不同林龄桉树人工林林下物种多样性和生物量的动态变化

采用空间代替时间法和典型抽样法,以四川省威远县桉树(Eucalyptus robusta)人工林为研究对象,综合分析其林下植被物种组成及重要值、灌木层和草本层地上、地下和全株生物量以及物种多样性指数(Shannon-Wiener多样性指数H、Simpson优势度指数H′、丰富度指数D和Pielou均匀度指数JSW),探究林下植被的物种多样性和生物量在5个不同林龄(4,5,6,7,8年生)下的动态变化及二者之间的相关性。结果表明:调查到植物共有210种,隶属79科151属,草本层物种数多于灌木层。草本层的五节芒(Miscanthus floridulus)、芒萁(Dicranop?teris pedata)和灌木层的野牡丹(Melastoma malabathricum)、戟叶悬钩子(Rubus hastifolius)在不同林龄下都占据主要优势地位。随着林龄的增大,郁闭度加大,灌木层的D、H和H′值均表现为先增后减的规律;草本层D、H和H′值均呈先增后减再增再减的双峰趋势。草本层各生物量呈先增后减再增的变化趋势;灌木层各生物量呈先增后减的变化趋势。物种多样性与生物量呈显著正相关,草本层的D、H指数是影响生物量的直接因子。桉树人工林林下植被物种分布、组成、物种多样性和生物量对林龄变化的响应不同,表现为不同的动态特征规律,相关结果为我国西南地区桉树林管理提供了数据支撑。

Dynamic Changes of Undergrowth Species Diversity and Biomass of Eucalyptus robusta Plantations at Different Ages

By using the spatial replacement time and the typical sampling as methods,taking Eucalyptus robusta plantation in Weiyuan County,Sichuan Province as materials,we comprehensively analyzed the composition of the understory vegetation species and important value,and the aboveground,underground and whole plant biomass of the shrub and herb layers and species diversity index(Shannon-Wiener diversity index H,Simpson dominance index H′,richness index D and Pielou evenness index JSW),and explored the dynamic changes of species diversity and biomass of undergrowth vegetation at five different forest ages(4,5,6,7,8 years)and the correlation between them respectively.The results showed that:A total of 210 species were found,belonging to 79 families and 151 genera,with more species in the herb layer than in the shrub layer.The herb layer of Miscanthus floridulus,Dicranopteris pedata and shrub layer of Melastoma malabathricum and Rubus hastifolius all occupied the dominant position at different ages respectively.With the forest age increasing,the density canopy increased,the D value,H value and H′value of shrub layer all increased first and then decreased respectively;The D,H and H′values of the herb layer showed a trend of change of the bimodal curve after increased,then decreased,then increased and then decreased.The biomass of the herb layer increased first and then decreased and then increased,the biomass of shrub layer increased first and then decreased.There was a significant positive correlation between species diversity and biomass,the D and H indices of herb layer were the direct factors affecting biomass.The species distribution,composition,species diversity and biomass of undergrowth vegetation in Eucalyptus robusta plantation were different in response to changes in forest age,showing different dynamic characteristic rules,the results provided data support for Eucalyptus robusta forest management in southwest China.