Study Reveals How Southeast Asia's Giant Trees Resist Drought

Giant trees in Southeast Asia possess a remarkable resilience to drought, comparable to their shorter counterparts, according to a new international study with Spanish participation. These towering giants, some exceeding 70 meters in height, achieve this feat through sophisticated hydraulic adaptations that facilitate water transport to their highest reaches.

The research, published in the journal Science, focused on species like Kapur (Dryobalanops lanceolata) and White Seraya (Parashorea malaanonan), found in the tropical rainforests of Asia. Previously, the scientific community widely believed that taller trees were more susceptible to water scarcity due to the immense difficulty of pumping water from their roots to the uppermost branches.

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The secret of their resistance lies in the xylem, a circulatory system formed by microscopic conductors that, in these giants, widen as they descend from the crown to the base of the trunk to facilitate circulation.

Scientists discovered that the secret lies within the xylem, the tree's vascular system. In these giants, the xylem vessels widen as they descend from the canopy to the trunk's base, optimizing water circulation. Maurizio Mencuccini, a researcher at CREAF and the study's sole Spanish co-author, explained that the leaves also adapt by altering salt and sugar concentrations to retain more water, thereby extending photosynthesis.

To confirm these mechanisms, the research team monitored the growth of 38 trees across five different species in northern and northwestern Borneo for two years. They specifically assessed the trees' response to an extreme drought event during the El Niño climate phenomenon. The study's authors consider this finding to be "good news" because the tallest one percent of the world's trees store over half of the total carbon accumulated in tropical forest vegetation. The risk of these colossal trees dying from drought may be overestimated in current models, as their capacity to compensate for the effects of height had not been fully considered.

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The finding is 'good news,' as the 1% tallest trees in the world store more than half of all the carbon accumulated in tropical forest vegetation.