Demographic mechanisms of disturbance and plant diversity promoting the establishment of invasive

Miia Jauni1 and Satu Ramula1,2,*   2017-07-04 23:26:10

1Department of Biology, Section of Ecology, University of Turku, 20014 Turku, Finland

2Aronia Coastal Zone Research Team, Åbo Akademi University and Novia University of Applied Sciences, Raseborgsvägen 9, 10600 Ekenäs, Finland

*Correspondence address. Department of Biology, Section of Ecology, University of Turku, 20014 Turku, Finland. Tel: +358 2 333 5717; Fax: +358 2 333 6598; E-mail: satu.ramula@utu.fi

Journal of Plant Ecology

VOLUME 10, NUMBER 3, PAGES 510–517

June 2017

doi: 10.1093/jpe/rtw049

Advance Access publication 18 May 2016

available online at academic.oup.com/jpe

Abstract

Aims

Community characteristics, such as disturbances and interspecific competition that affect the availability of microsites and resources, contribute to the success or failure of the establishment of exotic plant species. In particular, these two community characteristics may have adverse effects on plant emergence and survival, which are particularly important for population establishment and therefore it may be necessary to consider both these vital rates simultaneously when assessing demographic mechanisms. Here, we investigated the impacts of disturbance and interspecific competition on the establishment of a perennial invasive herb, Lupinus polyphyllus Lindl.

Methods

Over the course of 2  years, we conducted an experiment in 10 populations of this species in Finland in which we manipulated the levels of soil disturbance. We recorded community characteristics (i.e. the number of vascular plant species, vegetation height, and the proportions of bare ground, litter and moss), and observed the emergence and survival of L. polyphyllus individuals in study plots.

Important Findings

A mild disturbance (breaking the soil surface mechanically) slightly increased seedling emergence but did not affect plant survival. Instead, an intense disturbance (vegetation and litter removal) had no effect on seedling emergence, although it significantly increased the proportion of bare ground and, consequently, seedling survival. Survival was not affected by the height of the surrounding vegetation, but both seedling emergence and plant survival increased with an increasing number of plant species in the study plots. These findings demonstrate that single disturbance events may considerably promote the establishment of invasive herbs, although the overall effect and demographic mechanisms behind the increased establishment are likely to vary depending on disturbance type. Moreover, our results suggest that species diversity per se may not be a crucial mechanism for locally preventing the establishment of exotic plants.

Keywords: community invasibility, interspecific competition, invasive species, species richness, vital rates

Received: 9 November 2015, Revised: 25 April 2016, Accepted: 14 May 2016

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