中文摘要：

以嫩江沙地樟子松防风固沙人工林为对象,调查不同发育阶段（24、29、39和43年生）林分的种群结构、林下物种组成以及多样性的变化.结果表明：研究期间,所有樟子松人工固沙林中均未见更新幼苗.不同发育阶段的樟子松人工林在胸径和高度上有显著差异,随着林龄的增加,小径级个体的比例明显降低,大径级个体增多,种群趋于成熟,径级结构除43年生外均呈正态分布.林下物种共计33种,隶属于15科28属,禾本科的狗尾草为林下草本植被的优势种,但其优势程度随林龄增加而逐渐减小;随着林龄的增加,1年生植物的比例减少,多年生植物比例增加;Simpson多样性指数与Pielou均匀度指数差异不显著,39年生樟子松的丰富度指数、Shannon多样性指数和Alatalo均匀度指数均显著高于24年生樟子松,群落的物种多样性有所改善.

英文摘要：

Taking the Pinus sylvestris var.mongolica sand-fixing plantations at different development stages（24-,29-,39-,and 43 years old） in Nenjiang Sandy Land as test objects,this paper studied their population structure,understory species composition,and species diversity.No regenerated seedlings were found in all the four P.sylvestris var.mongolica plantations.The mean individual height and DBH of the populations differed significantly with development stage.With the increasing age of the plantations,the proportion of small-sized individuals decreased obviously,while that of large-sized individuals increased,population tended to mature,and the diameter structure except 43 years old plantation was in normal distribution.A total of 33 understory plant species were recorded,belonging to 28 genera and 15 families.Setaria viridis was the dominant species,but its dominance decreased gradually with increasing age of the plantations.With the increase of plantation age,the proportion of annual plants decreased,while that of perennial plants increased.The Simpson index and Pielou index had no significant differences among the different aged plantations,but the richness index,Shannon index,and Alatalo index of 39 years old plantation were significantly higher than those of 24 years old stands,suggesting that the species diversity of the community improved with time.