Intact tropical rainforests are considered robust to plant invasions. However, land-use change alters the structure and species composition of native forest, opening up tropical landscapes to invasion. Yet, the relative roles of key drivers on tropical forest invasions remain little investigated. We examine factors affecting plant invasion of rainforest remnants in oil-palm dominated landscapes in Sabah, Malaysian Borneo. We hypothesized that invasion is greater in highly fragmented landscapes, and in disturbed forests with lower native plant diversity (cf. old-growth rainforests). Native and exotic plants were surveyed in 47 plots at 17 forest sites, spanning gradients in landscape-scale fragmentation and local forest disturbance. Using partial least squares path-modelling, we examined correlations between invasion, fragmentation, forest disturbance, propagule pressure, soil characteristics and native plant community. We recorded 6999 individuals from 329 genera in total, including eight exotic species (0–51% of individuals/plot, median = 1.4%) representing shrubs, forbs, graminoids and climbers. The best model (R2 = 0.343) revealed that invasion was correlated with disturbance and propagule pressure (high prevalence of exotic species in plantation matrix), the latter being driven by greater fragmentation of the landscape. Our models revealed a significant negative correlation between invasion and native tree seedlings and sapling community diversity. Increasing landscape fragmentation promotes exotic plant invasion in remnant tropical forests, especially if local disturbance is high. The association between exotic species invasion and young native tree community may have impacts for regeneration given that fragmentation is predicted to increase and so plant invasion may become more prevalent.

中文翻译：

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土地利用变化和繁殖压力促进热带雨林残余物中的植物入侵

完整的热带雨林被认为可以抵御植物入侵。然而，土地利用的变化改变了原生森林的结构和物种组成，为入侵打开了热带景观。然而，关键驱动因素对热带森林入侵的相对作用仍然很少被调查。我们研究了影响植物入侵马来西亚婆罗洲沙巴油棕主导景观中雨林残余物的因素。我们假设，在高度分散的景观中，以及在原生植物多样性较低的受干扰森林（参见古老的雨林）中，入侵更大。在 17 个森林地点的 47 个地块中对本地和外来植物进行了调查，跨越了景观尺度破碎和当地森林干扰的梯度。使用偏最小二乘路径建模，我们检查了入侵、分裂、森林干扰、繁殖压力、土壤特征和本地植物群落。我们总共记录了 329 个属的 6999 个个体，包括代表灌木、杂草、禾本科和攀缘植物的 8 个外来物种（个体/地块的 0-51%，中位数 = 1.4%）。最好的模型 (R2 = 0.343) 显示入侵与干扰和繁殖压力（种植园基质中外来物种的高流行率）相关，后者是由更大的景观碎片驱动的。我们的模型揭示了入侵与本地树苗和树苗群落多样性之间的显着负相关。不断增加的景观破碎化促进了剩余热带森林中外来植物的入侵，尤其是在局部干扰严重的情况下。