晋西黄土区不同林分类型和密度条件下林下灌草组成及多样性特征

Composition and diversity of understory plants under different stand types and densities in loess region of western Shanxi Province

【目的】研究晋西黄土区刺槐Robinia pseudoacacia人工林、油松Pinus tabulaeformis人工林、刺槐-油松人工混交林、山杨Populus davidiana-栎类Quercus spp.天然次生林的植物组成及植物多样性指标,探讨不同林分类型、不同密度条件下灌草植物多样性,为晋西黄土区植被建设和功能提升提供理论基础。【方法】通过野外调查,对低密度(800~1200株·hm^(−2))、中密度(1200~1600株·hm^(−2))、高密度(1600~2000株·hm^(−2))条件下22~25年生的4种林分林下灌草植物组成与植物多样性进行分析。【结果】①4种林分灌草植物共87种,隶属36科69属,其中灌木植物46种,隶属22科36属,草本植物41种,隶属17科33属。4种林分林下灌木和草本植物种数均在中密度时最多,表现为山杨-栎类天然次生林最多,油松人工林最少,刺槐-油松人工混交林的灌木层植物种数处于较高水平,刺槐人工林草本层植物种数较刺槐-油松人工混交林丰富。②4种林分灌草植物随林分密度增大呈现由阳生向中生、阴生植物过渡的变化规律。主要优势灌木分别为黄刺玫Rosa xanthine、连翘Forsythia suspensa,主要优势草本是薹草Carex spp.、沿阶草Ophiopogon bodinieri。③不同林分类型灌木层和草本层植物多样性指数存在一定差异,山杨-栎类天然次生林和刺槐-油松人工混交林在中密度时的植物多样性优于人工纯林,且随林分密度增大,灌木层和草本层植物多样性指数整体上呈现先增大后减小的变化趋势。【结论】研究区山杨-栎类天然次生林和刺槐-油松人工混交林在中密度时植物组成复杂且具有较高的植物多样性。建议通过人工抚育调整林分密度,并向中密度刺槐-油松人工混交林或近自然林进行改造,为黄刺玫、连翘等灌木植物及薹草、沿阶草等草本植物建立良好生长条件,同时保护研究区的山杨-栎类天然次生林,以促进植被恢复,强化其水土保持功能。图1表4参26。

[Objective]The objective is to study the plant composition and diversity index of Robinia pseudoacacia plantation,Pinus tabulaeformis plantation,R.pseudoacacia-P.tabulaeformis mixed forest,and Populus davidiana-Quercus natural secondary forest in the loess area of western Shanxi Province,and to explore the diversity of shrubs and herbaceous plants under different stand types and different densities,so as to provide theoretical basis for vegetation construction and function improvement in the loess region of western Shanxi.[Method]Through field investigation,the composition and diversity of understory plants were analyzed in 4 stands aged 22−25 years under the conditions of low density(800−1200 plants·hm^(−2)),medium density(1200−1600 plants·hm^(−2))and high density(1600−2000 plants·hm^(−2)).[Result](1)There were 87 species of shrubs and herbaceous plants in the 4 forests,belonging to 36 families and 69 genera,including 46 species of shrubs in 22 families and 36 genera,and 41 species of herbs in 17 families and 33 genera.The number of understory shrubs and herbaceous plants was the largest at medium density,showing that the natural secondary forest of P.davidiana-Quercus was the highest,and the artificial forest of P.tabulaeformis was the least.The number of plant species in the shrub layer of R.pseudoacacia-P.tabulaeformis mixed forest was at a high level,and the number of plant species in the grass layer of R.pseudoacacia was more abundant than that in R.pseudoacacia-P.tabulaeformis mixed forest.(2)The shrub and herbaceous plants in the 4 stands showed a transition pattern from sunny to mesophytic and shade plants with the increase of stand density.The dominant shrubs were Rosa xanthine and Forsythia suspensa,and the dominant herbs were Carex spp.and Ophiopogon bodinieri.(3)There were certain differences in plant diversity index between shrub layer and herb layer in different stand types.The plant diversity of P.davidiana and Quercus natural secondary forest and R.pseudoacacia-P.tabulaeformis mixed forest at medium density was better than that of pure artificial forest,and with the increase of stand density the plant diversity index of shrub layer and herb layer as a whole showed a trend of first increasing and then decreasing.[Conclusion]P.davidiana-Quercus natural secondary forest and R.pseudoacacia-P.tabulaeformis mixed forest in the study area have complex plant composition and high plant diversity at medium density.It is recommended to adjust the stand density by artificial tending,and transform it into medium-density R.pseudoacacia-P.tabulaeformis mixed forest or near-natural forest,protect P.davidiana-Quercus natural secondary forest in the study area for better vegetation restoration and soil and water conservation function.[Ch,1 fig.4 tab.26 ref.]