Instituto de Geosciências, Universidade Federal do Pará, Belém, Brasil.
Department of Geography, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
Glob Chang Biol. 2018 Jan;24(1):249-258. doi: 10.1111/gcb.13851. Epub 2017 Sep 1.
Transpiration from the Amazon rainforest generates an essential water source at a global and local scale. However, changes in rainforest function with climate change can disrupt this process, causing significant reductions in precipitation across Amazonia, and potentially at a global scale. We report the only study of forest transpiration following a long-term (>10 year) experimental drought treatment in Amazonian forest. After 15 years of receiving half the normal rainfall, drought-related tree mortality caused total forest transpiration to decrease by 30%. However, the surviving droughted trees maintained or increased transpiration because of reduced competition for water and increased light availability, which is consistent with increased growth rates. Consequently, the amount of water supplied as rainfall reaching the soil and directly recycled as transpiration increased to 100%. This value was 25% greater than for adjacent nondroughted forest. If these drought conditions were accompanied by a modest increase in temperature (e.g., 1.5°C), water demand would exceed supply, making the forest more prone to increased tree mortality.
亚马逊雨林的蒸腾作用从全球和局部尺度上产生了重要的水源。然而，随着气候变化，雨林功能的变化可能会破坏这一过程，导致亚马逊地区乃至全球范围的降水量显著减少。我们报告了唯一一项关于亚马逊雨林森林蒸腾作用的研究，该研究是在长期（>10 年）实验干旱处理后进行的。在接受正常降雨量的一半 15 年后，与干旱相关的树木死亡导致森林总蒸腾作用减少了 30%。然而，幸存下来的干旱树木通过减少对水的竞争和增加光的可用性来维持或增加蒸腾作用，这与生长速率的增加是一致的。因此，到达土壤的作为降雨的水量和直接作为蒸腾作用回收的水量增加到 100%。这个值比相邻的未干旱森林高出 25%。如果这些干旱条件伴随着适度的温度升高（例如 1.5°C），水的需求将超过供应，使森林更容易发生树木死亡增加。
