华南地区常见树种导管特征与树干液流的关系

Relationship between Vessel Characteristics and Sap Flow of Eight Subtropical Tree Species

摘要:

为探讨树木结构与功能的关系,对华南地区常见8 种树木边材的导管特征进行观察,并利用Granier 热扩散探针法测量干、湿季树干的液流密度,分析导管特征与树干液流的关系。结果表明,除红锥(Castanopsis hystrix)有两种导管外,大叶相思(Acacia auriculaeformis)、荷木(Schima superba)、火力楠(Michelia macclurei)、藜蒴(C. fissa)、马占相思(A. mangium)、柠檬桉(Eucalyptus citriodora)、尾巨桉(E. urophylla×E. grandis)的导管类型单一。导管特征在种间存在明显差异,且导管长度、密度和孔径之间存在明显相关性,它们与标准化的边材面积呈现显著相关。湿季液流最大值与导管特征无明显相关性,但整树最大蒸腾速率与导管特征呈显著相关;树木的日蒸腾量与导管特征也有明显相关性。因此,树木的液流速率并不受树干的导管影响;而树干的导管孔径与边材面积间的负相关权衡机制,可以降低树种间由于导管孔径差异引起的树干的水分输送速率的差异性。

Abstract:

In order to understand the relationship between tree structure and its function, the vessel characters of sap wood of eight tree species, Acacia auriculaeformis, Schima superba, Michelia macclurei, Castanopsis hystrix, C. fissa, A. mangium, Eucalyptus citriodora and E. urophylla×E. grandis and their stem sap flux densities in wet and dry season monitored by using Granier's thermal dissipation probe method, were investigated in subtropical south China. The results showed that vessels were of single-type in these tree species except for M. macclurei that had two types of vessels. The vessel length, density and lumen diameter were significantly different among the eight tree species, and obvious relationships among the three vessel characters were observed. The normalized area of sap wood had significant relation with the vessel characters. No significant relation of the maximum sap flow with vessel characters was found, but it existed between the maximum whole tree transpiration rate and the vessel characters in wet season, and so did that of the daily total transpired amount with the vessel characters. Therefore, the vessel in trunk had no influence on sap flow rate, the negative trade-off relation between vessel diameter and sapwood area of trunk could the difference in water transpiration rate of trunk caused by the difference of vessel diameter of the tree species.