中文摘要：

对永安市不同经营密度下尾赤桉（Eucalyptusurophylta×Eeamakchucensis）人工林的林分结构、群落组成以及林下枯落物和土壤持水性能进行了分析，探讨造林密度对闽西北地区桉树人工林生态效应的影响。结果表明，密度对尾赤桉人工林林分径级结构有极显著影响，密度与平均胸径、树高间存在极显著的负相关，相关系数分别为-0．99和-0．93，对林分蓄积量也存在显著影响（r=0．84）。密度对林下灌草层物种多样性的影响呈现分异现象，与灌木层的相关性达到极显著水平（r=0．94），但与草本层的相关不显著（r=-0．52）。不同密度林分的林下植物种类有较大差异，但低密度林分的林下植被收获量最大。林分密度对枯落物持水率的影响较（r==0．94）。

英文摘要：

The community structure and water holding capacity of litter and soil of Eucalyptus urophylta ×E. econalducensis plantations under different management densities in Yong＇an City were studied. The results showed that the management density obviously affected the plantation structure, which had significant correlations to DHB and tree height, with correlation coefficient of-0.99 and-0.93, respectively, and that to stand volume with r = 0.84. The effects of densities on species diversities from shrub layer to herb layer were different, which had significant correlation to shrub layer with r=0.94, and poor correlation to herb layer with r =-0.52. The species composition of undergrowth layer were great different under 5 different densities, and the vegetation yield under low density was the biggest. The litter maximum water holding capacity had significant correlation to stand densities with r=0.94.