Efeito da transposicao de topsoil e mulching de Copernicia prunifera (Mill.) HEMoore na revegetacao de area degradada na Caatinga

The picarra -gravel-mining (subsoil material composed mainly of silt, sand and gravel) takes place in numerous small deposits in Rio Grande do Norte State in order to meet the activities of onshore oil production. At the end of the exploration cycle, the deposits must undergo interventions to rectify and revegetate the landscape. In this study, the efficiency of revegetation techniques was evaluated in an area degraded by picarra exploitation, located in the municipality of Pendencias-RN, in the Tropical Dry Forest (Caatinga). In a split-plot experiment, the effect of topsoil application (in plots), and planting of seedlings (split plots) was evaluated according to the following treatments: T1 - without plantingofseedlings (control); T2 - planting of 15 native tree species and T3 - planting of the 15 species with the application of mulch of the Brazilian palm tree Copernicia prunifera (Mill.) at the base of the plants. Biometric evaluations were performed at 6, 13 and 23 months after planting. Ofthe 15 species evaluated, Mimosa tenuiflora (Willd.) Poir, Mimosa caesalpiniifolia Benth, Enterolobium contortisiliquum (Vell.) Morong, Piptadenia retusa (Jacq.) P.G. Ribeiro, Seigler & Ebinger, Erythrina velutina Willd, Cenostigma pyramidale (Tul.) Gagnon & G.P.Lewis,Jatropha molissima (Pohl) Baill. and Tabebuia aurea (Silva Manso) Benth. & Hook.f. ex S.Moore stood out for their high survival and growth, indicating suitability for the use in the rehabilitation of areas degraded by picarra - gravel-extraction. The addition of topsoil to the degraded substrate did not affect the survival rate or plant height. Topsoil, however, promoted better vegetation cover (75% a 100% of coverage vs. 5% to 25% in the control treatment; p<0.05), and greater biodiversity of regenerating herbaceous species. Mulching promoted greater growth of tree species at 13 months when in the presence of topsoil (113 cm average height vs. 93 cm in the control; p<0.05), and the canopy area of the plants at 23 months (0.30 m2 in diameter vs 0.20 m2; p<0.05). The results indicate that the combination of topsoil application, planting of seedlings of selected species and application of mulching to the base of tree seedlings is an efficient strategy for the recovery of areas degraded by mining in the Caatinga.