Despite good recognition of distributions and spread mechanisms of the three most invasive trees in Europe (Prunus serotina, Quercus rubra and Robinia pseudoacacia), their impacts on forest biodiversity are unevenly recognized. Most studies cover only taxonomic alpha diversity, and only a single study included functional and phylogenetic diversity. Using a set of 186 study plots in western Poland we assessed the impacts of these invasive tree species on the alpha and beta taxonomic, functional and phylogenetic diversity of understory vascular plants. Alpha diversity was higher in R. pseudoacacia forests and lower in Q. rubra forests compared to mature native forests. Compared to non-invaded plantations and forests, alpha diversity was higher in P. sylvestris plantations invaded by P. serotina, but lower in invaded nutrient-poor P. sylvestris forests. Alien species richness was higher and beta diversity was lower in forests invaded by P. serotina or R. pseudoacacia than in non-invaded forests. In contrast, beta diversity was higher in Q. rubra forests than in native forests. We proved that invaded forests differed from non-invaded forests in species composition, but not always with decreased alpha and beta diversity. Impacts of particular invasive species also depended on the reference ecosystem properties (here mature native forests, which did not always have the highest biodiversity), which is a source of inconsistency in previous studies, usually referring to single native ecosystem types.

尽管人们已经很好地认识到欧洲三种入侵性最强的树木（李子，欧洲栎和刺槐）的分布和传播机制，但它们对森林生物多样性的影响却没有得到公认。大多数研究仅涵盖生物分类学的α多样性，只有一项研究包括功能和系统发育多样性。我们使用波兰西部的186个研究区来评估这些入侵树种对林下维管植物的alpha和beta分类学，功能和系统发育多样性的影响。R. pseudoacacia森林中的阿尔法多样性较高，而Q. rubra中的较低森林与成熟的原生森林相比。相比于非侵入种植园和森林，阿尔法多样性明显高于P.樟子松人工林草入侵P.酸橙木，但在入侵贫瘠降低P.樟子松林。外来物种丰富度更高和β多样性较低森林入侵由P.酸橙木或刺槐比非侵入森林。相比之下，β多样性较高的Q.杨梅森林要比原生森林要大。我们证明了入侵森林的物种组成与非入侵森林不同，但并非总是具有降低的alpha和beta多样性。特定入侵物种的影响还取决于参考的生态系统特性（此处是成熟的原生林，不一定总是具有最高的生物多样性），这是以前研究中不一致的根源，通常是指单一原生生态系统类型。