Quantifying and optimizing agroecosystem services in China's Taihu Lake Basin

Area of Science:

• Agricultural Science
• Environmental Science
• Ecosystem Services

Background:

• The Taihu Lake Basin, a major Chinese grain production area, suffers from severe water quality degradation.
• Rice-wheat agroecosystems are critical for food security but impact environmental quality.

Purpose of the Study:

• To analyze spatiotemporal changes in ecosystem services (grain yield, nitrogen loss, N2O emission, soil organic carbon accumulation) in the Taihu Lake Basin from 1986-2015.
• To evaluate the effects of straw return and fertilizer reduction strategies on ecosystem services.
• To propose pathways for stabilizing grain production and improving water quality.

Main Methods:

• Application of the Agricultural Production Systems Simulator (APSIM) at the county level.
• Simulation of six scenarios combining two straw return modes (full vs. none) and three fertilizer reduction levels (-5%, -10%, -20%).
• Analysis of ecosystem service trends and interrelationships.

Main Results:

• Annual grain yield and soil organic carbon (SOC) accumulation showed downward trends, while nitrogen (N) loss and N2O emissions increased from 1986-2015.
• Synergies were observed between increased grain yield and SOC accumulation (45.8% of land), and decreased N2O emission and N loss (2.4%).
• Trade-offs existed between increased SOC accumulation and decreased N loss (19.0%), and increased SOC accumulation and decreased N2O emission (2.4%).
• Fertilizer use positively correlated with grain yield and SOC, but reduced N loss and N2O emissions. Straw return increased yield and SOC, reduced N loss, but increased N2O emissions.

Conclusions:

• Targeted fertilizer reduction (20% where N application > 490 kg N/ha) and combined straw return with moderate fertilizer reduction (5% where N application is 380-490 kg N/ha) are recommended.
• These strategies aim to reduce nitrogen loss, stabilize grain supply, and mitigate water quality issues in the rice-wheat agroecosystems.
• Understanding ecosystem service dynamics is crucial for sustainable agricultural management in ecologically sensitive regions.