Nature study finds tropical trees adapt drought resistance across Puerto Rico rainfall gradient
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A study published in Nature analyzed 11 hydraulic traits from 290 trees of 18 species across Puerto Rico’s rainfall gradient of 1,000 to 4,000 mm per year. It found substantial intraspecific variation in embolism resistance and stomatal safety margins, with trees in drier forests showing stronger drought resistance. The results challenge assumptions from temperate studies that within-species hydraulic variation is limited.
The Rainfall Gradient
The study collected 11 hydraulic traits from 290 trees representing 18 species along Puerto Rico’s fourfold rainfall gradient, from 1,000 mm to 4,000 mm per year. Embolism resistance and stomatal safety margins were among the traits measured. Species turnover accompanied the within-species changes, according to the paper in Nature. The gradient provided a natural laboratory for comparing wet and dry tropical forest responses.
Intraspecific Hydraulic Trait Variation
Most species exhibited more embolism resistance and wider stomatal safety margins in drier forests than conspecifics in wetter areas. The authors found substantial within-species variation in hydraulic traits, contrasting with temperate-region studies that reported little variation. This indicates a mechanism for tropical trees to adapt to drier conditions without relying solely on species replacement. Species lacking such trait variability may be highly vulnerable if droughts intensify.
Implications for Predictive Models
The study’s authors write that incorporating both interspecific and intraspecific trait variation will advance forecasts of forest resilience to intensifying droughts. Current models that rely on interspecific variation alone may not capture the adaptability observed in Puerto Rico. Phys.org reported the findings challenge assumptions of limited within-species adaptive potential.
What's Next
Follow-up studies may test whether the Puerto Rico rainfall-gradient pattern holds in Amazonian, Congolese, and Southeast Asian tropical forests. It remains unclear how quickly species with low trait variability will decline if droughts become more frequent and severe.
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Nature study finds tropical trees adapt drought resistance across Puerto Rico rainfall gradient
