三江源地区人工克隆植物群落生物多样性对初级生产力的影响及机制

Effects of biodiversity on primary productivity and its mechanism in artificially sown clonal plant communities of the Sanjiangyuan region

克隆植物具有独特的竞争和繁殖方式,这可能会使其构建的群落呈现不一样的生物多样性-生态系统功能关系,但是本议题却极少被研究。本研究利用垂穗披碱草、花苜蓿和鹅绒委陵菜构建了一个生物多样性试验,并将单播和混播重复3次,且将垂穗披碱草作为所有混播的固定物种,以此跨越两个生长季测试生物多样性对生产力的影响。本研究发现,物种丰富度和地上生物量之间并没有线性正相关关系,但是大多数混播的净多样性效应(NE)都是显著的,且NE主要来源于非特征依赖性互补效应(TICE)。较强的TICE主要来自地上垂直空间的互补性利用;其次来自底层物种鹅绒委陵菜光吸收能力的增强。沿着时间和物种丰富度梯度,垂穗披碱草的优势度增强,鹅绒委陵菜的优势度下降,致使特征依赖型互补效应(TDCE)和优势度效应(DE)随之增强,但是它们对NE的贡献有限。另外,以上3种效应均随时间增强。总之,本研究的结果表明克隆植物群落表现出了不一样的多样性-生产力关系模式,并且这种多样性效应主要来自地上垂直空间的互补性利用。

Clonal plants have unique ways to compete and reproduce,and their unique traits may lead to a particular biodiversity-productivity relationship in communities they form.However,this issue has rarely been studied.In this research,a biodiversity experiment was set up using three clonal species(Elymus nutans,Medicago ruthenica and Potentilla anserine)in monocultures and mixtures.There were three replicates,E.nutans was used as the fixed species in all mixtures and the effects of biodiversity on productivity were assessed over two years.We found that the net biodiversity effects(NE)were significant in nearly all mixtures in our experiment,attributable to strong traitindependent complementary effects(TICE),although there was no positive linear relationship between species richness and aboveground biomass.The strong TICE was predominantly caused by the complementary utilization of aboveground vertical space,while a secondary cause was the enhancement of light absorption capacity of the understorey species P.anserine.Meanwhile,the dominance of E.nutans increased over time and with increasing species richness,whereas P.anserine displayed the opposite tendencies,resulting in an increase in trait-dependent complementary effect(TDCE)and dominance effect(DE)for communities where P.anserine was present.However,the contributions of those two mechanisms to NE were limited.Furthermore,all those effects increased with time.The results of this study indicate that clonal species display a different biodiversity-productivity relationship from the normally positive linear pattern,due to the complementary use of aboveground vertical space.