Avaliação dos remanescentes florestais da bacia do Rio Itajaí com enfoque em seu potencial de manejo

Abstract

Most of the remaining forests of Santa Catarina, including the Itajai River Basin, are secondary and are, most often, owned by smallholders. Assigning value to these forests, from the possibility of its use to generate income and, therefore, the valuation of forest land is considered a necessary condition to ensure their survival and biodiversity. This thesis aims to evaluate the composition and structure of the remnants of dense rain forest and lower montane Montana Itajai River Basin and identify their potential for management, with logging purposes. The dataset used in this study was provided by Forest Floristic Inventory Project of Santa Catarina (IFFSC) and consists of 80 sampling units of the conglomerate. The groups were composed of four subunits of 20 x 50 m, in which they were raised all individuals with DBH ≥ 10 cm. The regeneration was sampled in 400 m2 within each cluster. The forest structure was characterized by the use of phytosociological parameters and the overall diameter distribution and species. In the submontane forest remnants were found in the tree and the and regeneration stratum, 373 and 397 species respectively, with a mean of 60.3 and 56.1 per sample unit and a mean basal area of 20.2 m2.ha-1. In the montane forests, 440 species occurred in the tree stratum and 400 in regeneration, averaging 60.5 and 44 species per sample unit, respectively, and a basal area of 22.3 m2.ha-1. In order to gather and sample units remaining floristically and structurally similar, we performed a cluster analysis, applying the technique of hierarchical clustering, forming four groups. The four identified groups showed variation in phytosociological parameters of the tree stratum. The number of species varied from 216 to 403, the number of trees per hectare was between 583-709, basal area ranged from 22.53 to 24.14 m2.ha-1 and stem volume was 90.43 to 103.29 m3.ha-1. Considering the species of major importance value and potential for management in each group a 10% reduction of basal area was proposed, through a selective cutting of some trees with larger diameters, both pioneer and early secondary and late secondary species, combined with a refinement thinning of remaining trees to encourage development of potential crop trees. This slight intervention was deemed compatible with the maintenance of diversity and community structure of exploited populations. The management of palm-heart tree Euterpe edulis was considered unfeasible due to the reduction and degradation of their populations found in the sampled forest remnants. At actual price level, raised from sawmills in the study region, the net financial result of this operation varies from R$ 225,70 to R$ 1.908,94 per hectare. The management of the remaining secondary forests of the Atlantic Rain Forest in Itajai River Basin may, thus, contribute to increase the income of forest owners, who are almost always smallholders. A study on the feasibility of the proposed operational management presented will be needed to evaluate the dynamics of the forest after logging, as well as exploitation damages on remaining trees of these forest communities.