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 the atmospheric boundary layer (ABL) and forest carbon metabolism, while those during the dormant season were controlled mainly by ABL. The seasonal dynamics of the [CO2] near the forest floor were determined mainly by soil respiration, while those above the canopy were jointly controlled by canopy photosynthesis and ecosystem respiration.
出处
《植物生态学报》
CAS
CSCD
北大核心
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
关键词
大气边界层
CO2源汇
垂直梯度
帽儿山
atmospheric boundary layer, CO2 source/sink, vertical gradient, Maoershan