Effect of fire on grasses in central semi-arid Argentina

The objective of this work was to study the effects of different fire intensities and season of burning on six important grass species in the Caldenal. Stipa gynerioides and S. speciosa, two grasses not readily consumed by cattle, were sensitive to fire severity. A high severity fire in January killed almost 86% and 66% of these two species, respectively, whereas a moderate severity fire after rain in April killed only 2.5% of the individuals. Fire reduced basal diameters and percent foliar cover in these two species. Mortality rates for S. tenuis (20-38%), S. longiglumis (15-20%), Piptochaetium napostaense (12-28%) and Poa ligularis (17-22%) species that are heavily grazed by cattle, indicated that they were less sensitive to fire than were the other grasses. Fire, and probably the combined effect of fire and rest from grazing, increased basal diameters and percent foliar cover in the latter species. (C) 1996 Academic Press Limited