中文摘要：

在东北羊草草地上，采用模拟不同梯度凋落物层，探讨凋落物层对植物群落特征的影响。结果表明，随着凋落物积累量的增加，群落种类组成、优势种的数量特征、生物量，呈连续变化的趋势。群落物种数目随着凋落物层厚度增加而增多，于800g／m^2处达到最大值，然后随厚度增加种数逐渐减少。羊草种群的密度、高度、盖度呈先增后降的趋势，最大值出现在600g／m^2处。地上部和地下部生物量的变化曲线呈抛物线型，峰值分别出现在600g／m^2和700g／m^2处。凋落物积累量的最佳范围为600～700g／m^2之间，在此范围内植物群落可良好的发育。

英文摘要：

In this paper, we simulated different levels of litter to discuss influences of litter layer on the community of Leymus chinensis in northeastern grassland of China. The results indicated that composition, dominant species and biomass were changed with the varying of litter accumulation. The species increased with the increasing of litter and were most abundant at 800 g/m^2 litter. It decreased where litter layer was more than 800 g/m^2. The population density, height and coverage increased with the increasing of litter and reached their peaks at 600 g/m^2 litter, which decreased where litter layer was more than 600 g/m^2. Both aboveground biomass and underground biomass showed ＂parabola＂ curve, of which the peaks presented at 600 g/m^2 and 700 g/m^2 litter, respectively. The optimal accumulation of litter was in the scope between 600 and 700 g/m^2, in which the Leymus chinensis community developed best.