Tree species responses of western Amazonian floodplain forests to hydro-geomorphic disturbance as tool for predicting impacts caused through river damming and climate change

点击翻译按钮获取中文摘要

Amazonian floodplain forests along sediment- and nutrient-rich white-water rivers (várzea) are the most species-rich floodplain forests on Earth and provide crucial ecosystem services for large part of Amazonia´s rural population, but their biodiversity and ecological functioning is increasingly threatened through flow regulations as caused by river damming and climate change. While biodiversity, tree species distribution, biomass, growth and primary productivity of várzea forests are relatively well studied in Brazilian lowland Amazonia, significant knowledge gaps exist particularly in the transitional zone between the Andes and the Amazon lowlands (foothill zone), where geomorphic activity of rivers and associated floodplains is extraordinarily high. Because the construction of river dams for hydropower generation is increasing in both the Andes and in the Amazon lowlands, the reaction of the mostly narrowly adapted tree flora to changes in hydrological regimes and associated geomorphic activity is uncertain. Here, we propose to investigate tree species richness, distribution and population structures, as well as flooding-growth responses of Amazonian várzea tree species along the flooding and geomorphic river activity gradients, in three white-water rivers of the Andean-Amazonian transition zone in Bolivia, Southwestern Amazon basin. The species response curves will provide ecological niche models that enable the prediction of tree species optima and niche breadths with reference to occurrence and stem abundance, along the flooding and associated abiotic gradients. The determination of tree ages and of yearly wood increment in selected indicator tree species in addition will provide information on species responses in growth, vitality, productivity, and carbon sequestration. Ultimately, these data shall serve for modelling species and community changes under modified flood pulse regimes in partly or fully dammed Amazonian river basins. Simultaneously, these data will serve as basis to model how modified flood regimes through climate change will affect the floodplain flora, tree species diversity, and forest productivity during the next decades and centuries.