EFFECT OF FIRE INTENSITY ON BUD VIABILITY OF 3 GRASS SPECIES NATIVE TO CENTRAL SEMIARID ARGENTINA

The effect of fire on axillary bud viability of Stipa tenuis, Piptocha etium napostaense, and Stipa gynerioides, three important native peren nial grasses in the semi-arid region of central Argentina, was studied under different fire intensities: 300-400 degrees C (low fire intensi ty), 500-600 degrees C (high fire intensity) and no fire (control). Fi re treatments were applied in April 1994 and May 1995 with a portable propane plant burner. After each burn the number of dead buds of S. gy nerioides was higher (p < 0.05) at the centre of the plants than at th e periphery. Stipa tenuis showed a similar response with the exception of the 1995 high intensity treatment. No differences (p > 0.05) in mo rtality were detected between buds located at the centre of the plants and those at the periphery for P. napostaense in either burn. In gene ral, 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 simil ar in S. tenuis, P. napostaense and S. 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 co ntrol plants. Within each fire intensity treatment during both study p eriods there were no statistical differences (p > 0.05) among species in the number of total, metabolically active, dormant and dead buds. T hese results would suggest that fire limits postfire regrowth of S. te nuis, P. napostaense and S. gynerioides. (C) 1997 Academic Press Limit ed.