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In Australia, the Proteaceae are a diverse group of plants. They inhabit a wide range of environments, many of which are low in plant resources. They support a wide range of animals and other organisms, and show distinctive patterns of distribution in relation to soils, climate and geological history. These patterns of distribution, relationships with nutrients and other resources, interactions with animals and other organisms and dynamics of populations in Proteaceae are addressed in this review, particularly for the Sydney region.
The Sydney region, with its wide range of environments, offers great opportunities for testing general questions in the ecology of the Proteaceae. For instance, its climate is not mediterranean, unlike the Cape region of South Africa, south-western and southern Australia, where much of the research on plants of Proteaceae growing in infertile habitats has been done.
The diversity and abundance of Proteaceae vary in the Sydney region inversely with fertility of habitats. In the region’s rainforest there are few Proteaceae and their populations are sparse, whereas in heaths in the region, Proteaceae are often diverse and may dominate the canopy. Research in the region has led to an understanding of their various responses to fire, dynamics of their populations in fire-prone landscapes, interactions with animals in pollination and dispersal, and of their breeding systems. This review examines results of this research and shows that ecological research has been uneven in Australian Proteaceae, with little work done on rainforest and alpine Proteaceae.
The review reveals an enormous range of interesting features of the Proteaceae of the Sydney region. It also identifies a large number of questions about ecological and evolutionary processes that are at the cutting edge of our current knowledge. The diversity of taxa of Proteaceae, the range of habitat, soil and climatic zones they occupy, the variety of life-histories (even among populations within species), fire responses, floral morphologies, pollinator types and breeding systems combine to make this family in the region a rich ‘test bed’ for many of these questions.
Natural vegetation of freely draining beach sand ridges in the valley of the Upper Myall River on the lower North Coast of NSW is sclerophyllous open forest or woodland. Based on previous experience on the nearby Eurunderee area, the vegetation on the sand ridges was classified into three types. These were mapped using aerial photographs and field observation. In transects, each 50 m long, the presence of species was scored in 10, 5 X 5 m quadrats. 48 such transects were used sampling all three types of vegetation on the sand ridges and also vegetation in periodically waterlogged sites adjacent to the ridges. Data from the transects, subjected to an ordination using principal components analysis, revealed clear separation between vegetation of the ridges and that of periodically waterlogged sites. In the ordination, vegetation of the ridges formed a continuum with the three types occupying characteristic parts of the continuum, reflecting their respective distributions on sands with different geomorphological histories. The most grassy, tallest forest, termed Dry Sclerophyll Forest (DSF) is on sands either recently disturbed or deposited (Holocene) or closely overlying other substrates. Banksia serrata occurs in DSF. The least grassy, most sclerophyllous, lowest forest or woodland, termed Dry Heath Forest (DHF), occurs on sands apparently little disturbed since they were laid down in the Pleistocene. Banksia aemula occurs in DHF. An intermediate forest, in which Banksia aemula and Banksia serrata occur together, Intermediate Dry Forest (IDF), is most widely found on the sand mass close to Bombah Broadwater. This sand is postulated to have been reworked during the last Glacial Period. In short, the vegetation of these sand ridges largely varies with time since they were laid down or last disturbed in a major way. Preliminary observations indicate the degree of podsolization of their soils is similarly related to this variation in time.