Evaluation of the Management Potential of Timber Resources in Clear-Water Floodplain Forests in the Amazon Using Growth Models

Abstract The Amazonian clear-water igapós are floodplains mainly covered by forests with intermediate hydrochemical and edaphic conditions between the nutrient-rich várzea along white-water rivers and the oligotrophic igapós along black-water rivers. Earlier studies indicate the potential for management of timber species in the várzea due to the fast tree growth and high forest productivity. Timber resource management, however, is not recommended in the black-water ecosystem because of the general slow tree growth and regenerative capacity. For clear-water igapós, information on the potential for sustainable management of timber resources is lacking. In this context, we aimed at modelling tree growth in diameter, height, and volume to derive estimates for potential management criteria (minimum logging diameter - MLD, felling cycle - FC) for eight timber species in the clear-water igapós of the Branco and Tapajós rivers in the northern and southern section of the Amazon basin, respectively. Growth modeling followed the guidelines of the Growth-Oriented Logging concept with an adaptation of diameter growth adjusted by mixed-effect non-linear regression. The studied tree species had MLDs varying from 36 to 90 cm and FCs ranging from 6 to 21 years, contrasting the established standards in forest legislation (MLD: 50 cm; FC: 25-35 years). As clear-water igapós are among the most threatened ecosystems in the Amazon basin due to different land uses (large-scale deforestation, hydropower generation, mining), we recommend testing the management of commercial tree species at a small scale and integrating in conservation units to stepwise promote the sustainable management of these natural resources by traditional communities to increase their welfare and to conserve the ecosystem