Comparação entre estratos regenerantes de florestas primária e secundária: uma avaliação da restauração passiva no oeste do Paraná

Abstract

The Atlantic forest biome has been reduced to only 7.4% of its original coverage, being the main reason the human occupation. In the state of Paraná remained, with exception of the vegetation of the Serra do Mar and of the Iguaçu National Park (PNI), few small fragments, which require the increasing of connectivity on a landscape scale, requiring the expansion of native forest cover. This expansion can be through the spontaneous regeneration of native forests, a phenomenon here treated as passive restoration. The objective of this study was to evaluate the regenerative stratum of a secondary forest in passive restoration, site in restoration (pasture abandoned for 25 years), through comparison with the regeneration stratum of primary forest of the PNI, reference site. For this, the attributes considered were structural: density, plant height and diameter at height of soil – DHS; of diversity: species richness and species diversity; functional: frequency distribution of dispersal syndromes for individuals and species and proportion of non pioneer species and of individuals of non pioneer species; and the floristic composition. In each site were demarcated 30 circular plots 10 m2 each and collected data from shrub and tree individuals with DBH < 5 cm and height greater than 50 cm. Botanical samples were collected for later identification in laboratory by comparing with herbarium material. 589 individuals distributed in 43 species were recorded in the restoration site and 831 individuals distributed in 48 species were recorded in the reference site. The most abundant species in the restoration site were Parapiptadenia rigida (Benth.) Brenan and Pombalia bigibbosa (A. St.-Hil.) Paula-Souza, with 236 and 133 individuals, respectively, and the most abundant in the reference site was Sorocea bonplandii (Baill.) W.C. Burger et al. with 182 individuals. Statistically significant differences were found in plant height, density, diversity, representativeness of individuals of zoochoric species, proportion of individuals of non pioneer species and floristic composition. With the exception of the variable plant height which was greater in the restoration site, other quantitative variables had larger values in the reference site. The differences between the sites may be due to some restrictive filters such as more luminosity, greater edge effect, less favorable edaphic conditions and lack of connectivity and of attractive for seed dispersers in the restoration site. We concluded that, after 25 years, the passive restoration process resulted in a forest whose regeneration stratum is still pretty distinct from verified in primary forest, highlighting the importance of the conservation of remnants of primary forest. However, the similarities found denote that the restored forest successional trajectory is appropriate, what, demonstrates a high potential for application of passive restoration in the region of the study areas.