喀纳斯保护区西伯利亚云杉树干液流动态变化

基于树干液流与树木蒸腾作用之间的关系,在新疆喀纳斯国家自然保护区内,采用TDP热扩散探针法连续监测了不同径级的西伯利亚云杉阳生面和阴生面的树干液流,明确不同大小的树体在参与森林水分循环中的的作用及其差异。结果表明:6—9月,西伯利亚云杉树干液流季节变化呈多峰曲线型,同一径级西伯利亚云杉树干阳生面与阴生面的液流启动时间、达到峰值时间一致; 8月份的树干液流量比其他月份的大,其大、小径级树干阳生面的最大液流速率分别是阴生面的1.45倍和1.19倍; 生长季内大径级西伯利亚云杉的总液流通量为5 974.90 kg,小径级的为1 628.71 kg; 晴天时树干液流的日变化呈多峰型,阴天时为单峰型; 夜晚时段小径级西伯利亚云杉的液流持续存在的时间较大径级的长,不同天气条件下的夜间液流主要用于树体自身夜间补水; 大径级和小径级西伯利亚云杉阳生面、阴生面的夜间液流速率分别是晴天的1.49、1.23倍和1.13、1.20倍。研究表明,影响西伯利亚云杉树干液流昼夜变化的主要因素为气温、水汽压、光合有效辐射、土壤温湿度和风速。

Dynamic changes of trunk sap flow of Picea obovata in the Kanas National Nature Reserve

Based on the relationship between sap flow and transpiration, the stem sap flow in different DBH(diameter at breast height)of Picea obovatas on both the sunny and the shady side were monitored using TDP(thermal dissipation method)constantly in the Kanas National Nature Reserve, northwest of Xinjiang. The purpose of this work was to evaluate role of tree size in forest hydrological cycle. The results showed that the changes of the stem sap flow of P. obovatas were multi-peak curves from June to September. Both the starting and peaking time of the stem sap flow of sunny side were consistent with that of the shady side in two DBH class of P. obovatas. The value of stem sap flow in August was highest, and the maximum flow rate in the sunny side of large and P. obovatas of small DBH were 1.45 and 1.19 times of that of shaded side, respectively. The total sap flow flux of P. obovatas of large DBH was 5 974.90 kg, and small one was 1 628.71 kg. On sunny days, the change of stem sap flow was multi-peak curve, but was unimodal type on cloudy days. The sap flow of P. obovatas of small DBH at night persisted longer time path than that large one. The sap flow at night was mainly used for replenishing water on sunny or cloudy days. The mean overnight flow rate of sunny side and shady side of P. obovatas of large DBH on cloudy day were 1.49 and 1.23 times of its on sunny day, and the P. obovatas of small DBH were 1.13 and 1.20 times, respectively. The main environmental factors affected stem sap flow were air temperature, vapor pressure, photosynthetically active radiation, soil temperature, soil humidity and wind speed.