Anthropogenic activities are dramatically altering patterns of biodiversity around the globe,triggering extensive research on the consequences of changes in biodiversity of ecosystem and community processes.Multiple investigations on the ecological effects of both plant genetics and species diversity have shown,for example,that more diverse systems are generally more productive,and support more abundant and more diverse animal communities.In recent years,some research have shown showed that the outcome of plant-plant interactions varies with the diversity of dominant neighbor genotypes.Plant diversity,either genotypic or species diversity,could mediate plant-plant interactions in communities via at least two mechanisms.First,increased relative competition intensity between neighboring plants and target species typically leads to higher productivity of neighboring plants.Alternatively,increased trait variation of neighboring plants rather than increased competition in different communities may explain the change in plant-plant interactions.In the present study,we hypothesized that genotypic diversity of the neighboring plants may affect the growth of the target species by changing the coefficient of trait variation of the community.In this study,we conducted a factorial microcosm experiment with three combinations of genotypes (1,3,6 genotypes =G1,G3,G6) of two neighboring plants (Leymus chinensis and Koeleria cristata),and one genotype of the target species,Artemisia frigida.Furthermore,we investigated the growth performance (aboveground biomass,belowground biomass,total biomass,and plant height) and relative competition intensity (RCI) of A.frigida when surrounded by different levels of genetic diversity for L.chinensis or K.cristata.We analyzed six traits (aboveground biomass,belowground biomass,total biomass,plant height,root length,and specific leaf area [SLA]) of L.chinensis or K.cristata at different levels of genotypic diversity using principal component analysis (PCA).In addition,the correlations between the four traits of A.frigida and six traits of L.chinensis or K.cristata were calculated by means of Kendall rank correlation coefficient analysis.The results revealed the following:(1) The performance of A.frigida was dependent on neighboring plants.Higherg genotypic diversity of L.chinensis significantly decreased aboveground biomass,total biomass and plant height of A.frigida,and A.frigida grew the least when the genotype number of L.chinensis was six.For G6 of L.chinensis,the RCI of aboveground,belowground and total A.frigida was significantly greater than that for the G1 treatment (P＜0.05).However,for K.cristata,genotypic diversity did not exhibit significant effects on the performance or RCI of A.frigida.(2) The trait variation of neighboring plants was also dependent on the species and their genotypic diversity.When the neighboring plant was L.chinensis,genotypic diversity significantly affected trait variation,and trait variation increased with an increasing number of genotypes,whereas no significant differences were detected when the neighboring plant was K.cristata.(3) The results of the Kendall correlation coefficient analysis revealed significant negative correlations between total biomass and SLA of L.chinensis and aboveground biomass and total biomass of A.frigida.These results provided experimental data on the effects of genotypic diversity of neighboring plants on the target species,and we outlined how more traits or relative competition intensity mediating plant-plant interactions could be identified.Future studies may use population genetic survey of genotype distribution in fields and methods from trait-based ecology to better quantify the impact of intraspecific genetic variation on plant-plant interactions,so as to facilitate and enhance ecological restoration in the typical steppe of northern China in the context of global change.%植物物种多样性与基因型多样性对群落的结构和功能具有重要的生态作用,近年来植物基因型多样性对植物间相互作用的影响已成为研究者关心的重要科学问题.实验选择退化草原优势种冷蒿(Artemisia frigida)为目标植物,稳定群落建群种羊草(Leymus chinensis)和群落伴生种洽草(Koeleria cristata)为邻居植物,来研究基因型多样性不同的邻居植物对冷蒿生长表现(株高、地上生物量、地下生物量和总生物量)的影响,并通过测量植物相对竞争强度及邻居植物性状变异来进一步探究邻居植物基因型多样性对目标植物影响的内在机制.结果表明:(1)邻居物种为羊草时,基因型多样性对冷蒿的生长表现影响显著,当邻居为6基因型时,冷蒿的株高、地上生物量以及总生物量显著低于单基因型和3基因型时的表现(P＜0.05),且相对竞争强度高于其他两种处理;而邻居物种为洽草时,基因型多样性对冷蒿所有观测指标以及相对竞争强度的影响均不显著(P＞0.05).(2)利用主成分分析法来分析基因型多样性对自身性状变异的影响发现,邻居物种为羊草时,基因型多样性对性状变异响应显著,主要表现为3基因型时,羊草种群的株高、总生物量、地上生物量显著高于单基因型时的表现(P＜0.05);而邻居物种为洽草时,基因型多样性对性状变异影响不显著(P＞0.05).(3)邻居物种为羊草时,羊草总生物量和比叶面积与冷蒿的地上生物量和总生物量呈显著负相关(P＜0.05);邻居物种为洽草时,洽草各性状与冷蒿性状间无显著相关性(P＞0.05).实验结果揭示,基因型多样性对目标植物生长的效应受邻居植物种类的影响,稳定群落建群种羊草高基因型组合能显著抑制冷蒿的生长,这可能与羊草高基因型多样性种群性状变异大且对冷蒿有较高的相对竞争强度有关.所得结果为建群种基因型多样性影响种间相互作用提供了实验证据,为草原的合理利用和保护提供了理论指导.
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