Canopy functional trait variation across Earth's tropical forests.

Area of Science:

• Ecology
• Biogeography
• Remote Sensing

Background:

• Tropical forest canopies are critical interfaces for global carbon, water, and energy cycles.
• Current Earth System Models oversimplify tropical forests, lacking representation of their functional heterogeneity.
• Geographical variation in tropical forest canopy functional properties is poorly understood.

Purpose of the Study:

• To predict and map the functional diversity of tropical forests globally.
• To understand the geographical variation in tree functional traits across tropical regions.
• To identify areas for future data collection to improve global tropical forest models.

Main Methods:

• Combined field data from over 1,800 vegetation plots and tree traits with satellite remote-sensing, terrain, climate, and soil data.
• Predicted variation in 13 morphological, structural, and chemical functional traits of trees.
• Computed and mapped the functional diversity of tropical forests.

Main Results:

• Tropical American, African, and Asian forests occupy distinct functional trait spaces.
• Tropical American forests exhibit 40% greater functional richness compared to African and Asian forests.
• African forests show the highest functional divergence, exceeding American and Asian forests by 32% and 7%, respectively.

Conclusions:

• Geographical variation in tropical forest functional traits is substantial and predictable.
• Distinct functional trait spaces highlight regional differences in tropical forest ecosystems.
• The study provides a foundation for improved Earth System Model parameterization and identifies key areas for future research.