Using CO2 flux data of winter wheat recorded by eddy covariance system, combined with the meteorological data, we examined the diurnal variations of CO2 fluxes in four growth stages (tillering stage, overwintering stage, jointing stage and filling stage) of winter wheat in an agroecosystem of the North China Plain from 2013 to 2014. The seasonal variation of net ecosystem exchange and its relationship with meteorological factors were investigated. The results showed that the net ecosystem exchange in the whole growing season was -360.15 g C·m-2. The gross primary productivity in the whole growing season was 1920.01 g C·m-2. The winter wheat agroecosystem had strong capacity in carbon sequestration. The CO2 fluxes showed an obvious diurnal and seasonal variation characteristics in winter wheat agroecosystem. This ecosystem was a carbon source in tillering stage, while it was a carbon sink in overwintering stage, jointing stage and filling stage. The mean value of apparent initial light energy utilization was 0.03 mg CO2·μmol-1. The mean value of ecosystem production was 1.53 mg CO2·m-2·s-1 when light was saturated. The monthly average value of ecosystem respiration was 193.92 g C·m-2·month-1. The net ecosystem exchange and photosynthetically active radiation had a significant correlation in four growth stages of winter wheat. The correlations between net ecosystem exchange and vapor pressure deficit were significant in all the growth stages. There was a positive correlation between daily total net ecosystem exchange and soil temperature in tillering stage, overwintering stage and filling stage, but a negative correlation between them in jointing stage.
利用2014—2015年中国科学院封丘农业生态实验站涡度相关系统观测的冬小麦农田生态系统CO2通量数据,结合试验地常规气象观测系统的气象数据,分析冬小麦4个生育期(分蘖期、越冬期、拔节期和灌浆期)内CO2通量的日变化,研究净生态系统碳交换(NEE)的季节变化及其与气象要素的关系.结果表明: 冬小麦整个生育期内NEE为-360.15 g C·m-2,总初级生产力总量为1920.01 g C·m-2,冬小麦农田生态系统具有较强的固碳能力.冬小麦农田生态系统CO2通量具有明显的日变化和季节变化特征,分蘖期表现为碳源,越冬期、拔节期和灌浆期表现为碳汇.表观初始光能利用率平均值为0.03 mg CO2·μmol-1,光饱和时的生态系统生产量平均值为1.53 mg CO2·m-2·s-1,月平均生态系统呼吸为193.92 g C·m-2·month-1.冬小麦农田生态系统4个生育期NEE与光合有效辐射的相关关系均达到极显著水平.分蘖期、拔节期和灌浆期NEE与饱和水汽压差的相关关系极显著,越冬期达显著水平.冬小麦分蘖期、越冬期和灌浆期NEE日总量与土壤温度呈正相关,拔节期呈负相关关系.
Keywords: carbon dioxide flux; eddy covariance system; net ecosystem exchange; the North China Plain; winter wheat agroecosystem.