基因型多样性对羊草种群年龄结构的影响

基因型多样性作为遗传多样性的重要组成部分，不仅在群落水平，而且在种群水平均可以发挥重要生态作用。以羊草（Leymus chinensis）为研究对象，设置5种基因型多样性梯度试验控制小区，进行基因型多样性对羊草种群年龄结构的影响研究。结果表明：随基因型多样性梯度的逐步增加，2a分蘖株生物量和数量均显著增加（P<0.05）；1-4龄级羊草根茎生物量、长度和干物质积累量多数呈极显著性增加的变化趋势（P<0.01）。在1、2、4、8和12种基因型多样性梯度时，分蘖株生物量及数量年龄结构均以1a或2a分蘖株所占比例为最高，年龄结构表现为增长型或稳定型；而羊草种群根茎生物量和长度也以2a根茎所占比例为最高，年龄结构表现为稳定型。随基因型多样性水平的增加，羊草种群分蘖株数量和生物量的年龄结构从增长型向稳定型过渡，但根茎长度和生物量的年龄结构均为稳定型。12基因型多样性水平的4龄级分蘖株和根茎的特征高于其他基因型多样性水平。因此，在不同基因型多样性水平羊草种群分蘖株和根茎具有增长型或稳定型的年龄结构，适当的基因型多样性数量显著促进了各龄级羊草分蘖株和根茎的生物量和数量特征的升高，但高度的基因型多样性水平会增加羊草种群中高龄级的分蘖株和根茎所占的比例，种群发展表现出衰退信号。

Effects of genotypic diversity on age structure in Leymus chinensis population

Genotypic diversity is an important part of biodiversity, which plays an important ecological role not only at the community level, but also at the population level. In this study, we set up five gradients of genotypic diversity to explore the effects of genotypic diversity on Leymus chinensis population from the perspective of age structure. The results showed that the biomass and number of 2nd age class tillers of L. chinensis population increased significantly with the increase of genotypic diversity (P<0.05),and the biomass of rhizome,length and dry matter accumulation of L. chinensis in different ages increased significantly (P<0.01). At five gradients of genotypic diversity,percentage of biomass and tiller number of 1st or 2nd age class tillers were the highest among different ages and showed expanding or stable age structure. But percentage of rhizome length and biomass in L. chinensis population of 2nd age rhizomes were highest proportion among different ages and showed stable age structure. With the increase of genotypic diversity,the age structure of tiller number and biomass of L. chinensis population transited from expanding type to stable type,but the age structure of rhizome length and biomass were stable type. The characteristics of tillers and rhizomes at age 4th of 12 genotypic diversity level were higher than other genotypes. The cumulative length of the rhizome of L. chinensis not only reflects the asexual reproduction ability, but also reflects its spatial expansion ability. High genotypic diversity significantly increases the length of the rhizome of L. chinensis population. The reason is that genotypic diversity can improve the soil nutrient absorption efficiency of L. chinensis, thus effectively promoting the root growth and providing conditions for population expansion. Therefore,the tillers and rhizomes of L. chinensis population have an expanding or stable age structure at different genotypic diversity levels. Moderate genotype number promotes the increase of the biomass and number characteristics of tillers and rhizomes at different age levels. This is due to the contribution of complementary effect to the positive effect of genotypic diversity. There are some differences in morphological and physiological characteristics among different genotypic levels of L. chinensis, resulting in different nutrient requirements and resource utilization ability of different genotype of L. chinensis. The increase of genotypic diversity can improve the utilization rate of resources and promote the development of L.chinensis population.However, over high genotypic diversity will increase the proportion of senior tillers and rhi senior zomes in the population of L. chinensis,and the development of population showed a decline signal.