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作 者 ：同小娟,张劲松*,孟平,尹昌君,高峻,黄辉,国琳

期 刊 ：生态学报 2009年 29卷 12期 页码：6638~6645

关键词：人工林；净生态系统碳交换；涡度相关；光合有效辐射；气温；饱和差；

Keywords:plantation, net ecosystem carbon exchange, eddy covariance, photosynthetically active radiation, air temperature, vapor pressure deficit,

摘 要 ：植树造林使我国森林碳储量显著增加，人工林潜在的碳汇功能不容忽视。基于涡度相关技术，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了连续2a的碳通量观测，以探讨净碳交换（NEE）与气象因子的关系。结果表明：在主要生长季（4~9月份），夜间日平均NEE（生态系统呼吸）随气温升高呈指数增长（P<0.01）。2006年和2007年生态系统呼吸的温度敏感系数（Q10）分别为1.92和1.86。气温在10℃以下时，NEE日总量较小。气温超过10℃后，人工林以净吸收大气CO2为主，且日吸收量随温度升高迅速增加。白天净碳吸收量随光合有效辐射（PAR）增加而增大（P<0.01），可由直角双曲线方程描述；不过，当饱和差（VPD）小于1.0 kPa时，二者呈线性相关（P<0.01）。2006年和2007年主要生长季（4~9月份）的平均表观初始光能利用率（α）分别为0.032和0.019，平均最大光合速率（Pmax）分别为0.96mg·m-2·s-1和1.10 mg·m-2·s-1。α和Pmax都存在季节变化。在月尺度，Pmax与VPD和PAR呈明显的负相关关系（分别为P<0.01和P<0.05），但与气温相关性不显著；α与对应的PAR、气温和VPD均无明显相关关系。

Abstract:In China, the potential carbon sink of plantation could not be neglected because forest carbon storage increased significantly by afforestation in recent decades. In this study, CO2 flux was measured continuously using the eddy covariance technique over a 30-year aged mixed plantation in the hilly zone of the North China from 2006 to 2007. The major tree species are Quercus variabilis, Robinia pseudoacacia and Platycladus orientalis. The relationships between net ecosystem carbon exchange（NEE）and main meteorological factors were investigated. The results showed that daily mean nighttime NEE increased exponentially with an increase of air temperature (P<0.01). The temperature sensitivity (Q10) of ecosystem respiration was 1.92 in 2006 and 1.86 in 2007. On daily scale, NEE varied within a small range of ±5 g?m-2?d-1 when air temperature was lower than 10℃. Daily net carbon uptake by plantation increased obviously with air temperature when air temperature was more than 10℃. In the main growing season (April-September), daytime net carbon uptake was positively related with photosynthetically active radiation (PAR). The relationship between NEE and PAR could be expressed by the rectangular hyperbolic function. However, there was a linear relationship between NEE and PAR when vapor pressure deficit (VPD) was less than 1.0 kPa. In the main growing season, the apparent initial light use efficiency (α) averaged 0.032 in 2006 and 0.019 in 2007. The maximal assimilation rate (Pmax) averaged 0.96 mg?m-2?s-1 in 2006 and 1.10 mg?m-2?s-1 in 2007. Seasonal variation of Pmax and α was obvious. On monthly scale, Pmax had negative correlations with VPD (P<0.01) and PAR (P<0.05) but was not related with air temperature. No significant correlation could be found between α and PAR, VPD and air temperature.

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