Avaliação das Parcelas Permanentes de Monitoramento (PPM's) em Florestas Secundárias de Idades Distintas no Nordeste Paraense (Bragança).

Abstract

Secondary succession is an anthropic process that has been intensifying in Brazil, due to the rapid increase in the removal of primary vegetation for various purposes such as agriculture and cattle ranching among other forms, especially in the Amazon region. The management of secondary forests (capoeiras) can be an alternative for land use, but little is known about this practice. The practice of monitoring permanent monitoring plots (PPM's) provides knowledge of the dynamics of vegetation assisting in decisions for future treatments for management. This study was developed with the objective of analyzing and evaluating the behavior of tree stratum species in secondary vegetation of different ages, such as abundance, growth, recruitment and mortality. Six 50x50 m PPM's were installed, subdivided into 25 subplots of 10xl0 m in two areas of approximately 35 and 45 years in Bragança, Pará, where individuals with dHAPe "5 cm were measured. The diametric distribution of the species was negative exponential and the Sorensen index was 0.63. The 35 year old stand had a diameter distribution of 0.5 cm. The 35 year old stand had an average increment of 0.30 cm/ha/year, and the 45 year old stand had 0.34 cm/ha/year. The species that increased the most in the 35 year old area were Franchetella gongrojpii, Pterocarpus amazonicus and Jacaranda copaia, and in the 45 year old were Byrsonima crispa, Diplotropis guianensis and Sclerolobium chrysophyllum. The 35 year old forest had the highest number of newcomers (169 individuals) and the lowest mortality (253 individuals) in relation to the 45 year old forest (111 newcomers and 511 dead) during six years of measurements. The areas presented a high floristic similarity and a distribution characteristic for management. Regarding the dynamics, the different increment of species may be a consequence of the land use that preceded the current succession. The vegetation of older age has few individuals entering in relation to the younger vegetation, which may be a consequence of higher density of the forest canopy, which may have caused the low mortality of younger vegetation, i.e., the radiation inside the forest is a factor for the mortality and entry of individuals.