氮沉降对外来种豚草入侵能力与竞争能力的影响

通过温室控制实验,模拟不同的氮沉降量对外来种豚草和本地种黄花蒿、蒙古蒿形态、生物量及其分配以及种间竞争的影响。结果表明:外来种豚草对氮素变化表现出很高的可塑性,而本地种可塑性不高。随氮素的增加,豚草的株高、基茎、总生物量、支持结构生物量比显著增加,根生物量比、根冠比明显降低;本地种除株高、根冠比等少数指标外,多数指标无显著差异。氮沉降有利于外来种豚草在种间竞争中取得优势。豚草和黄花蒿的混栽试验显示,随着氮水平的增加,豚草的竞争力加强,在竞争中取得了优势;豚草和蒙古蒿的混栽试验显示,低氮量下蒙古蒿具有一定的竞争优势,高氮量下竞争优势减弱。全球变化造成氮沉降的增加有利于外来入侵植物的生长与竞争。

Effects of Nitrogen Deposition on Invasive and Competitive Abilities of an Alien Plant Ambrosia artemisiifolia

An experiment was conducted to study the effects of nitrogen deposition on morphological indices,biomass and its allocation,and interspecies competition of an invasive plant Ambrosia artemisiifolia(common ragweed) and two native plants Artemisia annua and Artemisia mongolica.Results show that the invasive species is more plastic in response to nitrogen availability,compared with the two native species.With increasing nitrogen levels,the plant height,basal diameter,total biomass,supporting organs mass ratio(SMR) of the invasive species significantly increased,while root biomass ratio(RMR) and root-to-shoot ratio decreased obviously.Nitrogen deposition had no significant effects on the morphological indices,biomass and its allocation of the native species except plant height and root-to-shoot ratio.Nitrogen deposition was beneficial for the invasive species to gain advantage in interspecies competition.The competitive ability of the invasive species enhanced with increasing nitrogen levels when mixed planting with Artemisia annua;however,A.mongolica was more competitive than A.artemisiifolia under low nitrogen levels,and less competition of A.artemisiifolia was observed under high nitrogen levels when mixed planting with A.mongolica.The results show that nitrogen deposition is in favor of the invasive species,resulting in a wide dispersal of A.artemisiifolia in Beijing region.