Species richness and floristic composition in four hectares in the Jau National Park in upland forests in Central Amazonia

Four hectares were inventoried for all trees with diameter at breast height (DBH) of 10 cm or greater in a terra firme forest 200 km Northeast of Mana us, Central Amazonia. The number of species varied from 137 to 168, the num ber of individuals from 639 to 713, total basal area from 32.8 to 40.2 and total biomass from 405 to 560 tons per hectare. The majority of trees, 90%, had a DBH between 10 and 30 cm. Leguminosae, Lauraceae, Sapotaceae, Chryso balanaceae and Moraceae were the most rich families (number of species) in all sampled hectares. The most abundant families in all sampled hectares (n umber of trees) were Leguminosae, Burseraceae, Myristicaceae, Moraceae and Chrysobalanaceae. The most dominant families in all sampled hectares (basal area and biomass) were Leguminosae, Lecythidaceae, Chrysobalanaceae, Bomba caceae and Moraceae. Similarity indexes at family level varied from 67 to 8 6% between the four hectares sampled. Alexa grandiflora (Leguminosae) was t he most abundant species in the hectares one and three, while Scleronema mi cranthum (Bombacaceae), and Oenocarpus bacaba (Palmae) were the most abunda nt species in hectares two and four. S. micranthum was the most dominant sp ecies (basal area) in hectares one and two, while Bertholletia excelsa (Lec ythidaceae) and Goupia glabra (Celastraceae) were the most dominant species in hectares three and four. S. micranthum (Bombacaceae), Buchenavia sp. 2 (Combretaceae), B. excelsa (Lecythidaceae) Couepia obovata (Chrysobalanacea e) were the most dominant species (biomass) in hectares one to four, respec tively. Similarity indexes at species level varied from 26 to 44% between t he four sampled hectares. This inventory is compared with previous studies and it was found that, in our study area, there was a greater proportion of trees of 60 cm diameter or more and consequently a considerably higher tot al basal area. It is concluded that there are still an inadequate number of inventories of Amazonian terra firme forests to elucidate the major Aorist ic pattern a both regional and local levels. Since the area is a mosaic of distinct floristic communities it is essential to obtain further standardiz ed inventory data in order to set adequate conservation policies for the re gion.