Himalayan balsam (Impatiens glandulifera) is a highly invasive annual herb that has become extremely prevalent in riparian zones across the UK. The competitive ability of I. glandulifera, both in terms of resource exploitation and allelopathy (i.e., the release of biochemicals that may be toxic to neighbouring plants), is considered a key determinant of its success. Little is known, however, about the effects of the resident community on the establishment and growth of I. glandulifera. Here, we aim to increase our understanding of the competitive ability of this highly invasive plant by investigating the effects of soil conditioning on the performance of four co-occurring native species (Tanacetum vulgare, Urtica dioica, Chelidonium majus and Arabidopsis thaliana). In addition, we also aim to investigate the effect that the pre-existing species composition have on the performance of I. glandulifera seedlings by establishing artificial communities (monocultures and mixtures of four UK native species, including U. dioica). We found negative effects of soil conditioning by I. glandulifera in all four species, either by reducing above-ground biomass, chlorophyll content or both. Monocultures of U. dioica were the only artificial communities that reduced growth of I. glandulifera, and we did not find any support for the idea that a more diverse community may be more resistant to invasion. Our results confirm the high competitive ability of I. glandulifera and highlight how the identity of the natives in the resident community may be key to limit its success.

喜马拉雅苦瓜（Impatiens glandulifera）是一种具有高度侵入性的一年生草本植物，在英国的河岸地区极为流行。在资源开发和化感作用（即释放可能对邻近植物有毒的生化物质）方面，I。glandulifera的竞争能力被认为是其成功的关键因素。然而，关于居民社区对兰氏肠杆菌的建立和生长的影响知之甚少。在这里，我们旨在通过研究土壤调节对四种同时出现的本地物种（艾美acet，荨麻叶Ur）的性能的影响，从而加深对这种高入侵植物竞争能力的了解。，白屈菜和拟南芥）。此外，我们还旨在通过建立人工群落（单一培养物和包括U. dioica在内的四种英国本土物种的混合物）来调查预先存在的物种组成对兰I. glandulifera幼苗性能的影响。我们发现，通过降低地上生物量，叶绿素含量或同时降低这两者，甘兰I. glandulifera对土壤条件的负面影响。唯一的U. dioica人工养殖群落减少了I. glandulifera的生长，并且我们没有发现支持更多样化的社区可能更抵御入侵的想法。我们的结果证实了I. glandulifera的高竞争能力，并强调了居民社区中本地人的身份可能是限制其成功的关键。