Low phosphorus supply constrains plant responses to elevated CO₂ : A meta-analysis

Area of Science:

• Plant Physiology and Ecology
• Global Change Biology
• Nutrient Cycling

Background:

• Phosphorus (P) is vital for plant growth, and its low availability may limit responses to rising atmospheric carbon dioxide (eCO2).
• The extent to which P limitation affects plant adaptation to eCO2 remains debated.
• Understanding these interactions is crucial for predicting ecosystem productivity under future climate scenarios.

Purpose of the Study:

• To conduct a meta-analysis on the impact of phosphorus (P) limitation on plant growth, physiology, and morphology under elevated carbon dioxide (eCO2).
• To quantify how P availability influences plant responses to eCO2 across different species and experimental conditions.
• To identify data gaps and inform future research directions for global change impact assessments.

Main Methods:

• Meta-analysis of experimental data manipulating both CO2 and P levels in young woody and non-woody plants.
• Analysis of plant photosynthetic rates, biomass allocation (aboveground, belowground, total), tissue nutrient concentrations, leaf area, and root length.
• Comparison of responses between high and low P availability conditions and across different plant functional types.

Main Results:

• Low P availability attenuated plant photosynthetic response to eCO2 by approximately 25%, resulting in reduced, though still positive, gains compared to high P conditions.
• Low P limited eCO2-induced increases in aboveground, belowground, and total biomass by 14.7%, 14.3%, and 12.4%, respectively, effectively halving the response seen under high P.
• Low P did not significantly alter eCO2 effects on tissue nutrient concentration, suggesting nutrient flexibility, but reduced eCO2-induced leaf area expansion (14.3%) while not affecting root length.

Conclusions:

• Phosphorus limitation significantly constrains plant growth and physiological responses to elevated CO2, highlighting its critical role in mediating climate change impacts.
• Plant tissue nutrient flexibility is a key mechanism enabling biomass responses to eCO2 under P-limited conditions.
• Further long-term, field-based experiments manipulating both CO2 and P are essential for ecosystem-scale understanding and improved global change modeling.