2) We assessed recovery of the native understorey plant community following removal of the non-native invasive Rhododendron ponticum L. from Scottish Atlantic oak woodland. We recorded understorey community composition in sites covering a gradient of increasing R. ponticum density, and across a separate series of sites covering a chronosequence of time since R. ponticum removal. We then compared both of these series to the target community found in uninvaded sites. We also analysed differences in soil chemistry between the sites to test for chemical legacy effects of invasion in the soil.
3) Native understorey cover declined as R. ponticum density increased, with bryophytes dropping to less than a third of the cover present in uninvaded sites and forbs and grasses being completely extirpated under dense stands.
4) Cleared sites showed no evidence of returning to the target community even after 30 years of recovery, and instead formed a bryophyte-dominated ‘novel
community’, containing few of the typical oak woodland vascular plants.
5) Contrary to expectation, soil pH, C:N ratio, and nutrient concentrations (N, P, K, Ca and Mg) were not affected by the invasion of R. ponticum, and chemical legacy effects in the soil were not responsible for the failure of the native community to revert to pre-invasion conditions. Instead, we hypothesise that the rapid formation of a bryophyte mat, coupled with the often-substantial distances to potential seed sources, hindered vascular plant recolonisation.
6) Synthesis and applications. Clear evidence of invasion history can be detected in the understorey plant community even decades after the successful removal of invasive R. ponticum. This finding demonstrates that native communities may be unable to recover effectively of their own accord following invasive species removal and will require further management interventions in order to achieve restoration goals.
Bibliographical noteThis research was funded by Scottish Natural Heritage, project reference 014299. We would additionally like to thank all the landowners who provided access to their land for this study.
- Atlantic oak woodland
- community ecology
- invasive species
- legacy effects
- Rhododendron ponticum
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Understorey plant community composition reflects invasion history decades after invasive Rhododendron has been removed
Maclean, J. E. (Contributor), Mitchell, R. J. (Contributor), Burslem, D. (Contributor), Genney, D. (Contributor), Hall, J. (Contributor), Pakeman, R. J. (Contributor) & Burslem, D. (Contributor), DRYAD, 1 Jan 2018
Data from: Understorey plant community composition reflects invasion history decades after invasive Rhododendron has been removed
MacLean, J. E. (Creator), Mitchell, R. J. (Creator), Burslem, D. (Creator), Genny, D. (Creator), Hall, J. (Creator) & Pakeman, R. (Creator), Dryad Digital Repository, 3 Jul 2018