塔克拉玛干沙漠腹地3种植物根系构型及其生境适应策略

 在塔克拉玛干沙漠腹地, 采用挖掘法挖取塔克拉玛干柽柳(Tamarix taklamakanensis)、塔克拉玛干沙拐枣(Calligonum roborovskii)和罗布麻(Apocynum venetum )根系, 对根系的拓扑结构特征进行了测定与分析。结果表明: 1) 3种植物根系均以水平分布占优势, 根系浅层化。2) 3种植物根系结构的适应性不同, 表现为两种不同的根系分支模式, 塔克拉玛干柽柳根系为叉状分支结构(q_a=0.15、q_b=0.09、TI=0.658), 罗布麻(q_a=0.43、q_b=0.35、TI=0. 83)和沙拐枣(q_a=0.52、q_b=0.38、TI=0.86)根系趋向于鱼尾形分支结构。3) 3种植物根系的连接长度都较大, 最小也达1.12 m, 说明在塔克拉玛干沙漠腹地, 3种植物通过增加连接长度来扩大根系在土层中的分布范围, 从而提高根系的有效营养空间, 增加根系连接长度是根系对沙漠腹地贫瘠土壤环境的一个良好适应。4)研究验证了Leonardo da Vinci法则, 即根系分支前的横截面积等于根系分支后的横截面积之和, 3种植物根系分支前后的横截面积符合Leonardo da Vinci法则。研究表明沙漠腹地3种植物根系构型特征既有相似性又有差异性, 在相似的沙漠环境中具有不同的根系适应策略。

ANALYSIS OF ROOT ARCHITECTURE AND ROOT ADAPTIVE STRATEGY IN THE TAKLIMAKAN DESERT AREA OF CHINA

Aims Root architectural properties can be divided into geometric properties and topological properties. Topological properties are believed to influence the efficiency and costs of resource exploitation in terms of carbon required for root segment construction. Methods We excavated by shovel the coarse root systems of three natural species of the Taklimakan Desert area (Tamarix taklamakanensis, Calligonum roborovskii and Apocynum venetum) and analyzed aspects of root architecture, including topology, link length, diameter and scaling relations. Important findings Root distribution was dominated by horizontal roots. Root branching pattern differed by species, with the shrub T. taklamakanensis tending to be dichotomous (q_a=0.15, q_b=0.09, TI=0.658) and C. roborovskii (q_a=0.52, q_b=0.38, TI=0.86) and A. venetum (q_a=0.43, q_b=0.35, TI=0.83) being herringbone-like. The lengths of links were very long for all species, with the shortest being 1.12 m. The different architectural strategies could be explained in terms of cost-benefits relations and efficiency in soil resource exploration and exploitation. We concluded that the differences and similarities of root architecture reflected strategy in exploitation and exploration. We also tested the “pipe-stem” theory, essentially dating back to Leonardo da Vinci, that underlies many models and found that our measurement data conformed with it. The ratio of the sum of root cross-sectional areas after and before bifurcation was constant with change of root diameters, so we proposed that the scaling coefficient is the universal feature of root architecture.