significant (p > 0.05). Pooling both treatments, the highest (p < 0.05) average mortality for P. napostaense (55%) and S. tenuis (85%) was observed after the May burn. Average mortality for S. gynerioides was similar (p > 0.05) for all burning dates. Only after the May burn, was average mortality of P. napostaense and S. tenuis higher (p < 0.05) than average mortality of S. gynerioides. The thermal death point was similar in all studied species. It was 65°C during the fall, and 68°C during the summer. This could explain, at least in part, similar mortalities (except after the May burn) between species and the date of burning found in this study. |
| Key Words: fire mortality, fire intensity, thermal death point, Piptochaetium napostaense (Speg.) Hack, Stipa tenuis Phil., Stipa gynerioides Phil. |