日前，從中科院昆明植物所獲悉,，該所研究員張石寶與廣西大學,、中科院西雙版納熱帶植物園的研究人員合作，在闊葉樹木質部水力學特征研究方面獲得新進展,。相關成果發(fā)表于《全球生態(tài)學與生物地理學快報》,。
據(jù)了解，樹木木質部的結構決定其運輸水分效率,、安全性和機械強度，已有假說認為這三者存在權衡關系,。因此,，認識這種權衡關系及其與環(huán)境的聯(lián)系，對認識樹木的生態(tài)適應特征,、進化具有重要意義,。
“我們分析了云南省境內316種被子植物樹木的木質部結構特征、潛在導水率及機械強度和氣候因子的關系,。”張石寶告訴記者,，結果發(fā)現(xiàn)這些樹種的導管特征，如導管密度,、導管內徑大小和潛在導水率的差異,，遠大于木材密度和力學特征，木質部的潛在導水率與機械強度不相關,。
研究發(fā)現(xiàn),，導管內徑大小和潛在導水率、樣木生長地的年平均溫度正相關,，導管密度與年均溫負相關,。常綠樹的導管密度與干旱指數(shù)正相關,，潛在導水率、抗壓強度與干旱指數(shù)負相關,，木材密度,、抗壓強度與年均溫正相關，而落葉樹并沒有這些相關,。
結果表明,，常綠樹的木質部發(fā)育對環(huán)境變化比落葉樹敏感，導水效率與機械強度不存在權衡關系,，落葉樹相對不敏感可能是由于被子植物木質部機械穩(wěn)定性和導水功能相互獨立的緣故,。該結果對探討森林生態(tài)系統(tǒng)服務與功能以及常綠樹與落葉樹對環(huán)境變化的響應有重要參考價值。（生物谷 Bioon.com）
生物谷推薦的英文摘要
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.
