元宝枫树干液流的时空变异性研究

该研究应用热扩散式边材茎流计,对北京植物园绿地中元宝枫树干液流的时空变异特征进行了观测.研究结果显示:树干液流的日变化和季节差异与太阳辐射日变化和季节差异具有较好的一致性,夏季太阳升起比春秋早,落日比春秋晚,相应地树干液流启动夏季比春秋季早,进入低谷比春秋季晚;元宝枫为春季耗水性树种,树干平均液流速率春季0·00188cm/s、夏季0·00112cm/s、秋季0·00086cm/s;元宝枫树干液流存在明显的方位差异,同一样木,液流最大方位的流速可达平均值的122·1%,最小为平均值的86·3%,在同一株样木上,液流的方位差异较为稳定,不同样木液流最大和最小的方位不同,树干液流的方位差异与冠幅大小无关;在垂直高度上,春夏两季上部液流的波动节律明显早于下部和中部,液流速率上部最大,中部次之,下部最小.

Temporal and spacial variations of stem sap flow of Acer truncatum Bunge

The thermal dissipation sap flow probe (TDP) was applied to study the stem sap flow of Acer truncatum Bunge in Beijing Botanical Garden in 2005. Results showed that the daily course of sap flow and seasonal differences were similar with those of solar radiation. Sunrise is earlier and sunset is later in summer than it is in spring and autumn, the stem sap flow starts earlier and valley comes later corresponding in summer than it is in spring and autumn. A. truncatum belongs to high water consumption type in spring, the mean sap flow rates are as the followings: 0.001 88 cm/s in spring, 0.001 12 cm/s in summer, and 0.000 86 cm/s in autumn. The stem sap flow rates are obviously different in direction, and the biggest sap flow among different directions at the same stem is 122.1% of their mean, while the smallest is 86.3% of their mean. The difference of sap flow in direction on the same tree is stable, while the biggest and the smallest flow is not in the same direction on different trees. The direction difference has nothing to do with the width of the tree crown. The fluctuating rhythm of sap flow at the upper of stem is earlier than that of the lower and middle. The order of velocity at different trunk heights is upper>middle>lower.