Seed ecology of the invasive woody plant African Olive (Olea europaea subsp. cuspidata): implications for management and restoration
Peter Cuneo A B C , Catherine A. Offord B and Michelle R. Leishman AA Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
B Botanic Gardens Trust, Sydney, Mount Annan Botanic Garden, Mount Annan, NSW 2567, Australia.
C Corresponding author. Email: peter.cuneo@rbgsyd.nsw.gov.au
Australian Journal of Botany 58(5) 342-348 https://doi.org/10.1071/BT10061
Submitted: 3 March 2010 Accepted: 27 May 2010 Published: 21 July 2010
Abstract
Knowledege of the seed ecology of invasive exotic species, including soil seedbank dynamics, is essential to understanding key factors in successful invasion and in identifying management opportunities. African Olive, Olea europaea L. subsp. cuspidata, is an exotic invasive woody plant in Hawaii, Norfolk Island and eastern Australia, and is now well established in the Cumberland Plain region of western Sydney, Australia. In the present study, the key aspects of the seed ecology of African Olive were determined for populations in western Sydney. Extracted seed germinated at a wide range of temperatures, consistent with tolerance of a wide range of climatic conditions. A seed-burial experiment indicated a slow decrease in viability down to 70.3% during the first year, followed by a rapid decline down to 14.7% in the second year. Probit analysis indicated that under field conditions, seed persistence in the soil was ~29 months (2.4 years). In situ germination was low (3.3%) and did not occur until the mechanical constriction of the endocarp was released through decomposition. The woody seed endocarp was found to be permeable to water, indicating that physical dormancy was not imposed by providing a barrier to water uptake. Within its invasive range, African Olive produces abundant seed. However, the rapid loss of viability of soil-stored seed results in a narrow window of opportunity for germination. The short persistence of seed in the soil may provide an opportunity for managers to achieve control of African Olive once mature plants are removed.
Acknowledgements
We thank Sue Lindsay of the Australian Museum for scanning electron microscope images, and Andrew Orme for photography of olive fruits. We also thank Amelia Martyn and Lotte von Richter of Mount Annan Botanic Garden for their thoughtful insights and discussion on the ecology of seeds. Carol and Jerry Baskin provided helpful discussions on seed dormancy within the Oleaceae. We acknowledge the comments and suggestions by two anonymous referees that have greatly improved the manuscript.
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