中文摘要：

为研究林分结构对林下植物特征的影响，对江苏省泗洪陈圩林场南林95杨（Pop—ulus xeuramericanaCV．“Nanlin-95”）4种不同结构的林分林下植物进行了调查。结果表明：低密度杨树林分林下植物的Shannon指数高于高密度林分，而高密度林分林下植物Pielou均匀度指数较高，分布较均匀；低密度杨树林分林下植物生物量高于高密度林分，低密度林分的林下植物具有较高的N、P、K、Mg养分浓度和累积量，但ca的浓度和累积量在不同林分结构下差异不大；林下植物5月的N、P、Ca浓度和累积量大于11月，而K、Mg则小于11月。

英文摘要：

Poplar （ Nanlin-95 ） plantations with different stand densities and spacing were investi- gated to study the effects of stand structure on understory characteristics in Chenwei Forest Farm, Sihong County, Jiangsu Province. The results showed that the Shannon index of the understory was higher under the low density stands than under the high density ones, while the distribution of understory was much homogeneous under high density stands, with a higher Pielou evenness index. The diversity index of the understory was lower in May than in November. The biomass of the understory was higher in the low density stands than in the high density stands. Low stand densities increased the concentration and accumulation of N, P, K, and Mg in understory, while no significant effects of stand structure were detected on the concentration and accumulation of Ca in understory. The concentration and accumulation of N, P, and Ca were higher in May than in November while the concentration and accumulation of K and Mg were lower in May than in No- vember.