黄土丘陵区典型树木抵抗空穴化能力及与木质部结构的关系

以黄土丘陵区7种典型落叶乔灌木(山杨、辽东栎及刺槐,狼牙刺、黄刺玫、山桃和荆条)为对象,研究了其抵抗空穴化形成的能力与木质部解剖结构和木材密度的关系。结果表明:1)7种乔灌木中,狼牙刺和黄刺玫抵抗空穴化形成的能力最强;其次为山桃、荆条和山杨;而刺槐和辽东栎抵抗空穴化形成的能力最弱。2)7种植物中,黄刺玫、山杨和山桃的导管密度明显高于其他物种,而辽东栎、刺槐和荆条的导管密度相对较小,最大值(黄刺玫)为最小值(刺槐)的近10倍;导管腔平均直径以刺槐为最大,而黄刺玫和狼牙刺的导管直径最小,最大值为最小值(黄刺玫)的3倍左右;导管密度和导管腔平均直径之间呈显著负相关关系。7种植物的木材密度介于0.43～0.70g/cm3之间,其中以狼牙刺的为最大,以山杨的为最小,比值为1.6倍。4种灌木的平均木材密度显著高于3种乔木。3)不同植物抵抗空穴化形成的能力与导管腔平均直径呈显著负相关,而与木材密度之间也存在一定的正相关关系,因而二者可用作黄土丘陵区不同植物抵抗空穴化形成能力的评价指标。

Cavitation resistance of dominant trees and shrubs in Loess hilly region and their relationship with xylem structure

The relationship between cavitation resistance and anatomical structure of xylem as well as wood density was studied in seven dominant deciduous wood species (three trees: Populus davidiana, Quercus liaotungensis, Robinia pseudoacacia and four shrubs: Sophora viciifolia, Rosa xanthina, Prunus davidiana and Vitex negundo ) in the Loess hilly region, Shaanxi Province. The results indicate that 1) Sophora viciifolia and Rosa xanthina had the strongest cavitation resistance, followed by Prunus davidiana, Vitex negundo and Populus davidiana, while Robinia pseudoacacia and Quercus liaotungensis were the most vulnerable to embolism. 2) Rosa xanthina, Populus davidiana and Prunus davidiana had relatively higher xylem density, while Quercus liaotungensis, Robinia pseudoacacia and Vitex negundo had lower xylem density. The maximum density of xylem (Rosa xanthina) was nearly 10 times the minimum (Robinia pseudoacacia). The mean diameter of vessel lumen in Robinia pseudoacacia was the largest, while it was the smallest in Rosa xanthina and Sophora viciifolia, where the maximum was about 3 times the minimum(Rosa xanthina). The density of xylem was negatively correlated with the mean diameter of vessel lumen. Wood density ranged from 0.43 g/cm3 to 0.70 g/cm3, with the largest values in Sorphora viciifolia and the minimum in Populus davidiana, where the ratio of the two extreme values was 1.6. Mean wood density of the four shrubs was larger than that of the three tree species. Cavitation resistance was negatively correlated with mean diameter of vessel lumen and positively correlated with wood density, indicating both indices can be used to select wood species with strong cavitation resistance in the Loess hilly region.