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(xué),、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(zhì)部水力學(xué)特征研究方面獲得新進(jìn)展,。相關(guān)成果發(fā)表于《全球生態(tài)學(xué)與生物地理學(xué)快報(bào)》,。
據(jù)了解，樹木木質(zhì)部的結(jié)構(gòu)決定其運(yùn)輸水分效率,、安全性和機(jī)械強(qiáng)度,，已有假說(shuō)認(rèn)為這三者存在權(quán)衡關(guān)系。因此,，認(rèn)識(shí)這種權(quán)衡關(guān)系及其與環(huán)境的聯(lián)系,，對(duì)認(rèn)識(shí)樹木的生態(tài)適應(yīng)特征、進(jìn)化具有重要意義,。
“我們分析了云南省境內(nèi)316種被子植物樹木的木質(zhì)部結(jié)構(gòu)特征,、潛在導(dǎo)水率及機(jī)械強(qiáng)度和氣候因子的關(guān)系,。”張石寶告訴記者，結(jié)果發(fā)現(xiàn)這些樹種的導(dǎo)管特征,，如導(dǎo)管密度,、導(dǎo)管內(nèi)徑大小和潛在導(dǎo)水率的差異，遠(yuǎn)大于木材密度和力學(xué)特征,，木質(zhì)部的潛在導(dǎo)水率與機(jī)械強(qiáng)度不相關(guān),。
研究發(fā)現(xiàn)，導(dǎo)管內(nèi)徑大小和潛在導(dǎo)水率,、樣木生長(zhǎng)地的年平均溫度正相關(guān),，導(dǎo)管密度與年均溫負(fù)相關(guān)。常綠樹的導(dǎo)管密度與干旱指數(shù)正相關(guān),，潛在導(dǎo)水率,、抗壓強(qiáng)度與干旱指數(shù)負(fù)相關(guān)，木材密度,、抗壓強(qiáng)度與年均溫正相關(guān),，而落葉樹并沒(méi)有這些相關(guān)。
結(jié)果表明,，常綠樹的木質(zhì)部發(fā)育對(duì)環(huán)境變化比落葉樹敏感,，導(dǎo)水效率與機(jī)械強(qiáng)度不存在權(quán)衡關(guān)系，落葉樹相對(duì)不敏感可能是由于被子植物木質(zhì)部機(jī)械穩(wěn)定性和導(dǎo)水功能相互獨(dú)立的緣故,。該結(jié)果對(duì)探討森林生態(tài)系統(tǒng)服務(wù)與功能以及常綠樹與落葉樹對(duì)環(huán)境變化的響應(yīng)有重要參考價(jià)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.
