Enhanced shoot investment makes invasive plants exhibit growth advantages in high nitrogen conditions

Abstract Resource amendments commonly promote plant invasions, raising concerns over the potential consequences of nitrogen (N) deposition; however, it is unclear whether invaders will benefit from N deposition more than natives. Growth is among the most fundamental inherent traits of plants and thus good invaders may have superior growth advantages in response to resource amendments. We compared the growth and allocation between invasive and native plants in different N regimes including controls (ambient N concentrations). We found that invasive plants always grew much larger than native plants in varying N conditions, regardless of growth- or phylogeny-based analyses, and that the former allocated more biomass to shoots than the latter. Although N addition enhanced the growth of invasive plants, this enhancement did not increase with increasing N addition. Across invasive and native species, changes in shoot biomass allocation were positively correlated with changes in whole-plant biomass; and the slope of this relationship was greater in invasive plants than native plants. These findings suggest that enhanced shoot investment makes invasive plants retain a growth advantage in high N conditions relative to natives, and also highlight that future N deposition may increase the risks of plant invasions.

摘要 资源输入通常会促进植物入侵，由此引发了人们对氮（N）沉降潜在生态后果的担忧，但目前尚不清楚入侵植物是否比本地植物更能从氮沉降中获益。生长是植物最基础的固有性状之一，因此相较于本地植物，优秀的入侵植物在应对资源输入时或许具备更优异的生长优势。本研究针对包括对照组（背景氮浓度水平）在内的不同氮素水平梯度，对比了入侵植物与本地植物的生长状况及生物量分配模式。研究结果显示，无论基于生长性状还是系统发育的分析框架，在各类氮素条件下，入侵植物的生物量均始终显著高于本地植物，且前者向地上部分配的生物量比例也高于后者。尽管氮素添加提升了入侵植物的生长速率，但这种提升效应并未随氮素添加量的增加而进一步增强。在所有入侵和本地物种中，地上生物量分配的变化与植株总生物量的变化呈显著正相关，且入侵植物的该相关关系斜率显著大于本地植物。上述研究结果表明，相较于本地植物，更高的地上部分投资使入侵植物在高氮环境中仍能保持生长优势，同时也预示着未来的氮沉降或将加剧植物入侵的风险。