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 f...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 exponen- tially 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.展开更多
Carbon management index（ICM） is used to evaluate the scientificity of soil management.Soil organic carbon（SOC） and readily oxidized carbon （ROC） contents under Leucaena leucocephala stand, Acacia glauca stand,Ac...Carbon management index（ICM） is used to evaluate the scientificity of soil management.Soil organic carbon（SOC） and readily oxidized carbon （ROC） contents under Leucaena leucocephala stand, Acacia glauca stand,Acacia auriculiformis stand, Azadirachta indica stand,wasteland and dry cropland were determined and their ICM were calculated.The results showed that the SOC and ROC contents under the 6 land use types were 4.22-5.92 g·kg<sup>-1</sup> and 1.34-2.33 g·kg<sup>-1</sup>,respectively.No significant differences in SOC contents among these land uses were observed.The ROC contents under the 4 types of woodland,however,were significantly higher than these under dry cropland or wasteland（P【0.05）. The ROC were high significantly（P【0.001） correlated（R<sup>2</sup> is 66.3%） with SOC.Compared with wasteland,the ICM ranged from 1.77 to 2.36 under these woodlands,and 0.99 under dry cropland.It is revealed that the litter quantity and land management under these land uses may be the key factors resulting in the variation of ROC.At ecological fragile region of Dry-hot Valley,closure management is useful to sequestrate C in woodland soils.However,the management systems for soil carbon pool under dry cropland are not in a sound way.展开更多
基金the Knowledge Innovation Program of the Chinese Academy of Sci-ences (Grant Nos. KZCX2-YW-423 and KZCX2-YW-432-1)the project of Asia-Pacific Environmental Innovation Strategy (APEIS)the National Basic Research Program of China (Grant Nos. 2002CB412503 and 2005CB121106)
文摘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 exponen- tially 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.
文摘Carbon management index（ICM） is used to evaluate the scientificity of soil management.Soil organic carbon（SOC） and readily oxidized carbon （ROC） contents under Leucaena leucocephala stand, Acacia glauca stand,Acacia auriculiformis stand, Azadirachta indica stand,wasteland and dry cropland were determined and their ICM were calculated.The results showed that the SOC and ROC contents under the 6 land use types were 4.22-5.92 g·kg<sup>-1</sup> and 1.34-2.33 g·kg<sup>-1</sup>,respectively.No significant differences in SOC contents among these land uses were observed.The ROC contents under the 4 types of woodland,however,were significantly higher than these under dry cropland or wasteland（P【0.05）. The ROC were high significantly（P【0.001） correlated（R<sup>2</sup> is 66.3%） with SOC.Compared with wasteland,the ICM ranged from 1.77 to 2.36 under these woodlands,and 0.99 under dry cropland.It is revealed that the litter quantity and land management under these land uses may be the key factors resulting in the variation of ROC.At ecological fragile region of Dry-hot Valley,closure management is useful to sequestrate C in woodland soils.However,the management systems for soil carbon pool under dry cropland are not in a sound way.
