Revegetação de área degradada da caatinga por meio da semeadura ou transplantio de mudas de espécies arbóreas em substrato enriquecido com matéria orgânica.

Abstract

Caatinga exploration is based on subsistence agriculture, extensive cattle raising and logging for energy production. These actions and the tropical dry climate result in large areas with no vegetation cover and high levels of degradation. Two experiments were carried out at Fazenda NUPEARIDO/UFCG in Patos (PB) to test forest practices to revert this situation. The first one evaluated the addition of bovine manure and sowing the native tree species Mimosa tenuiflora, Caesalpinia pyramidalis, Anadenanthera macrocarpa and Tabebuia caraiba on re-vegetation of a degraded area. The 2x2 factorial treatments (factor 1: zero or the addition of the equivalent to 120m3 of bovine manure per hectare, and factor 2: no seeding or sowing of the equivalent to 14 million seeds/ha) were randomly assigned to 0.25m2 square plots according to a randomized block design with two treatment replications in each block. The plots were subdivided in time (March, July and November 2006, March 2007, and March 2008). Manure addition and sowing of these species showed to be unviable, as no plantule established and persisted in the area for more than a year. The second experiment tested the addition of organic matter on natural regeneration of native tree species, and the potential of re-vegetation of degraded areas by planting M. tenuiflora and C. pyramidalis in manureenriched burrows. This experiment was carried out according to a randomized block design, with four treatments (T0- no burrow, no manure addition, and no seedling plantation; T1- burrows with manure-enriched substratum, and no seedling plantation; T2- burrows with manure-enriched substratum, and M. tenuiflora seedling plantation; and T3- burrows with manure-enriched substratum, and C. pyramidalis seedling plantation), six blocks and two treatment replications per block. The plots were subdivides in time (April 1, July 12 and November 25, 2005). There were nine 0.3x0.3x0.3m3 burrows equally spaced in the 9x9m2 experimental plots. Data on survival and seedling development were collected from April 2005 to June 2008. No natural regeneration of tree species was observed in the plots in T0 and T1 plots. In June 2008, 3 and 64 plants of, respectively, C. pyramidalis and M. tenuiflora (2% and 36% of the planted seedlings, respectively). At this time, these M. tenuiflora plants reached a mean height and basal diameter of 177.7 cm/plant and 24.8 mm/plant, respectively. These plants corresponded to 658 M. tenuiflora individuals/hectare, while natural regeneration observed outside the plots in the experimental period corresponded to 24 M. tenuiflora plants/hectare. The conclusions are that the localized addition of organic matter did not result in natural regeneration of tree species in this caatinga degraded area, and revegetation can be abbreviated by planting M. tenuiflora into burrows enriched with organic matter. Planting of C. pyramidalis seedlings showed unsatisfactory results. The expectations are that these findings can help all those people interested in re-vegetation of degraded areas of caatinga, and encourage to further proceed in that issue in order to develop a complete set of management practices to make possible the regeneration of many degraded areas of the caatinga in the near future.