Revegetação de áreas antropizadas da Caatinga com espécies nativas.

Abstract

Humans exploit natural resources to satisfy their needs, and very often this exploitation causes environmental degradation, which is more intense in tropical countries. Inadequate natural resources exploration has caused serious environmental damages in Northeastern Brazil, especially in Paraíba, where more than 50% of its territory present high levels of degradation and need attention to improve vegetation cover. The re-establishment of tree species is fundamental for land reclamation in this ecosystem increase vegetation cover in degraded areas, which can be accelerated by planting of Caesalpinia pyramidalis, Mimosa tenuiflora and Cnidoscolus phyllacanthus, pioneer species of antropized Caatinga sites (ACS). These tree species yield firewood and/or forage, protect the soil and ameliorate site conditions for the development of the herbaceous layer. This study evaluated the survival and the initial growth of these tree species in two ACS, and their effects on the recovery of the herbaceous layer. Data were collected from September/2008 to October/2009, in Patos-PB, in two ACS due to tree logging and overgrazing. The ACS were fenced and received goat manure and fertilizer before planting the seedlings in 36-pit plots according to a randomized complete block design with five treatments (control, and planting of C. pyramidalis, M. tenuiflora and C. phyllacanthus in pure or intercropping systems) and five replications in 144m2 square plots. At the end of the first growing season, more than 90% of the seedlings planted survived, and maximum mean height, basal diameter and soil herb and tree cover reached 219cm, 26mm, 100%, and 50%, respectively, with M. tenuiflora showing the highest performance among the tree species. The trees did not affect the herbaceous layer, in which two Sida species predominated, although diversity and forage production improved toward the end of the growth season. Herbaceous dry biomass production averaged 3ton/ha (1:2 monocotyledonous:dicotyledonous weight ratio) and showed NDF, ADF, crude protein and ash contents within values reported in the literature, except for the higher FDN values shown by monocotyledonous plants (>74.5%). Fast revegetation of antropized Caatinga sites with herbaceous and tree species can be attained by fencing and planting of native tree species, especially M. tenuiflora, into pits of convenient dimensions and fertilization levels.