Temporal fluctuation in nutrient availability generally promotes the growth of exotic plant species and has been recognized as an important driver of exotic plant invasions. However, little is known about how the impact of fluctuating nutrients on exotic species is dependent on the availability of other resources, although most ecosystems are experiencing dramatic variations in a wide variety of resources due to global change and human disturbance. Here, we explored how water availability mediates the effect of nutrient pulses on the growth of six exotic and six native plant species. We subjected individual plants of exotic and native species to well watered or water stressed conditions. For each level of water availability, we added equivalent amounts of nutrients at a constant rate, as a single large pulse, or in multiple small pulses. Under well watered conditions, nutrient pulses promoted exotic plant growth relative to nutrients supplied constantly, while they had no significant effect on natives. In contrast, under water stressed conditions, water deficiency inhibited the growth of all exotic and native species. More importantly, nutrient pulses did not increase plant growth relative to nutrients supplied constantly and these phenomena were observed for both exotic and native species. Taken together, our study shows that the impact of fluctuating nutrient availability on the growth of exotic plant species strongly depends on the variation of other resources, and that the positive effect of nutrient pulses under well watered conditions disappears under water stressed conditions. Our findings suggest that the variation in multiple resources may have complex feedback on exotic plant invasions and, therefore, it is critical to encompass multiple resources for the evaluation of fluctuating resource availability effects on exotic plant species. This will allow us to project the invasive trajectory of exotic plant species more accurately under future global change and human disturbance.
营养可利用性的波动通常促进外来植物的生长，被认为是驱动外来植物成功入侵的重要因素。虽然全球变化和人类干扰往往导致生态系统中多种资源发生改变，但是营养波动对外来植物的影响是否取决于其它资源可利用性的变化还知之甚少。本研究探究水分可利用性的变化如何调节营养脉冲对六种外来植物和六种本地植物生长的影响。实验设置正常浇水和水分胁迫两种处理。在每种水分处理下，以三种方式添加等量营养，包括持续供应、单个大脉冲和多个小脉冲。研究发现，在正常浇水的情况下，相对于营养持续供应，营养脉冲促进了外来植物的生长，而对本地植物没有显著影响。与之相反，在水分胁迫的情况下，水分的缺失抑制了所有外来植物和本地植物的生长。更重要的是，相对于营养持续供应，营养脉冲并没有促进植物的生长，这种现象在外来植物和本地植物均得到证实。研究结果表明营养波动对外来植物的影响在很大程度上取决于其它资源的变化。营养脉冲在水分充足的情况下促进外来植物的生长，而这种促进作用在水分胁迫的情况下完全消失。综上所述，本研究表明多种资源的变化可能对外来植物的入侵具有复杂的反馈作用。因此，同时考虑多种资源的变化，对评估资源可用性对外来植物入侵的影响至关重要。这将有助于更为准确的预测外来植物在未来全球变化和人类干扰下的入侵轨迹。.
Keywords: exotic plant; nutrient and water; plant invasion; resource availability; resource fluctuation; resource pulse.
© 2022 The Authors. Ecological Applications published by Wiley Periodicals LLC on behalf of The Ecological Society of America.