Fecha de aplicación de fuego y diversidad de herbáceas en una sabana de Elionorus muticus (Spreng) O. Kuntze

Fire is both a natural disturbance and a range management tool in the savannas of Elionorus muticus (Spreng) O. Kuntze, of the Chaco region of Argentina. Our objective was to assess the effect of different dates of fire application on the herbaceous diversity of the savanna. Plots were burn at random in four successive dates, in two experiments initiated in 1993 and 1994, respectively. Richness and abundance of grasses and broadleaf species were registered in each plot, before the fire and after three growing seasons from fire. Data were summarized using the Shannon-Wiener diversity index (H'). A variable DeltaH' was defined as the difference between the H' observed before and after the fire for each plot/year, and used as dependent variable in an ANOVA; fire application date, experiment, their interaction and year of observation (t) were considered as independent variables, with a repeated measures approach. Results indicate that although fire increased herbaceous diversity significantly, this general outcome was significantly modified by the date of fire application. This result is attributed to the pre and post fire environmental conditions as well as the phenological status of the species. Fire application at the mid-fire season generates higher diversity than any other time, probably due to plant resistance and better post fire environmental conditions.