胡杨枝条水力结构特征在雌雄间的比较分析
Comparative Analysis of the Hydraulic Structure Characteristics of Populus euphratica Oliv. Branches between Male and Female

植物枝条水力结构特征能够反映植物水分运输能力，对了解树木生存与竞争乃至森林稳定性具有重要的生态学意义。在同一生境中比较胡杨雌、雄株枝条水力结构特征随冠层高度变化的雌雄差异，探讨胡杨雌雄株比导率(Ks)、叶比导率(Kl)、导水率丧失百分比(percent loss of hydraulic conductivity, PLC)、胡伯尔值(Hv)等水力结构参数与冠层高度的关系。结果表明：1) 随着冠层高度的增加，胡杨雌雄株枝条平均PLC随高度变化各异，变化范围在30%~55%之间，Ks和Kl逐渐增加，Hv表现出减少的趋势。2) 在同一冠层高度下，雄株枝条Ks、Kl显著高于雌株，表现出雄株水分运输效率较雌株高，且枝条末端叶片供水情况较好；雌株枝条Hv显著高于雄株，表明雌株枝条用于维持叶片水分的茎干组织在数量上较雄株多。说明在相同冠层高度下，雄株枝条导水效率显著高于雌株。3) 相关分析表明，胡杨雌雄株水力结构参数的变化和冠层高度密切相关，此外，这种变化与木质部横截面积大小有关。总之，胡杨雌雄株枝条导水率随不同冠层高度而变化，雄株比雌株表现出的导水能力更强。
The hydraulic structural characteristics of plant branches can reflect the water transport capacity of plants, which is of great ecological importance for understanding tree survival and competition and even forest stability. We compared the differences between male and female branches of Populus euphratica Oliv. with canopy height in the same habitat, and investigated the relationship between hydraulic structural parameters such as specific conductivity (Ks), leaf specific conductivity (Kl), percent loss of hydraulic conductivity (PLC), and Huber value (Hv) and canopy height in both male and female Populus euphratica plants. The results showed that: 1) With the increase of canopy height, the mean PLC of branches of both male and female Populus euphratica plants varied with height, ranging from 30% to 55%, Ks and Kl gradually increased, and Hv showed a decreasing trend. 2) Under the same canopy height, Ks and Kl of male branches were significantly higher than those of female plants, showing that male plants had higher water transport efficiency than female plants and better water supply to the leaves at the end of branches; Hv of female branches was significantly higher than that of male plants, indicating that female branches had more stem tissues for maintaining water in the leaves in terms of quantity than male plants. This indicates that the water conductivity of male branches is significantly higher than that of female branches under the same canopy height. 3) Correlation analysis showed that the variation of hydraulic structural parameters in both male and female Populus euphratica plants was closely related to canopy height, and in addition, this variation was related to the size of xylem cross-sectional area. In conclusion, the hydraulic conductivity of branches of male and female poplar plants varied with different canopy heights, and male plants exhibited better hydraulic conductivity than female plants.