Effect of fire intensity on bud viability of three grass species native to central semi-arid Argentina

The effect of fire on axillary bud viability ofStipa tenuis, Piptochaetium napostaense, andStipa gynerioides, three important native perennial grasses in the semi-arid region of central Argentina, was studied under different fire intensities: 300–400°C (low fire intensity), 500–600°C (high fire intensity) and no fire (control). Fire treatments were applied in April 1994 and May 1995 with a portable propane plant burner. After each burn the number of dead buds ofS. gynerioideswas higher (p< 0·05) at the centre of the plants than at the periphery.Stipa tenuisshowed a similar response with the exception of the 1995 high intensity treatment. No differences (p> 0·05) in mortality were detected between buds located at the centre of the plants and those at the periphery forP. napostaensein either burn. In general, the number of dead buds in the high fire intensity treatment was slightly higher than the number of dead buds in the low fire intensity treatment in all of the studied species. Treatment effects were similar inS. tenuis, P. napostaenseandS. gynerioides. After each burning date, tillers of plants exposed to fire had more (p< 0·05) dead buds and fewer (p< 0·05) metabolically active buds than the tillers of control plants. Within each fire intensity treatment during both study periods there were no statistical differences (p> 0·05) among species in the number of total, metabolically active, dormant and dead buds. These results would suggest that fire limits postfire regrowth ofS. tenuis, P. napostaenseandS. gynerioides.