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Giant trees have no trouble pumping water to top branches
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- DeepHorus
New research reveals that the world's tallest tropical trees efficiently pump water to their topmost branches, challenging long-held scientific theory. A study led by the University of Exeter and Cardiff University, published in the journal Science, finds that adjustments to water transport inside giant Dipterocarp trees fully compensate for the challenges of drawing water upward. The findings upend conventional wisdom that height limits water transport, photosynthesis, and growth.
Conventional theory suggests that as trees grow taller, it becomes harder to transport water from roots to leaves due to vessel length and gravity, making trees more vulnerable to drought. This study, however, shows that Dipterocarp trees have evolved intricate adaptations that maintain water flow even under extreme low pressures. Professor Lucy Rowland of the University of Exeter explains that these vessels can keep water in liquid form despite the pressures required to reach heights over 80 meters.
Researchers examined Dipterocarp trees ranging from 7 to 71 meters tall in Malaysian Borneo, measuring traits at multiple positions along each tree. They found that taller trees compensate through water-carrying vessels that grow wider nearer the ground and leaves that withstand greater water stress before wilting. During the strong El Niño drought of 2023-2024, trunk growth rates showed no height-related loss compared to smaller trees.
The implications are significant for climate change models. The tallest 1% of trees store more than half of above-ground carbon in forests, yet existing predictions suggest their hydraulic systems place them at higher risk of drought-related death. Dr. Paulo Bittencourt, now at Cardiff University, says this study suggests that prediction may be incorrect, as tall Dipterocarps are hydraulically resilient.
Co-author Palasiah Jotan, a Malaysian PhD student, hopes these findings strengthen the case for protecting Dipterocarp forests under a changing climate. She notes that these trees dominate Borneo's rain forests and are central to regional ecology and biodiversity. The research team included the Sabah Forestry Department, UK Centre for Ecology & Hydrology, and institutions from several countries.
More research is now needed to investigate the hydraulic systems and drought resilience of other tall trees. This study was funded by the Natural Environment Research Council and is titled "Height does not impair the hydraulic system of the tallest tropical Dipterocarp trees." The findings challenge existing scientific theory and underscore the importance of protecting these towering giants in the face of climate change.
