Produtividade de florestas num gradiente hídrico no interflúvio Purús Madeira

Abstract

The ongoing demand for information of forest productivity has increased the number of permanent monitoring plots across the Amazon. Those plots, however, do not comprise the whole diversity of forest types in the Amazon. In this study we estimate wood biomass productivity was estimated and related to hydrological and edaphic conditions. Forest productivity was estimated by a combination of tree-ring data and allometric equations for biomass estimation for eight plots distributed along 600 km on the Purus-Madeira interfluvial area that is crossed by the BR-319 highway, and related to hydrological and edaphic conditions. Estimated mean productivity was5.6±1.1 Mgha-1year-1. There was a strong relationship between tree age and diameter, as well as between mean diameter increment and mean wood density of the plot. Wood biomass productivity was positively related to soil water saturation and negatively related to the iron content on the shallow surface of the soil. Also, the mean plot age was negatively related to the soil water saturation condition. Three hypotheses were raised to explain these results: (1) the reduction of iron molecules on the saturated soils with plinthite layers close to the surface leaves available phosphorous for the plants; (2) the poor structure of the saturated soils creates an environmental filter selecting tree species of faster growth rates and shorter life spans and (3) the plants on saturated soil are favored during the dry season, by not having restrictions in soil water availability.