Differences in xylem and leaf hydraulic traits explain differences in drought tolerance among mature Amazon
Thomas L Powell1,2, James K Wheeler1,3, Alex A R de Oliveira4
1Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
Global Change Biology
|April 21, 2017
Summary
Drought-tolerant Amazon trees possess distinct xylem and leaf traits, unlike drought-intolerant species. These physiological differences are conserved across sites, crucial for predicting forest responses to climate change.
Area of Science:
- Ecology
- Plant Physiology
- Climate Change Science
Background:
- Amazon forests face uncertain impacts from climate change, particularly drought.
- Previous experiments showed varied tree mortality rates, suggesting species-specific drought tolerance.
- Understanding the physiological basis of this tolerance is key to predicting forest futures.
Purpose of the Study:
- To investigate the physiological traits (xylem pressure at 50% conductivity, leaf turgor loss point, cellular osmotic potential, cellular bulk modulus of elasticity) linked to differential drought tolerance in Amazonian tree species.
- To determine if these traits are conserved across different environmental conditions within the Amazon.
- To improve the representation of plant hydraulics in ecosystem models for better climate change impact predictions.
Main Methods:
- Measured key hydraulic traits on selected tree species across two large-scale drought experiments in the Brazilian Amazon.
- Classified species into four plant functional types (PFTs) based on drought tolerance (mortality rates) and successional status (wood density).
- Statistically compared trait values between PFTs and across experimental sites.
Main Results:
- Drought-intolerant species exhibited significantly higher water potentials for xylem pressure at 50% conductivity, leaf turgor loss point, and cellular osmotic potential compared to drought-tolerant species.
- No significant differences in these traits were found between early- and late-successional PFTs.
- Observed trait differences between drought-tolerant and intolerant PFTs were consistent across the two study sites, despite variations in soil and dry season length.
Conclusions:
- Xylem and leaf hydraulic traits are critical determinants of drought tolerance in Amazonian trees, largely independent of successional status.
- The spatial conservation of these traits suggests their fundamental role in species' drought response.
- This research enhances our understanding of plant hydraulics, vital for improving climate change impact models on tropical forests.
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