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Project title

Impact of Invasive Plant Species on Biodiversity: the Significance of the Soil Seed Bank

Primary Funding Agency

Environmental Protection Agency

Co-Funding Organisation(s)

n/a

Lead Organisation

University College Dublin (UCD)

Lead Applicant

Bruce Osborne

Project Abstract

Despite increasing appreciation of the ecological and evolutionary importance of soil seed banks understanding of the impacts of invasive species on this dynamic component of plant communities has been neglected. In this study the effects of three major invaders Gunnera tinctoria Fallopia japonica and Heracleum mantegazzianum were investigated comparing invaded and uninvaded communities at different spatial scale: site plot (4 m2) and soil depth (0-5 5-10 10-15 cm). Samples were collected at two points in time in May and October. Invasion profoundly affected the structure of invaded seed bank communities. Gunnera tinctoria formed a large persistent seed bank (sensu Thompson et al. 1997) with an average value of 60428 i? 47131 (mean SD) seedlings m2. Heracleum mantegazzianum formed a large transient seed bank (9762 i? 390 seedlings m2) and was found exclusively in samples collected in October in the top soil layer. No seedlings of Fallopia spp. were recorded at the study sites. Diversity (measured by traditional diversity indices and taxonomic indices) at species genus and family level was significantly lower in invaded seed bank communities. The numerical abundance of grasses and forbs was significantly lower in invaded areas although the magnitude of the impact was species-specific and site-dependent. Dominance (measured by the Pielou and Simpson indices and dominance-diversity curves) was significantly higher in invaded communities and was independent of the reproductive strategy of the invaders. Species characterised by a persistent seed bank and/or by effective dispersal mechanisms were still found in the invaded seed bank. Conversely species forming only a transient seed bank virtually disappeared. Results showed that Fallopia japonica has a potential to alter seed bank communities within a short time scale (3-10 years) despite not forming a seed bank. Low seedling recruitment from the seed bank was also observed for Gunnera tinctoria at the study sites. This observation was supported by findings based on laboratory experiments which showed significant effects of light temperature seed age stratification and their interactions on seed germination for this species.

Grant Approved

�73,500.00

Research Hub

Natural Environment

Research Theme

Sectoral Impacts on Biodiversity

Start Date

01/12/2003

Initial Projected Completion Date

n/a