Distribuição espacial de espécies madeireiras de interesse comercial manejadas na Reserva de Desenvolvimento Sustentável Mamirauá no Médio Solimões, Amazônia Central

Abstract

Forests located in flooded areas represent 5 to 10% of the Amazon Basin and are generally situated along the margins of large rivers. White-water Amazonian floodplains, várzeas, cover aproximately 200,000 km,2 and are periodically flooded by white or muddy waters of the Amazon River and its affluents. Timber activites in várzea forests are restricted to a few species. The absence of data regarding regeneration and growth linked to inadequate timber exploration has led to the reduction of the population of some species, which have practically disappeared from local markets. To ensure the sustainability of várzea forests it is therefore necessary to understand patterns of spatial distribution of plant species. The general objective of this study was to characterize the spatial distribution patterns of commercial tree species, Ocotea cymbarum, Hura crepitans, Piranhea trifoliata, Eschweilera ovalifolia, Pouteria procera, Terminalia dichotoma, Vatairea guianensis and Macrolobium acaciifolium, managed by community residents of the Mamirauá Sustainable Development Reserve, state of Amazonas. The present study was developed in an area of várzea forest measuring 21.38 ha (02º 45 32,060 S, 64º 53 31,862 W), located in the Mamirauá Sustainable Development Reserve. Comercial species, those with comercial potentional and ecological interest as well asbouyant species were inventoried and measured. Species included in inventories had circumferences of DBA ≥ 78 cm. Parameters of florestic composition, species diversity and equability, mixture quotient, horizontal structure: abundance, dominance and frequency, IVI, IVC and IVIF were evaluated. The parameters of basal area, diametric distribution and patterns of spatial distribution with Payandeh, MacGuinnes, Morisita and Ripley K Fucution were analyzed in this study. Eight-hundred and sixty one individuals belonging to 39 species, 17 families, and 31 genera were registered within the 21.38 ha study area. The richest botanical family was Lauraceae and the most dense was Euphorbiaceae. The most important species is Ocotea cymbarum. The study area demonstrated low heterogeneity with a quotient of 1:22 and low species diversity with (H ) 2,98 e (J ) 0,81. Phytosociological analyses of sampled species revealed that 10 species with the greatest Indices of Importance Values (IVI) represent more than 70.38% of individuals sampled in the community. The 21.38 ha presented 322.79 m² of basal area with an average of 15.10 m²/ha, and the species Hura crepitans was the most representative with 41.45 m². The diametric area distribution presented an inverted J formation with major concentrations of individuals in the first age classes, gradually declining in other classes. By way of the Payandeh and MacGuinnes indices it was possible to determine that large portions of sampled species showed a distribution pattern with a grouping tendency, and that by way of the Morisita Index, the majority showed an aggregate pattern. However, analyzed via K Ripley Funcution, the pattern was predominately random.