中文摘要：

以科尔沁沙质草地为研究对象,利用开路涡度相关系统和LI-8150土壤呼吸自动观测系统,分析了生长季生态系统二氧化碳（CO2）净交换量（NEE）的变化特征,土壤呼吸（Rs）对生态系统呼吸（R（eco））的贡献率,以及生态系统总初级生产力（GPP）的大小。结果表明：生长季NEE存在明显的月均日变化特征,总体呈单峰型,其中7月的日变化最为明显,NEE月均日最大吸收速率（-5.62μmol·m^-2·s^-1）和最大释放速率（3.14μmol·m^-2·s^-1）均出现在7月份;生长季内生态系统总体表现为碳汇,固碳量为25.85 g C·m^-2;Rs对R（eco）的贡献率为78.39%,R（eco）对GPP的贡献率为90.62%,生长季内GPP总累积量为275.51g C·m^-2。

英文摘要：

Based on the eddy covariance system and LI-8150 automatic soil respiration observation system, this present study investigated the characteristics of net ecosystem CO2 exchange （NEE）, the contribution of soil respiration （Rs） to ecosystem respiration （Reco）, and the gross primary productivity （GPP） in Horqin sandy grassland of China. The results showed that the average monthly diurnal variations of NEE changed apparently with a single peak curve; the highest absorption rate （-5.62 μmol·m^-2·s^-1） and the highest release rate （3.14 μmol·m^-2·s^-1） were observed in July. The sandy grassland ecosystem was a carbon sink, with a sequestration amount of 25.85 g C·m^-2 during the growing season. The contribution of Rs to Reco accounted for 78.39%; the GPP was 275.51 g C·m^-2 and the contribution ofReco to GPP accounted for 90.62%.