Amazonian flood impacts on managed Brazilnut stands along Brazil's Madeira River: A sustainable forest management system threatened by climate change

Abstract

Impact of flooding on tropical forest ecosystems and their management is a little-studied area that is expected to become increasingly important under projected climate change. A demonstration of this was provided by the record-breaking 2014 flood of the Madeira River in Brazil. We assessed factors affecting survival of Brazilnut trees (Bertholletia excelsa H.B.K.) under root asphyxia caused by flooding in the Lago do Capanã Grande Extractive Reserve in Manicoré municipality (county), Amazonas state, Brazil. Mortality was surveyed in three Brazilnut groves (castanhais) in 680 individual Brazilnut trees of which 357 had been exposed to flooding and 200 had been flooded for at least 83 days, which was the threshold for mortality effects. Trees were georeferenced and measured for DBH and the height above the ground of the flood-water mark. This information, together with topography from satellite data and water levels from hydrographic gauges, allowed calculation of the time each tree was flooded. None of the 323 unflooded trees died. The analysis indicates a relationship between mortality and duration of root asphyxia, killing 17% of the individuals exposed to flooding and 35% of the individuals that were flooded for periods greater than 109 days. Nevertheless, survival exceeded 50% for all flooding durations. The data suggest that larger trees have a greater probability of mortality for any given period of asphyxia. Expected increases in extreme flood events threaten a sustainable forest management system based on harvest of non-timber products. © 2017 Elsevier B.V.