毛竹和高节竹相互侵入后林分地下鞭根系统竞争效应

Rhizome and root competitive effects of bamboo in Phyllostachys edulis and Ph. prominens mixed forest

在毛竹和高节竹分布的界面区,由于相互侵入,常形成混交竹林,为比较毛竹、高节竹地下鞭根系统的可塑性和竞争能力,调查分析了毛竹、高节竹纯林及其混交林地下鞭根系统的形态结构特征和生物量分配规律。结果表明:高节竹鞭径、鞭节长、比根长、根长密度、根表面积密度、根体积密度和鞭生物量、根生物量、鞭根总生物量均显著低于毛竹,而比鞭长、鞭长密度和鞭节密度则相反,根径、分形维数差异不显著。高节竹与毛竹混交,会引起二竹种地下鞭根系统形态特征和生物量分配的明显变化,毛竹鞭径、鞭节长和高节竹鞭节长显著提高,毛竹鞭长密度、鞭节密度、比鞭长和高节竹鞭长密度、鞭节密度显著降低;毛竹、高节竹根长密度、表面积密度、体积密度、鞭生物量、根生物量、鞭根总生物量和根生物量比例显著下降,比根长和鞭生物量比例显著升高。毛竹、高节竹鞭根系统相对产量显著小于1,竞争平衡指数(高节竹/毛竹)显著小于0,且鞭根竞争平衡指数显著高于竹鞭。研究表明,毛竹比高节竹具有更高的地下鞭根系统可塑性,两竹种间存在激烈的种间竞争,毛竹竞争能力明显强于高节竹,鞭根在地下系统竞争中占主导作用。

Mixed forests of Phyllostachys edulis and Phyllostachys prominens are developing due to their mutual invasion in the adjacent distribution regions of these two bamboo species. To compare the plasticity and competition of Ph. edulis and Ph. prominens, a field experiment was conducted to explore the adaptive features of rhizome and roots of Ph. edulis and Ph. prominens in the pure and mixed forests. The results showed that rhizome diameter and node length, specific root length, densities of root length, tal rhizome and root biomass of surface area and volume, rhizome Ph. prominens were all lower than biomass, root biomass and to- those of Ph. edulis, while an opposite pattern was found for the specific rhizome length, and densities of rhizome length and rhizome node. No differences in root diameter and fractal dimension between the two bamboos were found. Morphological character and biomass allocation for rhizome-root system of Ph. edulis and Ph. Prominens changed after mutual invasion. Rhizome diameter of Ph. edulis and rhizome node length of the two bamboos increased, but densities of rhizome length and node of the two bamboos, specific rhizome length of Ph. edulis all decreased remarkably. Density of root length, surface area and volume, biomass of rhizome, root and total rhizome and root biomass of Ph. edulis and Ph. Prominens all decreased greatly, while specific root length and allocation proportion of rhizome for the two bamboos increased obviously. The relative yield for the two bamboos was significantly less than 1, and competitive balance index （Ph. prominens/Ph, edulis） was less than O. Furthermore, the competitive balance index of rhizome and root was significantly higher than that of rhizome. All those results indicated that rhizome-root system of Ph. edulis was more plastic than that of Ph. prominens. There was intense interspecific competition among the two bamboos in the mixed forest, and Ph. edulis was more competitive than Ph. prominens, and rhizome root system played a leading role in competition between Ph. edulis and Ph. prominens.