Wardle, Glenda M , Williams, Moira , Ironside, Joanne .
The invasive potential of Pinus radiata: seed production, dispersal and the role of fire.
Plant invasions are a major problem worldwide and yet we frequently miss the opportunity to investigate, and mitigate, the invasion process until it is too late. Here we outline a demographic approach to studying the incipient invasions of Pinus radiata from plantations into high diversity euacalypt woodlands in Australia. The extensive plantations of Pinus radiata provide a substantial source of seeds that disperse into native vegetation. The reproductive output of these self-sown pines was estimated to determine whether they are contributing to a second wave of invasion that may become self-sustaining after the plantation is harvested. Cone production, seed number and proportion of viable seeds per cone were quantified for two sites in the Blue Mountains west of Sydney, New South Wales. Reproductive trees varied considerably in cone production (1-400 cones), and cone number did not correlate to tree size. Tree ages were estimated using ring counts from increment cores to give the age-structure of the invading population. It appears that recruitment within 100m of the plantation has occurred consistently over a 55-year period, as there are individuals in each 5-year age class. However, recruitment may be more periodic at greater distances into the eucalypt woodland, a pattern consistent with the removal of seedlings by fire and additional pulses of seedlings after the first invading pines became reproductive. A survey of pine abundance in native eucalypt vegetation surrounding an experimental plantation revealed that the direction of spread was related to the prevailing wind. A recent fire killed smaller pine trees but led to the release of seeds from cones on larger trees that survived. The subsequent opening of remaining cones by black cockatoos, and favourable conditions for germination, led to a substantial pulse of seedling recruitment. Clearly managing fire has important implications for control of pine invasions
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1 - The University of Sydney, Institute of Wildlife Research and School of Biological Sciences, Heydon-Laurence Building, A08, The University of Sydney, Sydney, New South Wales, 2006, Australia
Presentation Type: Oral Paper
Location: Salon F - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 8:00 AM