Acer negundo invasion along a successional gradient: early direct facilitation by native pioneers and late indirect facilitation by conspecifics

Authors

  • Patrick Saccone,

    1. Cemagref – Unité de Recherche Ecosystèmes Montagnards, 2, rue de la Papeterie, BP 76, F–38402 St-Martin-d’Heres Cedex, France
    2. Laboratoire d’Ecologie Alpine (LECA), UMR 5553 CNRS-Université Joseph Fourier, BP 53 X, F–38041Grenoble Cedex 9, France
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  • Jean-Philippe Pagès,

    1. Cemagref – Unité de Recherche Ecosystèmes Montagnards, 2, rue de la Papeterie, BP 76, F–38402 St-Martin-d’Heres Cedex, France
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  • Jacky Girel,

    1. Laboratoire d’Ecologie Alpine (LECA), UMR 5553 CNRS-Université Joseph Fourier, BP 53 X, F–38041Grenoble Cedex 9, France
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  • Jean-Jacques Brun,

    1. Cemagref – Unité de Recherche Ecosystèmes Montagnards, 2, rue de la Papeterie, BP 76, F–38402 St-Martin-d’Heres Cedex, France
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  • Richard Michalet

    1. Université Bordeaux 1, UMR INRA 1202 BIOGECO, Avenue des facultés, F–33405 Talence Cedex, France
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Author for correspondence
Richard Michalet
Tel: +33 5 40 00 88 95
Email: r.michalet@ecologie.u-bordeaux1.fr

Summary

  • Here, we analysed the role of direct and indirect plant interactions in the invasion process of Acer negundo along a natural successional gradient in the Middle Rhone floodplain (France). We addressed two questions: What are the responses of the invasive Acer seedlings to native communities’ effects along the successional gradient? What are the effects of the invasive Acer adult trees on the native communities?
  • In the three communities (Salix, Acer and Fraxinus stands) we transplanted juveniles of the invasive and juveniles of the natives within the forest and in experimental gaps, and with and without the herb layer. We also quantified changes in understory functional composition, light, nitrogen and moisture among treatments.
  • Acer seedlings were directly facilitated for survival in the Salix and Acer communities and indirectly facilitated for growth by adult Acer through the reduction of the abundance of highly competitive herbaceous competitors.
  • We conclude that direct facilitation by the tree canopy of the native pioneer Salix is very likely the main biotic process that induced colonization of the invasive Acer in the floodplain and that indirect facilitation by adult conspecifics contributed to population establishment.

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