塔克拉玛干沙漠南缘三种防护林植物根系构型及其生态适应策略

Root architecture and ecological adaptation strategies in three shelterbelt plant species in the southern Taklimakan Desert

采用全根挖掘法挖取塔克拉玛干沙漠南缘3种主要防护林植物种——多枝柽柳(Tamarix ramosissima)、梭梭(Haloxylon ammodendron)和新疆杨(Populus alba var.pyramidalis)成年植株根系,测定并分析了根系构型及其拓扑结构。结果表明:1)多枝柽柳和梭梭的根系趋向于鱼尾状分支结构,新疆杨根系为叉状分支结构,根系分支结构的差异使其资源获取能力和对环境的适应能力有所差异;2)三种植物最小的根系平均连接长度为33.67 cm,多枝柽柳和梭梭的根系连接长度大于新疆杨,增加连接长度对植物在资源贫瘠的沙质土壤环境的生存有利;3)新疆杨的根系分支率显著高于多枝柽柳和梭梭,但其对干旱的适应性不如多枝柽柳和梭梭。4)三种植物根系分支均遵循Leonardo da Vinci法则,且不受根系直径的约束。三种防护林植物在水、养资源获取与土壤空间拓展方面具有差异性,表明在相似的极端干旱环境中3种植物采取了不同的生态适应策略。

Aims Root architectural properties influence the efficiency and cost of resource exploitation of plants. This paper aims to investigate the root topological properties and ecological adaptation strategies of three plant species which play important roles in wind shelterbelt in the southern Taklimakan Desert of China.Methods We excavated the coarse root systems of three shelterbelt plant species （Tamarix ramosissima, Haloxylon ammodendron, Populus alba var. pyramidalis） at a study site in the southern Taklimakan Desert and analyzed their root architectural properties, including topology, root length, diameter, and scaling relations.Important findings We found differences as well as similarities in the topological structure of root systems among the three plant species. The differences in root structure reflected different adaptation strategies among the plants to soil environment. The root branching order in both T. ramosissima （qa = 0.46, qb = 0.13, TI = 0.84, qa and qb show normed values corresponding to parameters a and b, respectively, TI shows topological index） and H. ammodendron （qa = 0.63, qb = 0.19, TI = 0.90） resembled the herringbone structure; whilst it was dichotomous in P. alba var. pyramidalis （qa = 0.03, qb = 0.02, TI = 0.49）. The main root length in the three plant species was all very along. Longer root length could reduce the internal competition of roots for nutrients, so that plants were better cope with the resource-poor sandy soil environment. The Leonardo da Vinci theory is supported in this study with the three plant species.