干旱年份沙质草地生态系统净CO_2通量年变化特征

Characteristics of annual variation in net carbon dioxide flux in a sandy grassland ecosystem during dry years

草地生态系统是干旱半干旱区生态系统类型的重要组成部分,在区域生态系统碳平衡中起着极为重要的作用。采用涡度相关法对科尔沁沙质草地生态系统进行连续两年(2015和2016年)的碳通量观测,此两年恰逢研究区的相对干旱之年,年降水量约为历史平均值的60%。研究结果表明:1)年最大日均CO2吸收速率分别为-6.68和-9.58g·m^(-2)·d-1,年最大日均释放速率分别为5.69和5.21g·m^(-2)·d-1。2)生长季(5-9月)碳吸收量分别为-120.54和-139.83g·m^(-2),非生长季碳释放量分别为230.33和212.82g·m^(-2)。3)全年尺度上沙质草地生态系统表现为碳源,2015年净碳释放量(109.79g·m^(-2)·年-1)稍高于2016年(72.99g·m^(-2)·年-1)。4)生态系统净CO2交换量(NEE)与空气温度、土壤温度及土壤湿度存在显著相关关系,但不同年份同期NEE对环境温度和湿度的响应程度不尽一致。

Grassland ecosystems are a major component of terrestrial ecosystems in arid and semi-arid regions and play an important role in regional carbon balances.Continuous observation(from 2015 to 2016)of carbon dioxide flux was conducted using the eddy covariance technique in the‘Horqin Sandy Land'grassland ecosystem.The study period coincided with the drought in the study area and the annual rainfall during the study was60% of the historical average.Key results were:1)The maximum daily absorption rates were-6.68 and-9.58 g·m^(-2)·d-1,respectively,in 2015 and 2016,while the release rate was 5.69 and 5.21 g·m^(-2)·d-1.2)The amount of CO2 absorption was-120.54 and-139.83 g·m^(-2) during growing season and the emission was 230.33 and 212.82 g·m^(-2) during the non-growing season.3)The Horqin sandy grassland ecosystem was a carbon source when considered from an annual perspective.The net carbon release in 2015(109.79 g·m^(-2)·yr-1)was slightly greater than that in 2016(72.99 g·m^(-2)·yr-1).4)There were significant correlations between net ecosystem exchange(NEE)and air temperature,soil temperature,and soil moisture.However,the response of NEE to environmental temperature and humidity was not consistent across the two years.