3 years ago

Stand dynamics modulate water cycling and mortality risk in droughted tropical forest

Stand dynamics modulate water cycling and mortality risk in droughted tropical forest
Patrick Meir, Yann Salmon, Antonio C. L. Costa, Steel S. Vasconcelos, Alex A. R. Oliveira, Rafael S. Oliveira, Lucy Rowland, Maurizio Mencuccini, Oliver J. Binks, João A. S. Junior, Leandro V. Ferreira, Rafael Poyatos
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. Transpiration from the Amazon rainforest is 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 competitive release and increased growth rates. Consequently, the amount of water supplied as rainfall and directly recycled as transpiration increased to 100%, 25% greater than in adjacent non-droughted 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 even more prone to increased tree mortality.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/gcb.13851

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