模拟氮沉降对外来入侵植物互花米草生长及化感作用的影响

Effects of simulated nitrogen deposition on seedling growth and allelopathic potential of exotic invasion Spartina alterniflora

通过设置室内模拟实验,从生长特性和化感作用的角度,探讨了氮沉降对外来入侵植物互花米草入侵潜力的影响。结果表明,低氮沉降和高氮沉降处理都明显促进了互花米草地上和地下部的生物量累积,其中低高氮沉降分别使地上部生物量增加161.15%和120.20%,使地下部生物量增加128.43%和71.06%。而氮沉降使叶面积和叶重也显著增加,这将增强其对资源的捕获和利用能力。而不同氮沉降处理下互花米草的叶、根水浸液对莴苣种子萌发和幼根生长具有化感抑制作用,当浸提液浓度相同时,低氮沉降比其他氮处理有更强的综合化感效应。互花米草叶和根的综合化感效应分别在低氮沉降处理下浸提液浓度为0.02 g·m L^(–1)和0.04 g·m L^(–1)时最大。高氮沉降处理下互花米草各项指标并不完全优于低氮沉降处理,这可能由于高氮沉降处理下其生长已不处于氮限制状态。全球氮沉降是一个漫长的过程,在目前的氮沉降条件下,加强对互花米草的防治和管理迫在眉睫。

Nitrogen deposition is one of the hot topics of global climate changes. In this study, effects of simulated nitrogen deposition with three different levels on the seedling growth and allelopathic potential of exotic invasion plant Spartina alterniflora were evaluated in laboratory. The results showed that both low and high concentration of nitrogen deposition significantly increased the biomass accumulation of the above-ground and below-ground parts of S. alterniflora. Its above-ground biomass under the two nitrogen deposition treatments was increased by 161.15% and 120.20%, respectively. And the below-ground biomass was increased by 128.43% and 71.06%, respectively. The leaf area and leaf weight were also increased by nitrogen deposition treatment, which would promote S. alterniflora to enhance the ability of resource capture and utilization. The water extracts of the roots and leaves of S. alterniflora under different nitrogen deposition treatments inhibited the seed germination rate and root length of Lactuca sativa. At the same concentrations of water extracts, the synthetic allelopathic effects of S. alterniflora under the low nitrogen deposition treatment were always stronger than those under high nitrogen deposition treatment and no nitrogen application. The synthetic allelopathic effects of leaves and roots reached the maximum when their water extract concentrations were 0.02 g·m L^（-1） and 0.04 g·m L^（-1） respectively under the low nitrogen deposition treatment. The above-mentioned measurement records of S. alterniflora under the high nitrogen deposition were not altogether superior to those under low nitrogen deposition, which may suggest that S. alterniflora growing under the high nitrogen deposition level would not be in nitrogen limited condition. As global nitrogen deposition elevation is a gradual process, ecological control and management of S. alterniflora will be more urgent under present nitrogen deposition condition.