Successional Differentiation in Structure, Floristic Composition and Wood Increment of Whatewater Floodplain Forests in Central Amazonia

Growth rates of stands and tree species are a basic information for the development of sustainable management plans in tropical rainforests. In Central Amazonian floodplains the growth rhythm of trees is triggered by the annual long-term flooding, which results in a cambial dormancy and the formation of annual tree rings. This allows the determination of tree ages and growth rates. In the Mamairauá Sustainable Development Reserve (MSDR), located in the Amazon state of Brazil, we studied various successional stages in their canopy structure, floristic composition and annual wood biomass production. All trees = 10 cm diameter at breast height (dbh) were investigated in plots differing in size by several parameters like tree species, dbh, tree height, crown area and crown exposure. From each tree cores were sampled to determine wood density, tree age and mean radial increment. Additional cross-sections were taken at different tree heights to model cumulative diameter growth and height growth of the most important tree species. The results show changes along the successional development which incorporates a increasing number of tree species, a decreasing tree density, and dynamical changes in the canopy structure. Wood density increases considerably along the chronosequence leading to an accumulation of above-ground wood biomass, but can not compensate the declining radial and volume increment which results in a lower mean biomass production. The volume increment and biomass production of softwood tree species in the early succession vary significantly from those of densewood timber species in the mature forests. There is a urgent need to consider differences in the growth behavior of tree species to guarantee the sustainability of a forest management as it is planned in MSD