Xu Xiao, Zhou Chenhao, He Qiang, Qiu Shiyun, Zhang Yan, Yang Ji, Li Bo, Nie Ming
Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, Institute of Biodiversity Science and Institute of Eco-Chongming, School of Life Sciences, Fudan University, Shanghai, China.
Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology and Centre for Invasion Biology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
Ecology. 2022 May;103(5):e3665. doi: 10.1002/ecy.3665. Epub 2022 Mar 14.
Eutrophication is believed to promote plant invasion, resulting in high growth performances of invasive plants and, therefore, the great potential for growth-induced intraspecific competition for light. Current hypotheses predict how eutrophication promotes plant invasion but fail to explain how great invasiveness is maintained under eutrophic conditions. In diverse native communities, co-occurring plants of varying sizes can avoid light competition by exploiting light complementarily; however, whether this mechanism applies to intraspecific competition in invasive plant populations remains unknown. Using a 2-year field nitrogen (N)-enrichment experiment on one of the global invasive plants, Spartina alterniflora, we found that the plasticity of light use reduced intraspecific competition and increased biomass production in S. alterniflora. This plasticity effect was enhanced when S. alterniflora had no nutrient limitations. In the N-enrichment treatments, the height difference among S. alterniflora ramets increased as light intensity decreased under the canopy. Compared with ambient N, under N enrichment, shorter individuals increased their light-use efficiency and specific leaf area in response to the reduced light intensity under the canopy. However, such ecophysiological plasticity was not found for taller individuals. Our findings revealed that the light-use plasticity of short individuals can be envisaged as a novel mechanism by which an invasive plant alleviates intraspecific competition and increases its invasiveness, challenging the prevailing perspective that the invasiveness of exotic plants is constrained by intraspecific competition.
富营养化被认为会促进植物入侵，导致入侵植物具有较高的生长性能，进而产生因生长引发的种内对光照的激烈竞争。目前的假说预测了富营养化如何促进植物入侵，但未能解释在富营养条件下如何维持强大的入侵性。在多样的本地群落中，不同大小的共生植物可以通过互补利用光照来避免光照竞争；然而，这种机制是否适用于入侵植物种群的种内竞争仍不清楚。通过对全球入侵植物之一互花米草进行为期两年的田间氮（N）富集实验，我们发现光利用可塑性降低了互花米草的种内竞争并增加了其生物量生产。当互花米草没有养分限制时，这种可塑性效应会增强。在氮富集处理中，随着树冠下光照强度的降低，互花米草分株之间的高度差异增大。与环境氮相比，在氮富集条件下，较矮的个体通过提高光利用效率和比叶面积来应对树冠下光照强度的降低。然而，较高的个体未发现这种生理生态可塑性。我们的研究结果表明，矮小个体的光利用可塑性可以被视为一种新机制，入侵植物通过这种机制减轻种内竞争并增加其入侵性，这对外来植物入侵性受种内竞争限制的主流观点提出了挑战。
