内蒙古克氏针茅草原生态系统-大气通量交换特征

基于内蒙古克氏针茅草原生态系统的涡动相关观测资料和小气候梯度系统观测资料，对研究区碳通量和水热通量的日、季动态进行了研究.结果表明：克氏针茅草原生态系统生长季的碳通量日动态呈U型曲线，即日出前释放CO₂，日出后开始吸收CO₂，正午前后达峰值，午后吸收CO₂减弱，日落后重新转为释放CO₂；9月白天CO₂吸收最为强烈，8月次之，10月最低.克氏针茅草原的感热和潜热通量的日动态均呈倒U型曲线，与碳通量日动态相反，即白天感热和潜热通量多为正值，夜间感热为负值，潜热接近于零；感热通量以5月最高，潜热通量以9月最高.冬季草地为弱碳源，CO₂通量较小，夏季表现为明显的碳汇.

Characteristics of net ecosystem flux exchanges over Stipa krylovii steppe in Inner Mongolia

Based on an entire year continuous measurement of surface fluxes by eddy covariance (EC) tower and micro-climate gradient observation system, the diurnal and seasonal dynamics of net ecosystem fluxes including carbon, water, and heat fluxes over Stipa krylovii steppe in Inner Mongolia were investigated. The results indicated that the diurnal pattern of carbon fluxes during growing season could be expressed as U curve. S. krylovii steppe ecosystem emitted CO2 before the sunrise and absorbed CO2 after the sunrise, with the maximum CO2 uptake around noon. The ecosystem had weaker CO2 uptake after the noon, and turned to emit CO2 after sunset. The CO2 uptake by S. krylovii steppe ecosystem reached the maximum in September, followed in August, and got the minimum in October. The diurnal dynamic patterns of sensible heat flux (Hs) and latent heat flux (LE) could be expressed as inverse U curves. The Hs and LE over S. krylovii steppe ecosystem were positive during the daytime, while Hs was negative and LE was close to zero during the nighttime. The ecosystem had the highest Hs and LE in May and September, respectively. In winter, the steppe acted as a weak carbon source, with the CO2 flux being small; while in summer, it became an obvious carbon sink.