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Invasive knotweed has greater nitrogen-use efficiency than native plants: evidence from a 15N pulse-chasing experiment


Habitats with fluctuating resource conditions pose specific challenges to plants, and they often favor a small subset of species that includes exotic invaders. These species must possess a superior ability to capitalize on resource pulses through faster resource uptake or greater resource-use efficiency. We addressed this question in an experiment with invasive knotweed, a noxious invader of temperate ecosystems that is known to benefit from nutrient fluctuations. We used stable isotopes to track the uptake and use efficiency of a nitrogen pulse in competition pairs between knotweed and five native competitors. We found that nitrogen pulses indeed promoted knotweed invasion and that this is explained by a superior efficiency in turning the taken-up extra nitrogen into biomass, rather than capturing an overproportional share of the nitrogen. Thus, temporary increases in nutrient availability might help knotweed to invade natural environments, such as river banks or nitrogen-polluted margins and wastelands, where nutrient fluctuations occur. Our experiment shows that resource-use efficiency can drive invasion under fluctuating resource conditions, and that stable isotopes help to understand these processes.

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We thank Nina Buchmann for advice and discussion on the experimental design, Yvonne Zürcher and Carole Adolf for assistance with measurements and processing the biomass samples, and the Botanical Garden in Bern for providing space for the experiment. We thank Casey terHorst and three anonymous reviewers for their helpful comments on previous versions of the manuscript. This work was supported by the Swiss National Science Foundation (SNF Project No. 122408 to OB) and the German Research Foundation (DFG Project PA 2608/2-1 to MP).

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OB and MP formulated the idea and conceived the experiment. MP, OB, AK, RW, and MF designed the experiment. MP and AK performed the experiment and RW performed the isotope analysis. MP analyzed the data. MP and OB wrote the manuscript; all other authors provided editorial advice.

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Correspondence to Madalin Parepa.

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The authors declare that they have no conflict of interest.

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This article does not contain any studies with human participants or animals performed by any of the authors.

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Communicated by Casey P. terHorst.

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Parepa, M., Kahmen, A., Werner, R.A. et al. Invasive knotweed has greater nitrogen-use efficiency than native plants: evidence from a 15N pulse-chasing experiment. Oecologia 191, 389–396 (2019).

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  • Biological invasions
  • Fluctuating resources
  • Interspecific competition
  • Invasiveness
  • Stable isotopes