Elevated CO₂ and temperature increase soil C losses from a soybean-maize ecosystem.

Area of Science:

• Agricultural Science
• Soil Science
• Ecology

Background:

• Soil carbon storage is crucial for climate regulation, but its response to environmental changes like warming and elevated CO2 is uncertain.
• Agroecosystems are significant contributors to global carbon cycling.
• Understanding soil carbon dynamics under climate change is vital for sustainable agriculture.

Purpose of the Study:

• To investigate the combined effects of elevated temperature and carbon dioxide (CO2) on soil carbon storage in a maize-soybean agroecosystem.
• To quantify changes in soil respiration and carbon pools under simulated climate change conditions.
• To evaluate the predictive accuracy of ecosystem models for soil carbon responses.

Main Methods:

• Field experiment with elevated temperature and CO2 enrichment over three years.
• Measurement of root and microbial respiration.
• Application of the DayCent process-based ecosystem model for decadal simulations.

Main Results:

• Both elevated temperature and CO2 increased microbial respiration by approximately 20%.
• Elevated temperature reduced root and rhizosphere respiration by approximately 25%.
• Total soil carbon and particulate organic matter declined, particularly under elevated CO2, suggesting a priming effect.

Conclusions:

• Combined warming and elevated CO2 are predicted to cause long-term declines in agricultural soil carbon.
• Empirical data indicate soil carbon loss, contrasting with some model predictions of carbon gain.
• Further research is needed to refine models and understand the mechanisms driving soil carbon loss.