Mechanism and bio‐environmental controls of ecosystem respiration in a cropland in the North China plains

Abstract

CO₂ flux was measured continuously using the eddy covariance technique in a wheat‐maize rotation system in the North China Plains from October 2002 to October 2006. The annual and seasonal variation of ecosystem respiration and the bio‐environmental controls on them were investigated. The results show that ecosystem respiration (R_ec) in the cropland increased exponentially with soil temperature at 5 cm depth. The temperature sensitivity coefficient (Q₁₀) for ecosystem respiration varied from 3.5 to 5.4 for wheat and from 2.4 to 4.5 for maize. In the wheat growing season, monthly average R₀ (ecosystem respiration at 0°C) increased linearly with soil temperature and logarithmically with leaf area index (LAI). Monthly average Q₁₀ decreased logarithmically with R ₀. Residual R _ec was significantly correlated with LAI. After considering LAI, the modified Q₁₀ model could estimate R _ec better than before. The simulation results show that annual ecosystem respiration in the wheat‐maize rotation system in the North China Plains was 1327, 1348, 1040 and 1171 gC m^‐2 yr^‐1 for the 4 years of the study. As a 4‐year average, seasonal mean ecosystem respiration in wheat (2.60 gC m^‐2 day^‐1) was much lower than in maize (6.09 gC m^‐2 day^‐1). However, integrated ecosystem respiration for the wheat growing season (566 gC m^‐2) was slightly higher than that for maize (520 gC m^‐2). These account for 46.4 and 42.6% of the annual values, respectively.

Keywords:

• ecosystem respiration
• Q₁₀
• eddy covariance
• LAI
• soil temperature
• wheat‐maize rotation system