华北低丘山地人工混交林净生态系统碳交换的变化特征

Characteristics of Net Carbon Exchange over a Mixed Plantation in a Hilly Area of the North China

采用涡度相关技术对华北低丘山地30年生栓皮栎-刺槐-侧柏人工混交林生态系统进行连续2年的碳通量观测。结果表明:人工混交林净生态系统碳交换(NEE)的年际和季节变化都很明显,但日变化只在生长季(4—10月)才变得显著。2006和2007年人工混交林NEE的变化范围分别在-27.1～8.1和-24.4～9.8gCO2·m-2d-1,最大月平均CO2吸收量分别出现在5月和7月。生长季净碳吸收约占全年的96%。人工混交林是较强的碳汇,2006和2007年净碳吸收量分别为549.1和445.4gC·m-2a-1。春季干旱是2007年人工混交林净碳吸收显著下降的主要原因。

In recent years,forest areas in China increased largely thanks to afforestation.The plantation area accounts for 30% of the total forest areas of China.To understand the potential carbon sink of the plantation,CO2 flux was measured continuously from 2006 and 2007 using the eddy covariance technique in a 30-year-old mixed plantation（Quercus variabilis,Robinia pseudoacacia and Platycladus orientalis） in a hilly area of the North China.The results showed inter-annual and seasonal variations of net ecosystem carbon exchange（NEE） were obvious.However,the diurnal variation was only remarkable in the growing seasons（from April to October）.Daily NEE ranged from-27.1 to 8.1 g CO2·m-2 d-1 in 2006,and from-24.4 to 9.8 g CO2·m-2 d-1 in 2007.Monthly mean CO2 uptake peaked in May in 2006 and in July in 2007.The magnitude of CO2 uptake during the growing season accounted for about 96% of the whole year.Annual net carbon uptake in the plantation was 549.1 g C·m-2 a-1 in 2006 and 445.4 g C·m-2 a-1 in 2007.Carbon sink in the mixed plantation was notable and its inter-annual variation was significant.Drought in spring of 2007 was the main reason that led to a significant decrease in net carbon uptake in the mixed plantation.