Borneo study finds giant trees sidestep drought limits

giant trees – Researchers in Borneo report in Science that towering Dipterocarpaceae trees—some over 71 meters tall—show no height-related decline in drought-linked water transport. By measuring traits across 38 trees during an intense 2023 to 2024 drought, the team found t

In rainforests on Borneo. the tallest crowns rise far above the canopy—high enough that sampling them turns into a kind of race against the day. A team of researchers and professional climbers scaled giant Dipterocarp trees in Malaysia’s Kabili Sepilok Forest Reserve to take leaf. trunk. and branch samples from different heights.

The stakes were not just botanical. For decades, tree drought biology has leaned on a simple fear: the higher a tree’s water has to travel, the more gravity and resistance should hinder hydration—leaving the upper branches and leaves more vulnerable when rainfall drops.

But in results published July 2 in Science, that assumption hits a wall.

The study focused on water transport systems in a dominant tree family, the Dipterocarpaceae. From 38 trees spanning from 7.7 meters to 71 meters tall—over three-fourths as tall as the Statue of Liberty—the researchers measured 25 traits related to tree water transport. The tallest individual sampled was over 70 meters tall.

The work began with the physics the team wanted to test. Plant functional ecologist Arne Scheire. now at the Southeast Asia Rainforest Research Partnership in Kota Kinabalu. Malaysia. described how the path from roots to leaves becomes longer in taller trees. and how water traveling through a tree’s vessels. or xylem. encounters more resistance higher up. With gravity in the picture. that longer xylem should translate into a more stifled water potential—making it harder for water to be pulled upward as leaves release water.

Scheire and colleagues say no experiments had verified whether taller trees actually lose ground during drought under those pressures.

To probe that gap, the researchers climbed before dawn and sampled throughout the day. They also set up instruments before sunrise to measure the propensity for water to be sucked up into the trees at their most hydrated time of day.

Their findings point to compensations that appear to blunt the height problem. On average. taller trees started off with larger xylem widths at their base. a strategy the team says compensates for the increased resistance with height. Higher leaves, the researchers found, also adjusted their dehydration limit to accommodate less water being sucked to them.

That ability to recalibrate mattered during a real test. The team says the adaptations held during an intense drought lasting from 2023 to 2024. Crucially, they found no height-related declines in growth rate among their sampled trees—suggesting drought responses were independent of tree height.

The results also land in the middle of a debate that was already unsettling the old gravity-centric view. A competing theory had predicted that larger trees would develop adaptations like the ones measured in this study. Julieta Rosell. a functional ecologist at the National Autonomous University of Mexico in Mexico City who was not involved with the work. described the importance of the test for the field. She called it “neat” that the theory motivated the researchers to examine the uppermost parts of tall trees—something she said “was never done before.”.

For Scheire, the implications go beyond plant physiology. Big trees can store massive amounts of aboveground carbon. and they shape ecosystems by producing seeds and providing habitats for tropical organisms. Because this tree family is not showing greater susceptibility to drought. Scheire says it “may be a good long-term spot to sequester carbon” in Southeast Asia.

For Rosell, the report changes how trees should be imagined. Her focus is less on individual mechanisms and more on the portrait of the organism itself. She said the findings encourage a rethink about trees’ nature—that they are not just passive organisms standing in place. “They’re doing things all the time. making changes in their anatomy all the time. ” she said. adding that the new evidence gives “a different perspective to trees because they seem so quiet.”.

drought biology giant trees xylem Dipterocarpaceae Borneo rainforest water transport conservation carbon sequestration Science July 2