Data from: Responses of common and rare aliens and natives to nutrient availability and fluctuations

1. Global environmental change not only includes changes in mean environmental conditions but also in temporal environmental fluctuations. Because it is frequently suggested that common species, and particularly invasive alien species, are phenotypically highly plastic, they might benefit more from these fluctuations than rare native and rare alien species. Experimental tests, however, are still lacking. 2. Here, we tested whether alien plant species take more advantage of increases in resource levels and fluctuations therein than native species, and whether common species do so more than rare species. Therefore, we grew seven common alien, seven rare alien, nine common native and six rare native herbaceous plants, in one treatment with constantly low nutrient availability and five treatments with high nutrient availability that differed in temporal availability of nutrients (constant, increasing, decreasing, single large pulse, multiple smaller pulses). 3. We found that all species produced more biomass and longer roots, and had a lower root mass fraction under high nutrient conditions than under low nutrient conditions, irrespective of their origin and commonness. Among the high nutrient treatments, the temporal pattern of nutrient supply also influenced biomass production, root allocation and root thickness, but the magnitude and/or directions of these responses varied among the groups of species. Particularly, we found that alien plant species, irrespective of whether they are common or rare, produced more biomass, and had a higher root mass fraction when nutrients were supplied as a single pulse in the middle of the growth period instead of supplied at a constant rate, whereas the reverse was true for the native species. 4. Synthesis. Our study suggests that species origin does not drive differences in plant biomass production, root morphology and allocation in response to changes in mean environmental nutrient availability. However in our study, alien plant species, in contrast to native plant species, benefited from a large nutrient pulse. This suggests that increased fluctuations in nutrient availability might promote alien plant invasions.

1. 全球环境变化不仅涵盖环境平均条件的改变，还涉及环境时间波动的变化。既有研究普遍认为，常见物种尤其是外来入侵物种具有高度的表型可塑性（phenotypic plasticity），因此相较于本地稀有种与外来稀有种，它们或能从这类环境波动中获取更多收益，但相关实验验证仍较为匮乏。
2. 本研究旨在检验外来植物物种是否比本地物种更能利用资源水平及其波动的提升，且常见物种是否比稀有种更具这一优势。为此，我们栽培了7种常见外来种、7种外来稀有种、9种常见本地种以及6种本地稀有种草本植物，设置1种恒定低养分有效性处理，以及5种高养分有效性处理：这5种处理的养分供应时间模式存在差异，分别为恒定供应、递增供应、递减供应、单次大脉冲供应以及多次小脉冲供应。
3. 研究结果显示，无论物种起源与常见性如何，高养分条件下所有物种的生物量均更高、根系更长，且根质量分数低于低养分条件。在高养分处理组中，养分供应的时间模式同样会影响生物量生产、根系分配与根粗，但这类响应的幅度和/或方向在不同物种类群间存在差异。尤为值得注意的是，我们发现无论常见与否，外来植物物种在生长中期以单次脉冲方式供应养分，而非以恒定速率供应时，其生物量积累更多、根质量分数更高；而本地物种的响应结果则恰好相反。
4. 综合分析。本研究表明，物种起源并未导致植物在响应平均环境养分有效性变化时，在生物量生产、根系形态与分配方面产生差异。但在本研究中，与本地植物物种不同，外来植物物种可从大规模养分脉冲中获益。这一结果暗示，养分有效性的时间波动加剧或许会促进外来植物入侵。