Flora of the Stockton and Port Hunter sandy foreshores with comments on fifteen notable introduced species

摘要

Between 1993 and 2005 1 investigated the introduced plant species on the Newcastle foreshores at Stockton and Macquaries Pier (lat 32 degrees 56' S, long 151 degrees 47' E). At North Stockton in a rehabilitated area, cleared of *Chrysanthemoides monilifera subsp. rotundata, and planted with *Ammophila arenaria interspersed with native shrubs, mainly Acacia longifolia subsp. sophorae and Leptospermum laevigatum, is a rich flora of introduced species of which *Panicum racemosum and *Cyperus conglomeratits have gradually become dominant in the groundcover. Notwithstanding continuing maintenance, *Chrysanthemoides monilifera subsp. rotundata has re-established among the native shrubs, and together with Acacia longifolia subsp. sophorae, is important in sand stabilisation along the seaward edge of the dune terrace.The foredune of Little Park Beach, just inside the Northern Breakwater, is dominated by Spinifex sericeus and backed by Acacia longifolia subsp. sophorae-*Chrysanthemoides monilifera subsp. rotundata shrubbery. In places the shrubbery has given way to introduced species such as *Oenothera drummondii, *Tetragonia decumbens and especially *Heterotheca grandiflora.At Macquaries Pier *Chrysanthemoides monilifera subsp. rotundata forms an almost continuous fringe between the rocks that protect the pier against heavy southerlies. However, its presence on adjacent Nobbys Beach is localised and the general aspect of this beach is no different from any other along the coast as it is dominated by Spinifex sericeus.Many foreign plant species occur around the sandy foreshores at Port Hunter. Since the first coal exports in the 1850s the Newcastle wharves and ballast-ground at Stockton became points of entry for foreign species, either directly, or via stopovers at other Australian ports. Some of these, *Panicum racemosum, *Tetragonia decumbens, *Ursinia speciosa, *Hebenstretia dentata and until recently, *Heterotheca grandiflora, remained restricted to the Newcastle region, while others, e.g. *Chrysanthemum monilifera subsp. rotundata, *Hydrocotyle bonariensis, *Gladiolus gueinzii and *Oenothera drummondii, spread further afield, but only colonised their preferred coastal habitat. Many more species spread far and wide, their port of introduction no longer recognisable. Other species were introduced as garden plants, escaped and became naturalised. However, for most foreign, generally widespread, species their mode of entry can no longer be determined. 99 species were recorded in the six areas regularly visited, about 25% native to Australia, and 75% about evenly divided between species from Africa, Asia and Europe. More detailed information on 15 of the more notable introduced species is provided in an appendix.On the dune terrace vegetation of North Stockton, only about 20% of the 50 species are native to Australia, the only one of any prominence being Acacia longifolia subsp. sophorae. Nevertheless, on first impression this 'multinational' assemblage looks quite normal, and when one compares the ecological functioning of the 1930s vegetation with that of the present vegetation, it appears that, due to presence of more graminoids, and the fact that *Panicum racemosum produces a denser sward than Spinifex sericeus, the present vegetation is more effective in sand-catching and dune stabilisation than the vegetation in the 1930s would have been. However in view of the increasing influence of climate change, e.g. a rise in sea level and more extreme weather events, there is no indication that the present terrace, notwithstanding the increased density of the rhizomatous species and a sprawling shrubby vegetation along the crest, will endure such attacks any better than in the 1990s.