Stronger Sensitivity of Plant Photosynthesis to Rising CO₂ in High Elevation Ecosystems

Area of Science:

• Ecology
• Plant Physiology
• Climate Change Science

Background:

• The CO2-fertilisation effect (CFE) is a key factor in the increasing land carbon sink.
• CFE is theoretically expected to rise with elevation, but this pattern is understudied.
• Understanding elevation-dependent CFE is crucial for accurate climate modeling.

Purpose of the Study:

• To investigate the elevation-dependent pattern of CFE on vegetation productivity.
• To quantify the impact of elevated CO2 on gross primary production (GPP) in alpine environments.
• To evaluate the performance of current terrestrial biosphere models in representing CFE.

Main Methods:

• Conducted a 6-year CO2 enrichment experiment (+100 ppm) in an alpine grassland.
• Analyzed the influence of water availability and biomass allocation on CFE seasonally.
• Synthesized data from 10 global CO2 enrichment experiments and utilized a satellite-based EC-LUE model.

Main Results:

• Elevated CO2 increased GPP by 25.5% ± 4.6% in the alpine experiment.
• CFE was found to increase with elevation across global experiments and satellite data.
• Satellite-derived CFE showed a positive elevation-dependent pattern, though weaker than experimental findings.

Conclusions:

• CFE exhibits a significant elevation-dependent pattern, increasing with altitude.
• Terrestrial biosphere models currently fail to capture this crucial elevation-dependent CFE.
• Improved model representation of plant physiological adaptation to rising CO2 at different elevations is needed.