Ecosystem recovery in terra firme forests after cutting and burning: a comparison on species richness, floristic composition and forest structure in the Jau National Park, Amazonia

Six hectares, three in a primary forest and three in a 40 year old secondar y forest were inventoried for all trees with Diameter at Breast Height (DNH ) of 10 cm or greater in a terra firme forest 200 km north-east of Manaus, central Amazonia in order to compare the difference between structure, spec ies richness and Aoristic composition. Both species richness and tree densi ty were significantly higher in the upland forest than in the secondary for est. The forest structure pattern analysed (DBH, basal area and estimated d ry biomass) did not differ significantly between the two forest types. Simi larity indices at species level were only 14%. In the 3 ha of primary fores t the number of species varied from 137 to 159, the number of individuals f rom 639 to 713, total basal area from 32.8 to 40.2 m(2) and estimate total of above-ground dry biomass (AGBM) from 405 to 560 tons per ha. In the 3 ha of secondary forest, the number of species varied from 86 to 90, the numbe r of individuals from 611 to 653, total basal area from 28.8 to 39.9 m(2) a nd estimated total AGBM from 340 to 586 tons per ha. Family Importance Valu e (FIV) is the sum of relative density, dominance and richness of a family. The most important families in relation to FIV were Burseraceae, Chrysobal anaceae, Lecythidaceae, Myristicaceae, Bombacaceae, Fabaceae and Mimosaceae in the 3 ha of primary forest, while Burseraceae, Lecythidaceae, Sapotacea e, Arecaceae and Cecropiaceae were the most important families in the 3 ha of secondary forest. Importance Value Index (IVI) is the sum of relative de nsity, dominance and frequency of a species. Aba grandiflora (Caesalpiniace ae), Scleronema micranthum (Bombacaceae) and Pourouma guianensis (Cecropiac eae) were the most important species in relation IVI, in the primary forest , while Eschweilera grandiflora (Lecythidaceae), Protium apiculatum (Burser aceae) and Bertholletia excelsa (Lecythidaceae) were the most important spe cies in the secondary forest. We conclude that species richness was signifi cantly different between the two forests, but that forest structure pattern s analysed in this study (DBH, basal area and dry biomass) were similar. Th is demonstrates that 40 years was sufficient time for the secondary forest to recover the original structure of the primary forest, but not the origin al species richness. The low species similarity between the two forests ind icates that the floristic composition was quite distinct and that the mixtu re of primary forest and disturbed forest has led to an increase in total s pecies diversity. (C) 1999 The Linnean Society of London.