Towards a universal model for carbon dioxide uptake by plants.

Area of Science:

• Ecology
• Plant Physiology
• Climate Science

Background:

• Gross primary production (GPP) is crucial for the terrestrial carbon sink, yet Earth System Models (ESMs) struggle to accurately represent its response to environmental changes.
• Current models lack a robust theoretical framework for GPP, particularly regarding the regulation of leaf internal to external CO2 ratios (χ).

Discussion:

• This study introduces a novel approach by linking an evolutionary optimality hypothesis to the regulation of leaf CO2 ratios (χ).
• The derived quantitative dependencies of χ on temperature, vapor pressure deficit, and elevation align with empirical data from over 3,500 global leaf stable carbon isotope measurements.
• A single global equation successfully unifies existing models of photosynthesis and light-use efficiency.

Key Insights:

• A simple evolutionary optimality hypothesis accurately predicts leaf CO2 ratios (χ) across varying environmental conditions.
• The developed global equation provides a unified framework for modeling C3 photosynthesis and light-use efficiency.
• The model demonstrates broad applicability and successfully predicts GPP across diverse biomes and plant functional types.

Outlook:

• This research offers a theoretical foundation for understanding plant functional coordination and ecosystem emergent properties.
• The findings pave the way for reformulating GPP controls in next-generation Earth System Models.
• The unified equation presents a more robust and accurate method for predicting future terrestrial carbon sequestration.