毛竹种群向常绿阔叶林扩张的细根策略

为了探讨毛竹(Phyllostachys pubescens)种群向常绿阔叶林扩张的根系策略,该文采用根钻法和内生长法,在江西大岗山选取毛竹林与阔叶林的交错区——竹阔界面(bamboo-broad-leaved forest interface),并垂直于界面连续设置毛竹林、毛竹与阔叶树的混交林(以下简称为竹阔混交林)、常绿阔叶林3种样地,比较分析其细根的空间分布格局、比根长、根长密度、生长速率和周转率等指标.结果表明:毛竹林细根生物量(1 201.60 g·m-2)＞竹阔混交林(601.18 g·m-2)＞常绿阔叶林(204.88g·m-2);在毛竹与阔叶树竞争的混交林中,毛竹细根分布趋向于上层土壤(与毛竹林细根相比),且其比根长也显著增加,平均增幅高达123.42％,总根长密度比阔叶树大2.1倍;同时,毛竹细根生长速率和周转率均高于阔叶树.这些结果说明毛竹可通过广布、精准、灵活、快速等细根竞争策略,提高资源获取能力,实现种群扩张.

Strategy of fine root expansion of Phyllostachys pubescens population into evergreen broadleaved forest

Aims Roots, particularly fine roots, play an important role in interspecies competition. Our objective was to study the spatial distribution, morphological characteristics and growth rates of fine roots in both bamboo (Phyllostachys pubescens) and broad-leaved trees to better understand the mechanisms of expansion of bamboo into evergreen broad-leaved forest.
Methods We continuously sampled P. pubescens forest (PPF), bamboo-broad-leaved mixed forest (BMF) and evergreen broad-leaved forest (EBF) perpendicular to a bamboo-broad-leaved forest interface on Dagang Mountain, Jiangxi Province, China. The live fine root biomass, specific root length (SRL), root length density (RLD), fine root growth and turnover rates were comparatively analyzed by soil core and ingrowth methods.
Important findings Fine root biomass of PPF (1 201.60 g·m^–2) was much larger than that of BMF (601.18 g·m^–2) and EBF (204.88 g·m^–2). Vertical stratification of bamboo fine roots in BMF was found to shift from lower to upper soil layers, SRL of bamboo significantly increased by 123.42% and average RLD of bamboo was 210.0% greater than that of broad-leaved trees. In addition, both growth and turnover rates of bamboo fine roots were faster than those of trees. Findings indicated that P. pubescens, with wide, precise, flexible and fast nutrient access and space-occupation abilities, would outcompete trees belowground, resulting in expansion of its population into evergreen broad-leaved forest.