温带落叶阔叶林冠层CO_2浓度的时空变异  

Spatio-temporal variations of CO_2 concentration within the canopy in a temperate deciduous forest,Northeast China

作　　者：焦振[1] 王传宽[1] 王兴昌[1] 

机构地区：[1]东北林业大学生态研究中心,哈尔滨150040

出　　处：《植物生态学报》2011年第5期512-522,共11页Chinese Journal of Plant Ecology

基　　金："十二五"科技支撑项目(2011BAD37B01);林业公益性行业科研专项(200804001;201104009-05);国家自然科学基金(30625010)共同资助

摘　　要：为了研究温带落叶阔叶林CO2浓度(摩尔分数,[CO2])的时空变化特征,利用帽儿山通量塔8层[CO2]廓线系统分析了[CO2]的时间动态及垂直梯度,并结合森林小气候的同步测定数据探讨了影响[CO2]时空变化的因子。结果表明:帽儿山温带落叶阔叶林的[CO2]及其垂直梯度具有明显的日变化和季节变化。在日尺度上,[CO2]呈"单峰"曲线,在夜间或日出前后出现最大值,日出后迅速降低,在午后达到最低值,日落时分又开始迅速升高。在季节尺度上,生长季的[CO2]日变幅明显大于非生长季,且冬季(1、2和12月)白天呈"V"型,其他季节白天呈"U"型,这与白天对流边界层的持续时间随季节的变化趋势一致。在垂直方向上,[CO2]及其日变幅随高度增加而降低,并且在生长季夜间湍流交换较弱时其垂直梯度最显著;植被冠层的光合作用改变了生长旺季白天的[CO2]垂直格局,使冠层高度的[CO2]最低;休眠季节该垂直梯度大大减弱。近地层日均[CO2]与土壤温度的趋势相似,呈单峰曲线;而林冠上[CO2]在5月初和10月各出现一次峰值,最低值出现在8月初,与植被光合作用紧密相关。日尺度上[CO2]及其垂直梯度主要受控于大气边界层和生态系统碳代谢过程;年尺度上近地层[CO2]主要受控于土壤呼吸,而林冠上的[CO2]则受生态系统光合作用和呼吸作用的共同控制。Aims Although temperate broadleaved deciduous forest accounts for two-thirds of the forest area in northeastern China, its spatio-temporal variations of CO2 concentration （[CO2]） have not been quantified. Our objectives were to quantify diurnal and seasonal variations and vertical gradients of [CO2] and explore controlling factors. Methods A [CO2] flux tower with an 8-level [CO2] profile system （at 0.5, 2.0, 4.0, 8.0, 16.0, 20.0, 28.0 and 36.0 m） was installed at the Maoershan Forest Ecosystem Research Station in Heilongjiang Province （45°24＇ N, 127°40＇ E） in 2007. [CO2] at each level was measured with a LI-COR LI-840 infrared gas analyzer （IRGA） by drawing it from each level with a sample pump through tubes of equal length. The IRGA was controlled and data were collected with a datalogger. Automatic calibration was done for the IRGA once a day. A Vaisala GMP343 was installed at 36.0 m to monitor ambient [CO2] for quality control of the [CO2] profile data. We simultaneously measured micrometeorological variables, including wind speed, air temperature, relative humidity, photosynthetically active radiation, vapor pressure, soil temperature and water content. Important findings At a daily scale, maximum [CO2] occurred at night or sun rise, while the minimum occurred in the afternoon at all levels. This pattern was predominant in the summer. The diurnal course of the [CO2] was ＂V＂-shaped in winter but ＂U＂-shaped in other seasons. [CO2] decreased with increasing height, particularly on summer nights. During the daytime of summer, daily mean [CO2] within the canopy was substantially lower than the ambient [CO2], suggesting that the vegetation acted as a CO2 sink due to its photosynthesis. Daily mean [CO2] above the canopy peaked in spring and autumn and reached a minimum in summer, while that near the forest floor showed a unimodal seasonal pattern with its maximum in summer. The diurnal dynamics of [CO2] and their vertical gradients during the growing season were jointly controlled by th

关 键 词：大气边界层 CO2源汇 垂直梯度 帽儿山 

分 类 号：S715[农业科学—林学]