Elevated CO₂ interacts with nutrient inputs to restructure plant communities in phosphorus-limited grasslands

Area of Science:

• Ecology
• Plant Community Dynamics
• Global Change Biology

Background:

• Atmospheric CO2 and nitrogen (N) deposition are increasing globally, impacting plant communities.
• Interactions between rising CO2, N deposition, and phosphorus (P) limitation on plant communities are poorly understood.
• Previous research focused on N enrichment, with less attention to combined effects with CO2 and P limitation.

Purpose of the Study:

• To investigate the effects of simultaneous elevated CO2 (eCO2), N, and P additions on grassland biodiversity and community composition.
• To understand how these factors interact in P-limited grassland ecosystems.
• To compare responses between limestone and acidic grassland types.

Main Methods:

• Soil-turf monoliths from long-term N-addition (25+ years) and P-addition (11-25 years) sites were used.
• Monoliths were exposed to elevated CO2 (600 ppm) for three years.
• Nutrient additions (N and P) were applied alongside elevated CO2 treatments.

Main Results:

• Elevated CO2, N, and P additions significantly altered community composition in both grassland types.
• Limestone grasslands exhibited greater responsiveness to eCO2, with significant functional shifts driven by eCO2-nutrient interactions.
• Legume cover increased, and functional dominance shifted from grasses to sedges in response to combined eCO2 and nutrient treatments in limestone grasslands.

Conclusions:

• Elevated CO2 can disproportionately benefit P acquisition by certain species (e.g., sedges) in P-limited grasslands.
• Grassland functional composition is sensitive to eCO2 and nutrient loading, particularly in P-limited systems with diverse P-acquisition strategies.
• Acidic grasslands showed less sensitivity to eCO2 and nutrient interactions compared to limestone grasslands, possibly due to lower initial diversity and P-acquisition strategies.