鼎湖山针阔叶混交林CO2浓度及通量变化特征

Characteristics of CO2 flux and concentration in coniferous and broad-leaved mixed forest in Dinghu Mountain

关键词:  针阔叶混交林, CO₂通量, 涡度相关法, 鼎湖山

Key words:  coniferous and broad-leaved mixed forest, CO₂ flux, eddy covariance method, Dinghu Mountain

摘要:

该研究采用珠三角典型森林植被生态系统的鼎湖山南亚热带常绿阔叶林通量观测站2012年CO₂通量资料和气象资料,分析了CO₂通量、净生态系统CO₂交换量及CO₂浓度的变化特征,及其与气象因子的关系。结果表明:(1)CO₂浓度日变化呈“一峰一谷”变化形态,在夜间或日出前后出现最大值,在午后到达最小值; CO₂通量日变化呈“单谷”曲线,在白天中午前后到达最小值(负值),夜间和早晨较高(正值)。(2)CO₂通量季节平均值的高低依次为春季>夏季>冬季>秋季,CO₂浓度季节平均值的高低次序则为冬季>春季>秋季>夏季,即非生长季高于生长季节,这可能与植物物候的季节变化所引起的 CO₂源汇强度改变有关。(3)2012年鼎湖山森林生态系统的CO₂年均浓度为664.7 mg·m^-3,CO₂通量年均值为-0.079 mg·m^-2·s^-1,NEE为-611 g C·m^-2·a^-1,表明鼎湖山针阔叶混交林近年来处于快速生长过程中,具有较强的碳汇功能。(4)CO₂通量及浓度与气温、饱和水气压差均成显著负相关关系,其中CO₂浓度与气温的相关性最高,其次为饱和水汽压差,表明气温和饱和水汽压差是影响CO₂浓度和通量的关键气象因子。受人类活动及气候变化的影响,近年来鼎湖山森林生态系统的碳汇功能有所增强。

Abstract:

We analyzed the variation characteristics of the CO₂ flux, net ecosystem CO₂ exchange(NEE), CO₂ concentration and the relationship with meteorological variables on the basis of the CO₂ flux data and meteorological data of the southern subtropical evergreen broad-leaved forest flux observation station of Dinghu Mountain, a typical forest vegetation ecosystem in the Pearl River Delta. The research results were as follows:(1)The diurnal variation of CO₂ concentration appeared to be in the form of “peak-valley”. Specifically, the CO₂ concentration variation was nearly at its peak at night or around sunrise. And the CO₂ concentration variation was nearly at its valley in the afternoon; Diurnal variation of CO₂ flux generally appeared to be a “valley” curve, approaching minimum value(negative)around noon and reaching maximum(positive)in the morning and at night.(2)The seasonal average of CO₂ flux could be shown as the following order: spring> summer> winter> autumn. The order of the seasonal average of CO₂ concentration could be shown as the following order: winter> spring> autumn> summer, from which we could find that the non-growth season was higher than the growth season in that it was related to the seasonal variation of CO₂ source/sink intensity caused by the seasonal variation of plant phenology.(3)In 2012, the average annual concentration of CO₂ in Dinghushan forest ecosystem was 664.7 mg·m^-3. The annual mean value of CO₂ flux was -0.079 mg·m^-2·s^-1, and net ecosystem CO₂ exchange capacity(NEE)was -611 g C·m^-2·a^-1, which indicates that mixed confer-broadleaf forest at the Dinghu Mountain has strong carbon sink function in rapid growth during recent years.(4)CO₂ flux and CO₂ concentration had a significantly negative correlation with the temperature and the pressure difference of saturated water, of which the correlation between CO₂ concentration and the temperature was the highest, and the second was the saturated vapor pressure difference, which indicates that the temperature and saturated vapor pressure difference are the key meteorological factors that affect CO₂ flux and CO₂ concentration. We found that carbon sink function of Dinghu Mountain forest ecosystem had been enhanced in recent years, which could be influenced by human activities and climate change.