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Front. Plant Sci. | doi: 10.3389/fpls.2019.00337

Species-specific outcome in the competition for nitrogen between invasive and native tree seedlings

  • 1Department of Biology, University of Konstanz, Plant Interactions Ecophysiology Group, Germany
  • 2Institut für Biochemische Pflanzenpathologie, Helmholtz Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt GmbH, Germany

The outcome of competition for nitrogen (N) between native and invasive tree species is a major concern when considering increasing anthropogenic N deposition. Our study investigated whether three native (i.e. Fagus sylvatica, Quercus robur, and Pinus sylvestris) and two invasive woody species (i.e. Prunus serotina and Robinia pseudoacacia) showed different responses regarding morphological and physiological parameters (i.e. biomass and growth indices, inorganic vs. organic N acquisition strategies, and N allocation to N pools) depending on the identity of the competing species, and whether these responses were mediated by soil N availability. In a greenhouse experiment, tree seedlings were planted either single or in native-invasive competition at low and high soil N availability. We measured inorganic and organic N acquisition using 15N labeling, total biomass, growth indices, as well as total soluble amino acid-N and protein-N levels in the leaves and fine roots of the seedlings. Our results indicate that invasive species have a competitive advantage via high growth rates, whereas native species could avoid competition with invasives via their higher organic N acquisition suggesting a better access to organic soil N sources. Moreover, native species responded to competition with distinct species- and parameter-specific strategies that were partly mediated by soil N availability. Native tree seedlings in general showed a stronger response to invasive P. serotina than R. pseudoacacia, and their strategies to cope with competition reflect the different species’ life history strategies and physiological traits. Considering the responses of native and invasive species, our results suggest that specifically Q. robur seedlings have a competitive advantage over those of R. pseudoacacia but not P. serotina. Furthermore, native and invasive species show stronger responses to higher soil N availability under competition compared to when growing single. In conclusion, our study provides insights into the potential for niche differentiation between native and invasive species by using different N forms available in the soil, the combined effects of increased soil N availability and competition on tree seedling N nutrition, as well as the species-specific nature of competition between native and invasive tree seedlings which could be relevant for forest management strategies.

Keywords: Inorganic nitrogen, Nitrogen pools, Organic nitrogen, nitrogen uptake, plant competition, Woody invaders

Received: 20 Aug 2018; Accepted: 04 Mar 2019.

Edited by:

Boris Rewald, University of Natural Resources and Life Sciences Vienna, Austria

Reviewed by:

Brian D. Strahm, Virginia Tech, United States
Bruce A. Osborne, University College Dublin, Ireland  

Copyright: © 2019 Bueno, Pritsch and Simon. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Ms. Andrea Bueno, Plant Interactions Ecophysiology Group, Department of Biology, University of Konstanz, Konstanz, Baden-Württemberg, Germany, andrea.bueno@uni-konstanz.de