Carbon Gain, Carbon Use, and Persistence: How Elevated CO₂ and Warming Reshape High-Elevation Plants

Area of Science:

• Ecology
• Plant Physiology
• Climate Change Science

Background:

• High-elevation plants have limited carbon economies due to cold temperatures, short growing seasons, and low CO2.
• Global change (elevated CO2, warming) is expected to increase carbon uptake in alpine systems.
• However, observed biomass gains and carbon sequestration in these systems are inconsistent.

Purpose of the Study:

• To propose a three-gate framework (carbon gain, carbon use, persistence) explaining alpine plant responses to global change.
• To synthesize evidence from experimental, observational, and modeling studies.
• To highlight the importance of persistence over productivity for alpine carbon stability.

Main Methods:

• Synthesis of experimental, observational, and modeling evidence.
• Analysis of plant physiological responses (photosynthesis, water-use efficiency).
• Evaluation of carbon allocation, nutrient limitations, and demographic processes.

Main Results:

• Elevated CO2 increases photosynthesis and water-use efficiency; moderate warming can boost early productivity.
• Carbon gain is limited by sink strength, nutrient availability, respiration, and rhizosphere priming.
• Excess carbon is allocated to storage and defense, not durable biomass.
• Demographic factors like phenology, recruitment, and mortality control long-term persistence.

Conclusions:

• Persistence, not just productivity, dictates alpine carbon stability under global change.
• Carbon allocation constraints and demographic processes must be integrated into ecosystem models.
• Accurate projections of mountain carbon-climate feedbacks require considering these limitations.