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Abstract
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Of all the major vegctational provinces in Victoria, the basaltic plains of the W. District are poorest in plant species. From the whole volcanic tract, stretching unbroken for 190 miles between Yan Yean on the extreme E. and Hotspur-Lyons district in the far SW., the total recorded number of higher indigenous plants is at present only 543 species; and it is most unlikely that any future investigations will alter this figure substantially. By comparison, the Brisbane Ra. (a small ‘island’ of sedimentary Palaeozoic rocks in the E. part of the basaltic area) has 420 species, while the Grampians sandstone (abutting to the NW.) has an exceedingly rich flora embracing 750 species of higher plants—almost one-third of the State’s indigenous vegetation.
It may be tempting to explain this poverty in terms of early and sustained pastoral activity. Certainly, the volcanic plains were the first pieces of land to be taken up by squatting families in the late 1830s and early 1840s, and their natural plant cover has been subjected to greater changes than anywhere else in the State. Through much of the basaltic region, native plants are now completely replaced by alien pasture grasses and clovers, crop plants, and a continuing influx of aggressive weeds; even to visualize the original ecological patterns has become difficult. Some basalt species are presumed already extinct, while about 100 others (or 18% of the whole) are now either very rare or localized—e.g. most of the 30 ferns and all but two or three of the 24 orchids. However, the various plant communities in equilibrium before white settlement are indicated by surviving remnants along roadsides and railway tracks, in paddocks too rocky to be cultivated, on a few permanent reservations of forest land, and in the shelter of gorges, cliff crevices or caves. It is apparent that the basalt plains, with associated lava or cinder cones, stony barriers, lakes and streams, never did carry the wealth of species so characteristic of adjoining forests on auriferous hills to the N. and of sandy hcathlands toward the coast.
The same lack of variety obtains also among lower cryptogams on basaltic land. E.g., a diligent survey of the moss flora has been rewarded by only about 85 species, compared with more than 120 species in the County of Normanby (at the W. boundary of the plains), and 140 in the County of Buln Buln which includes Wilson’s Promontory. Figures are not available for fungi or lichens, but casual inspection would strongly suggest a similar paucity. Only among the land and freshwater algae does diversity of kind seem to approach, or exceed, that in other vegetation provinces. |
