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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. |
