中文摘要：

基于4种密度羊草种群的温室模拟试验，分析了羊草种群地上生物量与地下生物量的动态变化．结果表明：羊草种群的地上生物量与地下生物量随生长期呈增加的趋势，且随密度的增加而增加，但不同密度间羊草地上生物量与地下生物量的相对生长速率没有显著差异；不同密度羊草种群的根冠比随生长进程而增加，但差异不显著，表明环境因子是影响羊草种群根冠比变化的主导因素；单株羊草及羊草种群的地上生物量和地下生物量间存在显著的幂函数关系，但幂函数指数与系数随羊草密度的变化而变化，表明资源竞争引起的微环境差异导致了羊草种群根冠比的动态变化，可为定量研究光合产物分配提供参考．

英文摘要：

Based on a greenhouse simulation experiment, this paper studied the dynamics of the above- and below-ground biomass of Leymus chinensis populations with four planting densities （120, 240, 360 and 480 plants · m^-2）. The results showed that the above- and below-ground biomass of L. chinensis populations had an increasing trend with the growth, and increased with increasing planting density. However, the relative growth rates （RGRs） of the above- and below-ground biomass did not show significant difference among the L. chinensis populations. The ratio of root to shoot （RRS） of the L. chinensis populations increased with their growth, but did not show significant difference among the planting densities, implying that environmental factors were the controlling factors for RRS. There existed significant power function relationships between the above- and below-ground biomass of L. chinensis individuals and populations, but the power function indices and coefficients varied with the planting density. It was suggested that the difference of microenvironment resulted from resources competition could induce the changes of L. chinensis RRS, and the latter could be used as a reference to quantitatively study the allocation of photosynthetic products.