金沙江干热河谷主要植被恢复树种叶水势的时空变化规律
Spatial and Temporal Variations of Water Poten tia l of theMa in Tree Spec iesfor Vegeta tion Restora tion in the Dry-hot Va lleys of the Jin sha River
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摘要: 2005年和2006年在金沙江干热河谷,选择不同季节的典型晴天测定了18个试验树种的叶水势,结果表明:(1)金沙江干热河谷主要植被恢复树种叶水势在不同季节的日变化曲线均有一个明显的高峰,绝大多数呈单峰状分布,高峰值大多数出现在下午14: 00;干热生境中的树种具有丰富的叶水势多样性。(2)元谋干热河谷主要树种的叶水势受季节变化的影响较大,所有树种均表现为3月份叶水势大于5月份叶水势以及5月份叶水势小于10月份水势, 5月干热胁迫的加深加剧了树种间水势的进一步分化,而雨季后干热胁迫的解除能降低分化的程度;各树种叶水势日变化在干热的5月份变动幅度最小。(3)各树种叶水势与温度、湿度及光照强度分别呈负、正、负相关,相关性可由线性方程予以恰当描述。(4)不同海拔区域所引起的环境因子与物候的差异能影响到某些树种水势的日变化幅度以及季节变化规律;以坡位而言,相对低的坡位有利于各树种叶水势维持在一个相对高的水平;印楝在3种混交模式中叶水势高低依次为:印楝与大叶相思>印楝与银合欢>印楝与久树,这种排序与印楝所受到的竞争强烈程度紧密相关,极度的干热环境降低了不同混交模式对植物水势的影响程度;灌溉有利于缓解或解除5月极度干热所形成的水分胁迫。Abstract: The spatial and temporal variations of water potential of 18 tree species for vegetation restoration in thedry-hot valleys of the J insha riverwere systematically analyzed on typ ical sunny day of different seasons in 2005 and2006, some main conclusionswere gotten as follows: (1) The daily water potentials within leaves of the main treespecies in the dry-hot valleys of the Jinsha river all obviously p resented a figure of single2peak in different seasons,the most peak values of dailywater potentials of the leaves appeared at 14: 00; (2) The water potentialwithin leavesof the main tree species in the valleys was deep ly affected by the change of seasons, the characteristic seasonalchange ofwater potentialwithin leaves for all the tree species studied was that the water potential inMarch was bigger than water potential inMay and water potential inMaywas smaller than water potential in October; the dry andhot inMay p romoted the diversity ofwater potential, and the relief of dry and hot stress after rainy season decreasedthe diversity; the diurnal variation of water potentialwithin leaves of the tree species inMay was relatively stable.(3) The water potential within leaves had the negative, positive and negative linear correlation with temperature, humidity and light intensity. (4)Different tree specieswere differently affected by altitude, the change of environmental factors and phenology caused by changeable altitude could affect the diurnal and seasonal variation of waterpotentials of some tree species; the lower location of slope was beneficial to keep ingwater potential at a relative highlevel; the order of leaf water potential of Azad irachta indica in three mixed stands from high to low was Azad irachtaindica & Acacia auric, Azadirach ta indica & Leucaena leucojpha la, and Azadirachta indica & Sctdeichera oleosa,which was closely related to the supp ressed condition of Azadirachta ind ica, the extremely dry and hot environmentcould decrease the affection of differentmixed stands on p lant leafwater potential; the water stress caused by the extreme drought inMay could be relieved by irrigation.
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