稻田CO2通量对光强和温度变化的响应特征

Responses of CO_2 Fluxes to Light Intensity and Temperature in Rice Paddy Field

采用涡度相关法对我国亚热带稻田生态系统CO2通量进行了连续监测,并对CO2通量随光强和温度变化的响应特征进行了分析.结果表明,白天稻田生态系统CO2通量对光强的响应过程可以用直角双曲线方程进行描述.随光强的增加,CO2通量（绝对值）呈增加趋势,当光强大于1 000μmol/（m2.s）时,CO2通量变化比较稳定.早、晚稻间以及不同生育期水稻的光量子利用效率和最大光合速率存在一定的差异.晚稻的光量子利用效率（0.046 5-0.099 9μmol/μmol）高于早稻（0.017 6-0.054 1μmol/μmol）,并以水稻生长旺盛期的光量子利用效率和最大光合速率最高.夜间稻田生态系统呼吸速率随土壤温度的升高呈指数增加,5 cm土层温度可以作为反映稻田呼吸速率变化的温度指标.早稻生长季生态系统呼吸对温度的变化明显较晚稻生长季更为敏感.

CO2 fluxes in rice paddy ecosystem in subtropical hilly region were measured continuously using eddy covariance technique.The objectives were to investigate the responses of CO2 fluxes to light intensity and temperature in the paddy ecosystem.Results showed a rectangular hyperbolic light-response function could be used to describe the relationship of CO2 flux and photosynthetic photon flux density（PPFD）.The absolute values of CO2 fluxes increased with the increment of PPFD.When PPFD was higher than 1 000μmol/（m^2·s）,the maximum was observed.CO2 fluxes responded differently to light between early and late rice.Values of quantum yield of late rice（0.046 5-0.099 9μmol/μmol） were general higher than that of early rice（0.017 6-0.054 1μmol/μmol）.Moreover,the quantum yield and the maximum rate of photosynthesis assimilation in the blooming stage were higher than that in tillering and ripening stages.In nighttime,respiration from soil and plants（ecosystem respiration,Reco） changed exponentially with the increase of soil temperature at the depth of 5 cm（T5）,10 cm（T10）,and 20 cm （T20）,respectively.Whereas,T5 was more feasible than others to be considered as the temperature parameter for Reco calculation.During early rice growing season,Reco was more sensitive to temperature change than that during late rice growing season.