New research reveals how efficiently Southeast Asian dipterocarps transport water, and towering trees more than 200 feet tall may not be as vulnerable to drought as scientists thought
For decades, scientists have argued that the tallest trees face one of nature’s toughest challenges: Transports water from roots to leaves hundreds of feet above the ground. Now, a study of towering trees in Southeast Asia shows that some of the world’s tallest flowering plants have evolved specialized systems to overcome this problem.Researchers studying dipterocarps in Malaysia have found that these giant rainforest trees have developed ways to efficiently transport water through their trunks, allowing them to cope with extremely high physical demands. The findings challenge the long-held belief that taller trees are more susceptible to drought.The research is published in the journal science On July 2, the focus was on 5 species of Dipterocarpaceae plants in the Kabili-Sepilok Forest Reserve on the island of Borneo. Scientists say the discovery could impact understanding of forests in a changing climate, as the top 1% of trees contain more than half of the carbon in aboveground parts of forests.“These trees are both rare and important, and existing projections suggest that weaker hydraulic systems put them at higher risk of dying from drought,” Paulo Bittencourt, a forest ecologist at Cardiff University in Wales and the study’s lead author, said in a statement.They added: “This prediction is included in some climate change impact models, and our study suggests this may not be correct. More research is now needed to investigate the hydraulic systems and drought resistance of other tall trees.”
Study trees taller than 20 stories
The research team spent three months in 2022 collecting samples from 38 dipterocarp trees, ranging from about 25 feet to 233 feet tall. The work involves collecting branch, leaf and trunk samples from trees as high as 20 to 30 stories tall.Samples had to be collected from the upper parts of the trees, so the scientists worked with trained climbers who climbed huge trunks to reach branches well above the forest floor.“These people can thread a rope through a tree as high as a 20- to 30-story building in the middle of the forest, climb up the tree and collect branches,” Bittencourt said in a separate statement.They added: “Some collections must be carried out at night when there is no sunlight. It’s more than just knowing how to string a rope and staying fit. You have to check for wasp nests, know if the branches are suitable, if the wood is sturdy – it’s no small thing. “The collected material was analyzed to understand characteristics related to water movement within the trees. The scientists examined the structure of xylem, the plant tissue responsible for transporting water and nutrients from roots to leaves.
Tall trees adjust internal pipes
The researchers found that taller Dipterocarpaceae plants have wider xylem vessels near the base of their trunks. These wider channels help reduce drag as the water moves upward against gravity.The leaves that grow near the tops of these trees also exhibit the ability to tolerate dry conditions without losing their function. Together, these adaptations allow trees to maintain water transport despite their great height.The findings do not mean that all tall trees are immune to drought. Different species have different biological systems and face different environmental pressures. But research suggests height alone may not determine whether a tree survives dry conditions.To study how these trees responded to water stress, the researchers also measured trunk growth before, during and after the 2023-2024 El Niño-related drought. They found that taller trees did not show greater growth declines during drought compared to shorter trees.
World’s tallest trees face similar challenges
These results add to the understanding that tree size and drought survival are more complex than previously thought.Adrian Das, a forest ecologist with the U.S. Geological Survey who was not involved in the study, said the findings are consistent with patterns seen during droughts in the Sierra Nevada. “The relationship between body size and mortality during drought varies across species,” he explained to Mona Patterson of Science .In these forests, factors such as susceptibility to bark beetle damage appear to have a greater impact on tree mortality than height alone.The study also provides a different perspective on how trees respond to their surroundings. The findings prompt us to rethink the nature of trees, Julieta Rosell, a functional ecologist at the National Autonomous University of Mexico who was not involved in the study, told Science News’ Fechi Inyama.“They’re always doing things, they’re always changing their body structure,” she told the outlet. “This gives the trees a different perspective because they look peaceful.”
Giant trees around the world reveal different survival strategies
Research on Southeast Asia’s Dipterocarpaceae family complements research on other giant tree species that have developed their own ways of surviving extreme conditions.The General Sherman Tree in California’s Sequoia National Park is the largest known living single-stem tree in the world. This giant sequoia is approximately 83.8 meters tall and its trunk volume is estimated to be 1,487 cubic meters. Although it is not the tallest tree on Earth, its massive size makes it one of the most studied trees in the world.The General Sherman Tree’s age is estimated to be between 2,200 and 2,700 years old, in part due to the giant sequoia’s thick, fire-resistant bark. The bark thickness of old trees can exceed 90 cm. Fire can also help these forests by releasing seeds from the cones and reducing competing vegetation.
Largest Living Tree: General Sherman Giant Sequoia
The tallest tree known today belongs to another species: coast redwood. These trees grow in coastal areas of northern California and southern Oregon, and their height far exceeds that of most other plants.The tallest known living tree is Hyperion, a coastal redwood discovered in 2006 in Sequoia National and State Parks. It is approximately 115.9 meters tall, but its exact location is kept secret to prevent damage from too many visitors.Coast redwoods benefit from the cool, moist conditions near the Pacific Ocean. Coastal fogs provide extra moisture during dry periods, while their biological adaptations help them transport moisture through tree trunks that can rise more than 100 meters into the air.Some historical giants, such as the Daleville Giant, also belong to the Coast Redwood species. Before it fell in 1991, the tree was approximately 113 meters tall.Another tree that can reach extremely high heights is the Australian mountain ash. Some past specimens grew to over 100 meters, although no living mountain ash reaches the height of the tallest coast redwoods.Scientists continue to study these giant trees as their survival provides clues to how forests may respond to future climate stresses. New dipterocarp research shows that some of the tallest trees on Earth may have more control over their water systems than scientists once thought.
