长白山不同演替阶段温带森林木本植物菌根类型对林下草本植物多样性的影响

Effects of woody plant mycorrhizal types on understory herb diversity in temperate forests at different successional stages in Changbai Mountains

温带森林生态系统草本植物多样性丰富,是植物多样性的重要组分,对森林生态系统功能的调控同样具有重要作用,但却未受到广泛关注。本研究依托长白山地区原始阔叶红松(Pinus koraiensis)林和采伐干扰后形成的次生针阔混交林中共128个1 m×1 m草本植物样方连续两年的调查数据,深入解析了两类森林林下丛枝菌根(arbuscular mycorrhizal, AM)草本植物和非菌根(non-mycorrhizal, NM)草本植物多样性的异同;并运用广义线性混合效应模型分析了AM木本植物和外生菌根(ectomycorrhizal,EcM)木本植物以及环境因子对林下草本植物多样性的影响。结果表明:原始阔叶红松林中群落水平上草本植物和AM草本植物的多度和多样性均显著高于受人类采伐干扰后形成的次生针阔混交林,而NM草本植物无显著差异。林下草本植物多度和多样性受到木本植物邻体的显著影响,但其作用强度受到环境因素的调控。在次生针阔混交林中,群落水平上的草本植物多样性主要受木本植物邻体多样性和林下叶面积指数的直接影响。AM草本植物多度与EcM木本植物邻体密度显著负相关,且这种负作用关系随着土壤含水量的增加而减弱。在阔叶红松林中,土壤含水量直接影响群落水平草本植物和AM草本植物的多度,且土壤含水量的高低调控木本植物邻体对群落水平草本多度和多样性的影响。综上所述,采伐干扰显著降低了温带森林生态系统中草本植物多度和多样性,而上层木本植物邻体的菌根类型和环境因子对林下草本植物群落构建表现出明显的交互作用。

Aims:Herbaceous plants are an important part of plant diversity in temperate forests and play a critical role in regulating ecosystem functioning.However,the diversity patterns of understory herbaceous plants and their contributions to ecosystem functioning have long been neglected.Therefore here,we aimed to determine herbaceous plant diversity in temperate forests at different successional stages and tease apart the relative importance of woody plant mycorrhizal types and environmental variables in regulating the diversity of herbaceous plants.Methods:Based on continuous two-years survey data from 128 herbaceous plant quadrats(1 m×1 m)in temperate forests at two different successional stages(i.e.,the secondary conifer and broad-leaved mixed forests(CBF)and the broad-leaved Korean pine forests(BKF))in Changbai Mountains,we estimated the differences in diversity of herbaceous plant community,arbuscular mycorrhizal(AM)and non-mycorrhizal(NM)herbaceous plants in two forests.We also assessed the effects of AM and ectomycorrhizal(EcM)woody plants and environmental variables on the diversity of herbaceous plants using generalized linear mixed-effects model.Results:Our results showed that the abundance and diversity of herbaceous plants at the community level and AM herbaceous plants were significantly higher in the BKF than those in the CBF,while there was no difference of NM herbaceous plants between the two sites.The abundance and diversity of herbaceous plants were significantly influenced by woody plant neighbors,but the effects of woody plant neighbors were dependent on environmental variables.In the CBF,the diversity of herbaceous plant at the community level and AM herbaceous plants were directly affected by the diversity of woody plant neighbors and leaf area index.The abundance of AM herbaceous plants was negatively correlated with density of EcM woody plant neighbors,but the negative effect of EcM woody plant neighbors reduced with increasing in soil moisture.In the BKF,soil moisture directly influenced the abundance of herbaceous plants at the community level and AM herbaceous plants,and the impacts of woody plant neighbors on the abundance and diversity of herbaceous plants was also dependent on soil moisture.Conclusion:Overall,our findings indicate that forest disturbance could significantly decrease the abundance and diversity of understory herbaceous plants in temperate forest ecosystems,and provide insight into how the mycorrhizal types of overstory woody plant neighbors and environmental variables interactively modulate the community assembly of understory herbaceous plants.