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

沿泥沙和营养丰富的白水河(várzea)的亚马逊泛滥平原森林是地球上物种最丰富的泛滥平原森林，为亚马逊的大部分S农村人口提供重要的生态系统服务，但由于河流筑坝和气候变化导致的流量调节，其生物多样性和生态功能受到越来越大的威胁。虽然在巴西低地亚马逊地区对瓦泽亚森林的生物多样性、树种分布、生物量、生长和初级生产力进行了较好的研究，但在安第斯山脉和亚马逊低地之间的过渡地带(山麓地带)存在着重大的知识差距，那里的河流和相关泛滥平原的地貌活跃度非常高。由于在安第斯山脉和亚马孙低地建造水力发电的河坝越来越多，适应范围较窄的树木区系对水文状况和相关地貌活动的变化的反应是不确定的。在这里，我们建议调查亚马逊盆地西南部玻利维亚安第斯-亚马逊过渡带三条白水河流中亚马逊树种的物种丰富度、分布和种群结构，以及沿洪水和地貌河流活动梯度的亚马逊树种对洪水-生长的响应。物种响应曲线将提供生态位模型，从而能够参照洪水和相关的非生物梯度，根据发生情况和树干丰度来预测树种的最佳生态位宽度。此外，确定选定指示树种的树龄和年木材生长量还将提供有关树种在生长、活力、生产力和碳固存方面的反应的信息。最终，这些数据将用于模拟部分或全部筑坝的亚马逊河流域在修改洪水脉冲制度下的物种和群落变化。同时，这些数据将作为模拟未来几十年和几个世纪内通过气候变化改变的洪水制度将如何影响洪泛区植物、树木物种多样性和森林生产力的基础。

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.