日前，从中科院昆明植物所获悉，该所研究员张石宝与广西大学、中科院西双版纳热带植物园的研究人员合作，在阔叶树木质部水力学特征研究方面获得新进展。相关成果发表于《全球生态学与生物地理学快报》。
据了解，树木木质部的结构决定其运输水分效率、安全性和机械强度，已有假说认为这三者存在权衡关系。因此，认识这种权衡关系及其与环境的联系，对认识树木的生态适应特征、进化具有重要意义。
“我们分析了云南省境内316种被子植物树木的木质部结构特征、潜在导水率及机械强度和气候因子的关系。”张石宝告诉记者，结果发现这些树种的导管特征，如导管密度、导管内径大小和潜在导水率的差异，远大于木材密度和力学特征，木质部的潜在导水率与机械强度不相关。
研究发现，导管内径大小和潜在导水率、样木生长地的年平均温度正相关，导管密度与年均温负相关。常绿树的导管密度与干旱指数正相关，潜在导水率、抗压强度与干旱指数负相关，木材密度、抗压强度与年均温正相关，而落叶树并没有这些相关。
结果表明，常绿树的木质部发育对环境变化比落叶树敏感，导水效率与机械强度不存在权衡关系，落叶树相对不敏感可能是由于被子植物木质部机械稳定性和导水功能相互独立的缘故。该结果对探讨森林生态系统服务与功能以及常绿树与落叶树对环境变化的响应有重要参考价值。（生物谷 Bioon.com）
生物谷推荐的英文摘要
Global Ecology and Biogeography DOI: 10.1111/geb.12056
Potential hydraulic efficiency in angiosperm trees increases with growth-site temperature but has no trade-off with mechanical strength
Shi-Bao Zhang1,3,†, Kun-Fang Cao2,3,†,*, Ze-Xin Fan3, Jiao-Lin Zhang3
Abstract
Aim
Xylem structures are closely related to a tree's hydraulic efficiency and mechanical stability, both of which affect the life history and ecological strategy of a species. Although mechanical strength and hydraulic capacity can be shaped by the environment, no such associations between hydraulic efficiency and climatic variables have been reported across a wide range of tree species.
Location
Yunnan, south-west China.
Methods
We compiled a data set for vessel density, vessel diameter (D), potential hydraulic conductivity (Kp), wood density (WD), modulus of rupture (MOR) and modulus of elasticity (MOE) from 316 angiosperm tree species. Our objective was to examine the correlations among xylem traits and climatic variables. We hypothesized that both hydraulic efficiency and mechanical strength would vary along climatic gradients, but that a trade-off would occur between them.
Results
All xylem traits varied significantly across species, but the magnitudes of variation were greater for vessel traits than for mechanical properties. Values for Kp and D increased with mean annual temperature (MAT) in both evergreen and deciduous trees, but they were significantly correlated with aridity index (AI) in evergreen species only. Both WD and MOR were significantly correlated with MAT only in evergreen trees. MOR decreased with increasing AI in the evergreens, but not in deciduous trees. These findings indicated that xylem development in evergreens is more sensitive to environmental changes than in deciduous trees. However, stem hydraulic traits are independent of mechanical properties.
Main conclusions
Consistent with our hypothesis, both hydraulic efficiency and mechanical strength of angiosperm trees are influenced by the environment, with temperature having a more important effect on hydraulic efficiency than precipitation. However, no trade-off exists between efficiency and strength. This absence of a link is explained because angiosperms have xylem tissue that specifically functions in either mechanical strength or water transport.
