毛竹扩张对濒危植物桫椤根系形态可塑性的影响

为探讨毛竹(Phyllostachys heterocycla)向桫椤(Alsophila spinulosa)林扩张的根系形态可塑性变化,在赤水桫椤国家级自然保护区毛竹-桫椤混交林上分别设置受毛竹轻度、中度以及重度干扰的样地,用根钻法收集桫椤、毛竹根系并对其生物量密度、细根比根长、相邻同级侧根节点距等参数进行比对。结果表明:各干扰程度下桫椤根系生物量密度均远低于毛竹,且二者呈负相关;随着与毛竹的接近,桫椤根系生物量持续下降;各样地中毛竹细根比根长均高于桫椤;重度干扰下毛竹侧根节点距最小,侧根数目最多;且毛竹根系多分布于表层土壤。由此可见,桫椤根系逐渐趋向于分布在深层土壤,毛竹在向桫椤林扩张过程中可通过改变根系生物量密度、细根比根长、相邻同级侧根节点距等形态可塑性特征来占据优势。

Effects of Phyllostachys heterocycla expansion on morphological plasticity of endangered plant Alsophila spinulosa root system

In order to explore the root morphological plasticity of Alsophila spinulosa community affected by Phyllostachys heterocycla expansion,samples of mild,moderate and severe disturbance of Phyllostachys heterocycla were set up in Chishui Alsophila National Nature Reserve. The root systems of Alsophila spinulosa and Phyllostachys heterocycla were collected by root-drilling method. Their biomass density,specific root length of fine roots,and the distance between adjacent lateral roots were given detailed comparisons. The results showed that (1) The root biomass density of Alsophila spinulosa was much lower than that of Phyllostachys heterocycla under different impacts,displaying a negative correlation between them. (2) With the approaching of Phyllostachys heterocycla,the root biomass of Alsophila spinulosa continued to decline. (3) Fine root specific root length of Phyllostachys heterocycla was higher than that of Alsophila spinulosa in all plots. (4) The distance between lateral root nodes of Phyllostachys heterocycla was the shortest and the number of lateral roots was the largest under severe disturbance. (5) The roots of Phyllostachys heterocycla were mostly distributed in surface soil. Thus,we concluded that the root system of Alsophila spinulosa tended to be distributed in the deep soil gradually. In the process of expanding to Alsophila spinulosa forest,Phyllostachys heterocycla can maintain its dominance by changing the morphological plasticity characteristics of root biomass density,fine root specific root length,and adjacent lateral root node spacing.