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水生-陆地系统补贴形成的联结作用在构建群落和调节生态系统功能方面发挥重要作用.在营养贫瘠的生态系统中(例如密歇根湖周围的淡水沙丘),水生-陆生系统补贴显得尤为重要.春季成年蠓在密歇根湖涌出,成群交配,然后死亡.蠓尸体在植物的基部形成土丘状,通过输入营养提高植物的生产力.然而,水生-陆地系统补贴对植物生产力的影响可能取决于其他生物的交互作用,特别是土壤微生物可能通过促进养分转化为植物可利用的形式或与植物竞争养分而发挥关键作用.在温室实验中,我们检验了湖生蠓(Chironomidae)的尸体和土壤微生物如何独立和相互影响一种常见沙丘草(沙拂子茅,Calamovilfa longifolia)的生长表现.为确定蠓是否影响土壤非生物特性,我们检验了添加蠓如何影响土壤养分和土壤湿度.研究结果显示,蠓极大地增加了植物生物量,但其效应的大小受土壤微生物的影响.在没有土壤微生物的情况下,添加蠓的植物生物量比没有添加的高7倍,而在有土壤微生物的情况下,植物生物量提高了3倍.蠓对植物生长的促进作用可能由于它们向土壤中输入养分所导致,因为与沙丘土壤相比,蠓的氮、磷、钾含量分别高100倍、10倍和150倍.我们的研究结果表明,土壤微生物可能与植物竞争这些养分.总之,我们发现蠓是重要的水生-陆地系统补贴,对密歇根湖沿岸植物生产力产生强烈和正向的影响,但水生-陆地系统补贴作用必须在生态群落内发生的复杂相互作用的背景下考虑.“,”Aims Linkages formed through aquatic-terrestrial subsidies can play an important role in structuring communities and mediating ecosystem functions.Aquatic-terrestrial subsidies may be especially important in nutrient-poor ecosystems,such as the freshwater sand dunes surrounding Lake Michigan.Adult midges emerge from Lake Michigan in the spring,swarm to mate and die.Their carcasses form mounds at the base of plants,where they may increase plant productivity through their nutrient inputs.However,the effect of aquatic-terrestrial subsidies on plant productivity could depend on other biotic interactions.In particular,soil microbes might play a key role in facilitating the conversion of nutrients to plant-available forms or competing for the nutrients with plants.Methods In a greenhouse experiment,we tested how carcasses from lake emergent midges (Chironomidae) and soil microbes independently and interactively influenced the performance of a common dune grass,Calamovilfa Iongifolia.To determine whether midges influenced abiotic soil properties,we measured how midge additions influenced soil nutrients and soil moisture.Important Findings Midges greatly increased plant biomass,while soil microbes influenced the magnitude of this effect.In the absence of soil microbes plant biomass was seven times greater with midges than without midges.However,in the presence of soil microbes,plant biomass was only three times greater.The effect of midges might be driven by their nutrient inputs into the soil,as midges contained 100 times more N,10 times more P and 150 times more K than dune soils did.Our results suggest that soil microbes may be competing with plants for these nutrients.In sum,we found that midges can be an important aquatic-terrestrial subsidy that produces strong,positive effects on plant productivity along the shorelines of Lake Michigan,but that the impact of aquatic-terrestrial subsidies must be considered within the context of the complex interactions that take place within ecological communities.