毛竹林下苦参和决明幼苗生长和生物量分配的立竹密度效应

Growth and biomass allocation of Sophotora flavescens and Catsia tora seedlings beneath moso bamboo forest in response to moso bamboo density

为明确毛竹(Phyllostachys edulis)-苦参(Sophotora flavescens)、毛竹-决明(Catsia tora)复合经营适宜的立竹密度,以立地条件和经营水平一致的3种立竹密度D1(1600±200株·hm^(-2))、D2(2400±200株·hm^(-2))、D3(3200±200株·hm^(-2))毛竹林下种植的固氮植物苦参和决明实生幼苗为试验对象,调查了不同立竹密度下苦参和决明幼苗的生长指标和生物量积累以及分配规律。结果表明:毛竹林下苦参和决明幼苗的株高、地径及叶生物量、茎生物量、豆荚生物量、根生物量、地上生物量、全株生物量均随立竹密度的增大而降低,且D1立竹密度显著高于D2、D3立竹密度;苦参幼苗叶重比、豆重比随立竹密度的增大呈"∧"型变化,根重比、根冠比呈"∨"型变化,茎重比呈持续下降趋势且D1立竹密度显著高于D2、D3立竹密度(P<0.05),除茎重比外,其他生物量比在不同立竹密度毛竹林间均无显著差异(P>0.05)。而随立竹密度的增大,决明幼苗茎重比、根重比、根冠比的变化趋势与苦参相同,而叶重比和豆重比呈持续增大趋势,且D1、D2与D3立竹密度间差异显著(P<0.05);主成分和R型因子综合评定法分析表明3种立竹密度毛竹林下苦参和决明幼苗生长和生物量分配的综合得分大小顺序为D1>D2>D3立竹密度。研究表明,立竹密度对毛竹林下苦参和决明幼苗的生长和生物量分配有重要影响,从试验毛竹林立竹密度来分析,毛竹-苦参、毛竹-决明复合经营适宜的立竹密度为D1(1600±200株·hm^(-2))。

To explore the suitable stand density of moso bamboo （Phyllostachys edulis） in the agroforestry systems of bamboo-Sophotora flavescens and bamboo-Catsia tora, we investigated the growth and biomass of two nitrogenfixing species, S. flavescensandC. tora, under three moso bamboo densities, D1 （1600±200 stems·hm-2）, D2 （2400±200 stems·hm-2） and D3 （3200±200 stems·hm-2） with the same site conditions and management levels. The results showed that plant height, basal diameter, tissue biomass and total biomass of both species all decreased with the increases of moso bamboo density. The decreased amplitude followed the order of D3〉D2〉D1. The biomass proportions of leaf and bean of S. flavescensshowed an inverted V shaped pattern, while the root biomass proportion and root/shoot ratio varied with a Vshaped pattern, and the stem biomass proportion decreased linearly with the increases of bamboo density. Except for the stem, the biomass proportions of other organs had no significant differences （P〉0.05） among three bamboo densities. With the increases of moso bamboo density, stem biomass proportion, root biomass proportion and root/shoot ratio ofC. tora seedlings showed a similar trend to that of theS. flavescensseedlings. The proportions of leaf biomass and bean biomass showed an increase trend, with the values in D1 being significantly higher than that of D2 and D3 （P〈0.05）.Results from the principal component analysis and Rtype factor analysis showed that the comprehensive scores of growth and biomass allocation of bothS. flavescens and C. tora followed the order of D1〉D2〉D3. Our results indicated that the bamboo density had negative effects on the growth and biomass allocation ofS. flavescens andC. tora seedlings. D1 （1600±200 stems·hm-2） would be the suitable bamboo density for the management of both agroforestry systems.