In island ecosystems, biological invasions are one of the major threats to native biodiversity and to ecosystem functioning. Invasive ornamental plants such as the alien palm tree Pinanga coronata in the Fiji islands can form mono‐dominant stands in rainforests and displace native species. Using a functional trait‐based approach, we investigated the impact of P. coronata on both above and belowground communities (i.e. plants and Collembola). Within a rainforest reserve on Fiji´s principal island, we sampled a total of 10 invaded and non‐invaded plots and recorded five functional traits for plants and six for Collembola. We found that invasion by P. coronata led to a strong and significant decrease of native plants and Collembola taxonomic diversity. Ingress of P. coronata also induced a decrease in the functional diversity of plant communities and to a lesser extent of Collembola communities. P. coronata invasion led to a decrease of leaf carbon–nitrogen ratio (LCN), Leaf nitrogen content (LN), specific leaf area (SLA) and leaf dry matter content (LDMC) of plant communities, suggesting a change in litter properties compared to non‐invaded communities. Plots with P. coronata were associated with large Collembola living at the soil surface with more trichobothria and pseudocelli, which are used as defence mechanisms. Using trait‐matching, we also found that the strength of plant‐soil relationships was higher (i.e. more stable) in non‐invaded plots than in P. coronata‐invaded plots. Lastly this study suggests that the main mechanism through which P. coronata alters soil communities is a change in plant properties rather than a change in the abiotic environment. Our trait‐based approach underlines the negative impact of this alien palm invasion on native rainforest plant and soil fauna in Fiji, and the urgent need for on‐the‐ground action to conserve terrestrial island biodiversity in Fiji´s rainforests.

中文翻译：

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一种基于功能性状的方法，用于评估外来棕榈入侵对南太平洋岛屿上植物和土壤群落的影响

在岛屿生态系统中，生物入侵是对本地生物多样性和生态系统功能的主要威胁之一。入侵的观赏植物，例如斐济群岛上的外来棕榈树Pinanga coronata，可以在热带雨林中形成单一优势的林分，并取代本地物种。使用基于功能性状的方法，我们调查了冠脉假单胞菌对地上和地下社区（即植物和Collembola）的影响。在斐济主要岛屿的热带雨林保护区内，我们对10个入侵和非入侵样地进行了采样，并记录了植物的5个功能性状和Collembola的6个性状。我们发现冠状腐霉入侵导致本地植物和Collembola分类学多样性大幅下降。冠脉假单胞菌的入侵也引起植物群落功能多样性的降低，而Collembola群落的程度降低。冠脉假单胞菌入侵导致植物群落叶片碳氮比（LCN），叶片氮含量（LN），比叶面积（SLA）和叶片干物质含量（LDMC）降低，表明凋落物特性相比有所变化到非入侵社区。P. coronata的情节它们与生活在土壤表层的大型Collembola有关，并具有更多的毛滴虫和假细胞，它们被用作防御机制。使用特征匹配，我们还发现，植物-土壤关系的力量在非侵入地块更高（即更稳定）比P. coronata -invaded地块。最后，这项研究表明，冠日疟原虫改变土壤群落的主要机制是植物特性的改变而不是非生物环境的改变。我们基于特征的方法强调了外来棕榈入侵对斐济本地雨林植物和土壤动物的负面影响，以及迫切需要采取地面行动来保护斐济雨林中的陆地岛屿生物多样性。