| Resumo: |
As experiment was conducted at the Fazenda Experimental do Vale do Curu, Pentecoste county, Ceará, Brazil, on the transition between the Litoral and Sertão regions, with the objective of evaluating the effects of the different densities, or crown cover percentages of the ligneous species, of the fire and of the year on the floristic composition, frequency of species and biomass production of herbaceous layer of native ranges. The research extended for a period of two years, begining on September, 1981. The following treatments were tested. Treatment: A - 0, B - 100, C - 200, D - 400, E - 800, T - 8500. Cover (%): A - 0,7, B - 9,2, C - 16,5, D - 21,3, E - 32,2, T - 100,0. The densities above correspond to the number of trees that were left. Samples for the evaluation of the phytossociological parameters of the herbaceous layer were harvested by the end of the rainy seasons, and they consisted of retangular quadrats of 1,0 x 0,5m randomly distributed, being 100 samples for cover percentage, 100 for frequency and 20 for biomass production per subplot. The experiment followed a randomized split plot design with three replications. The density or crown cover constituted the main and fire the subplot. The results indicate that densities or crown cover of the ligneous species and the fire had no significant effects on the total biomass production and frequencies of the herbaceous layer components. However, the year significantly effected the dry matter production. The frequencies and biomass production of the grasses responded to the treatments, while the legumes and other broad leaf forbs did not. The fire did not affect the grass frequencies, but increased their production. The availability of mulch significantly decreased on the burned areas. It is possible that the crown cover percentages tested on this experiment were below the critical levels to affect the sociologic parameters of the herbaceous layer. |
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