Composição e diversidade florístico-estrutural de um hectare de floresta densa de terra firme na Amazônia Central, Amazonas, Brasil / Composition and floristic-structural diversity of a hectare of terra firme dense forest in Central Amazonia, Amazonas, Brazil

Foram inventariadas todas as árvores, lianas e palmeiras com DAP > 10 cm de um hectare (dois transectos paralelos de 500 x 10 m) de floresta densa de terra firme sobre platô de Latossolo, 90 km a nordeste de Manaus (02º35'45" S e 60º12'40" W). A fitofisionomia local é exuberante e homogênea, com grande número de árvores altas e finas. Foram encontrados 670 indivíduos distribuídos em 48 famílias, 133 gêneros e 245 espécies. Do total amostrado, 70 por cento ou 467 indivíduos apresentaram DAP < 22,1 cm. Abarema mataybifolia (Sandw.) Barneby & Grimes, Leonia glycycarpa Ruiz & Pav., Swartzia reticulata Ducke e Aspidosperma oblongum A. DC., foram as únicas espécies a apresentarem valores superiores a 90 cm de DAP. Fabaceae, Sapotaceae e Lecythidaceae constituíram as três famílias com maior riqueza de espécies e maiores índices de valor de importância aos níveis de família e espécie. Os índices de diversidade (H" = 5,1) e de equitabilidade (E" = 0,92), ambos de Shannon-Wiener, indicam que a floresta é bem diversificada, com uma abundância relativamente uniforme das espécies. Nesse ambiente florestal, as espécies não tem distribuição espacial uniforme, porém, quanto menor a distância geográfica entre as subparcelas, maior sua similaridade florística (teste de Mantel, p<0,001).

To investigate the composition and floristic diversity of one hectare of a dense forest on a terra firme oxisol plateau, 90 km from the Manaus (02º35"45" S e 60º12"40" W), all trees, lianas and palm trees with diameter at breast height (DBH) > 10 cm were inventoried along two parallel transects of 500 x 10 m. The landscape is vegetationally exuberant and homogeneous, with a large quantity of tall slender trees. A total of 670 individuals in 48 families, 133 genera and 245 species were registered in this floristic inventory. 467 of the plants sampled exhibited DBH < 22.1 cm, representing 70 percent of the total. Abarema mataybifolia (Sandw.) Barneby & Grimes, Leonia glycycarpa Ruiz & Pav., Swartzia reticulata Ducke and Aspidosperma oblongum A. DC. were the species with DBH > 90 cm. Families with greatest species richness and importance value were Fabaceae, Sapotaceae and Lecythidaceae. The Shannon-Wiener diversity (H" = 5.1) and evenness (E" = 0.92) indices suggest that the forest environment is very diversified, but with a relative uniformity of species. However, a uniform spatial distribution of the species in this forest environment was not observed. According to Mantel"s test (p < 0.001), the highest floristic similarity is a function of geographic proximity among suplots.

Modelling Amazonian forest eddy covariance data: a comparison of big leaf versus sun/shade models for the C-14 tower at Manaus I. Canopy photosynthesis

In this study, we concentrate on modelling gross primary productivity using two simple approaches to simulate canopy photosynthesis: "big leaf" and "sun/shade" models. Two approaches for calibration are used: scaling up of canopy photosynthetic parameters from the leaf to the canopy level and fitting canopy biochemistry to eddy covariance fluxes. Validation of the models is achieved by using eddy covariance data from the LBA site C14. Comparing the performance of both models we conclude that numerically (in terms of goodness of fit) and qualitatively, (in terms of residual response to different environmental variables) sun/shade does a better job. Compared to the sun/shade model, the big leaf model shows a lower goodness of fit and fails to respond to variations in the diffuse fraction, also having skewed responses to temperature and VPD. The separate treatment of sun and shade leaves in combination with the separation of the incoming light into direct beam and diffuse make sun/shade a strong modelling tool that catches more of the observed variability in canopy fluxes as measured by eddy covariance. In conclusion, the sun/shade approach is a relatively simple and effective tool for modelling photosynthetic carbon uptake that could be easily included in many terrestrial carbon models.