不同更新方式巨尾桉林下植物群落变化及其环境解释

【目的】了解不同更新方式巨尾桉（Eucalytus grandis×E.urophylla）人工林下植物群落的变化规律。【方法】采用典范对应分析（CCA）,定量评价巨尾桉人工林下植物分布与更新方式和环境因子之间的关系。【结果】更新后5年,群落草本层和灌木层的物种丰富度均为植苗林〉萌芽林〉采伐迹地;草本层植物的ShannonWiener指数、Simpson指数和Pielou均匀度指数以植苗林为最高,采伐迹地次之,萌芽林最小;灌木层的Shannon-Wiener指数、Simpson指数和Pielou均匀度指数则以萌芽林为最高,植苗林次之,采伐迹地最小;方差分析结果表明,萌芽林与植苗林草本层植物之间的Shannon-Wiener指数、Simpson指数和Pielou均匀度指数存在显著差异（P〈0.05）,采伐迹地的Shannon-Wiener指数和Pielou均匀度指数明显低于萌芽林（P〈0.05）,其余均无显著差异。3种群落的物种组成存在显著差异,冠层透光系数、土壤孔隙度、坡向、速效磷对灌木层物种分布格局有重要的影响,4个环境因子的叠加效应总共解释了3种群落之间灌木层物种组成变异的90%以上;冠层透光系数、坡向、总氮/总磷、速效氮/速效磷、土壤孔隙度对草本层物种分布格局有重要影响,5个环境因子的叠加效应总共解释了3种群落之间草本层物种组成变异的86%。【结论】微生境的变化导致了不同更新方式巨尾桉人工林下植物组成的变化;适度干扰（不炼山、不施除草剂、带状整地、带状抚育）有利于林下植物多样性的维持。

Changes in Understory Plant Community of Eucalytus grandis×E.urophylla Plantation in Different Regeneration Modes and Associated Environmental Explanations

【Objective】The aim of this paper was to better understand the change regulation of understory plant communities of Eucalytus grandis×E.urophylla plantation in different regeneration modes.【Methods】The relationship between the distribution of understory plant and environmental factors were quantitatively assessed by the method of canonical correspondence analysis（CCA）.【Results】Five years after the regeneration,the species richness of herb layer and shrub layer of the community ranged as planting forest〉sprout forest〉cut-over land.The highest of Shannon-Wiener index,Simpson index and Pielou evenness index of the herb layer was obtained in planting forest,the second in cut-over land,and the smallest in sprout forest.The Shannon-Wiener index,Simpson index and Pielou evenness index of shrub layer was the highest in sprout forest,moderate in the planting forest,and minimum in cut-over land.Variance analysis results show that there were significant differences between the herb layer of sprout forest and planting forest on Shannon-Wiener index,Simpson index and Pielou evenness index（P〈0.05）.Shannon-Wiener index and Pielou evenness index of cut-over land were significantly lower than that of sprout forest（P〈0.05）,and there were no significant differences between the other parts.The composition of plant species was significant differences in three communities.Canopy light-transmittance coefficient,soil porosity,slope direction and soil available phosphorus were important influences on species distribution pattern in shrub layer.Superposition effects of 4environmental factors explained 90%of variation of 3kinds of communities of shrub layer species composition.Canopy light-transmittance coefficient,slope direction,total nitrogen/total phosphorus,available nitrogen/available phosphorus and soil porosity were important influences on herb layer species distribution patter.Superposition effects of 5environmental factors explained the 86% of variation of herb layer species composition between 3co