Estimation of soil respiration in a paddy ecosystem in the subtropical resion of China

Water vapor, energy exchange, and CO2 flux were measured continuously from 2003 to 2005 using the eddy covariance technique in a paddy ecosystem in the subtropical region of China. The CO2 fluxes at nighttime during fallow periods （from middle October to late April） were used to analyze the dynamics of soil respiration and its relationship with soil temperature, and to simulate the annual dynamics of soil respiration in paddy ecosystems. The variation of soil respiration showed a clear seasonal pattern. The soil respiration rates at night during the fallow periods were 52--398 mg· m^-2· h^-1, and exponentially correlated （P〈0.001） with soil temperatures at different depths of soil （5, 10, and 20 cm）, particularly the temperature measured at a depth of 5 cm. Based on the simulated exponential equations developed, annual average soil respiration rates and total soil respiration of paddy soil in the subtropical region of China were estimated to be 178.5--259.9 mg· m^-2· h^-1 and 1.56--2.28 kg· m^-2· a^-1, respectively. The simulation equations can be applied to evaluating soil respiration in paddy ecosystems during the rice-growing season.

Estimation of soil respiration in a paddy ecosystem in the subtropical region of China

Water vapor, energy exchange, and CO₂ flux were measured continuously from 2003 to 2005 using the eddy covariance technique in a paddy ecosystem in the subtropical region of China. The CO₂ fluxes at nighttime during fallow periods (from middle October to late April) were used to analyze the dynamics of soil respiration and its relationship with soil temperature, and to simulate the annual dynamics of soil respiration in paddy ecosystems. The variation of soil respiration showed a clear seasonal pattern. The soil respiration rates at night during the fallow periods were 52–398 mg·m⁻²·h⁻¹, and exponentially correlated (P<0.001) with soil temperatures at different depths of soil (5, 10, and 20 cm), particularly the temperature measured at a depth of 5 cm. Based on the simulated exponential equations developed, annual average soil respiration rates and total soil respiration of paddy soil in the subtropical region of China were estimated to be 178.5–259.9 mg·m⁻²·h⁻¹ and 1.56–2.28 kg·m⁻²·a⁻¹, respectively. The simulation equations can be applied to evaluating soil respiration in paddy ecosystems during the rice-growing season. Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Nos. KZCX2-YW-423 and KZCX2-YW-432-1), the project of Asia-Pacific Environmental Innovation Strategy (APEIS), and the National Basic Research Program of China (Grant Nos. 2002CB412503 and 2005CB121106)