Western Sydney woodland
Cumberland Plain Woodland is the original native vegetation community of much of Western Sydney. Cumberland Plain Woodland once covered an estimated area of about 125 000 hectares on the clay soils of western Sydney, extending north-west to Kurrajong and south-west to Picton. The area is drier than the coast, rainfall over this area ranges from 700 to 1000 mm per year, and experiences higher maximum and lower minimum temperatures. It occurs in the following local government areas of Auburn, Bankstown, Baulkham Hills, Blacktown, Camden, Campbelltown, Fairfield, Hawkesbury, Holroyd, Liverpool, Parramatta, Penrith and Wollondilly
Clearing for farming and urban development have reduced its original extent to small remnants, many of which are under threat. It is now listed as a Critically Endangered Ecological Community under the NSW Threatened Species Conservation Act and the Commonwealth Environmental Protection and Biodiversity Conservation Act.
Cumberland Plain Woodland is the original pre-european native vegetation community of the clay soils of Western Sydney. At the time of European settlement in the 1790s Cumberland Plain Woodland covered an estimated area of about 125 000 hectares on the clay soils derived from Wianamatta Shale of western Sydney, from Parramatta to Penrith and extending north-west to Kurrajong and south-west to Picton.
In Taken for granted: the bushland of Sydney and its suburbs, Benson and Howell (1990) provide a general introductory account to Cumberland Plain Woodland in the Sydney context. The following section is taken from the book:
West of Parramatta begins the gently undulating Cumberland Plain. It stretches south to Campbelltown and Camden, northwards to Richmond and Windsor, and west to the Nepean-Hawkesbury River. This is the driest part of Sydney; most of the plain receives less than 800 mm of rainfall per annum. Soils are deep clays developed from the shales of the Wianamatta Group, from the Bringelly Shale on the plain itself, and from the Ashfield Shale around the margins. Sandstone strata in the Bringelly Shale outcrop in cliffs on Razorback Range.
In April 1788, seeking better agricultural lands than those at Sydney Cove, Governor Phillip explored country to the west of Parramatta and typical of the Cumberland Plain landscape. He reported:
The country through which they travelled was singularly fine, level, or rising in small hills of a very pleasing and picturesque appearance. The soil excellent, except in a few small spots where it was stony. The trees growing at a distance of from 20 to 40 feet [6-12 m] from each other, and in general entirely free from brushwood, which was confined to the stony and barren spots.
An open, easily penetrable vegetation, free of shrubs, `brushwood', and presumably with an even grassy groundcover is the impression Phillip gives us of the original vegetation. The distances apart indicate there were about 70 to 200 trees per hectare. Tree densities in remnant stands today are generally much higher, but have a high proportion of younger trees as they are often regrowing after disturbance.
The `stony and barren spots' with `brushwood' are probably Hawkesbury Sandstone gullies where a more shrubby vegetation would be expected.
Thirty years later James Atkinson describes that 'one immense tract of forest land extends, with little interruption, from below Windsor, on the Hawkesbury, to Appin, a distance of 50 miles'. He had previously indicated that `forest means land more or less furnished with timber trees, and invariably covered with grass underneath, and destitute of underwood.'
Continuing his description of the Cumberland Plain, Atkinson writes: `The whole of this tract, and indeed all the forest in this county, was thick forest land, covered with very heavy timber, chiefly iron and stringy bark, box, blue and other gums, and mahogany'. He indicates that box and ironbark trees in particular abound in the forest lands.
Today the most common and widespread tree species of the Cumberland Plain are the Grey Box, Eucalyptus moluccana, and the Forest Red Gum, Eucalyptus tereticornis, and these predominated in the woodlands 200 years ago. The Grey Box tends to prefer rises, and the Forest Red Gum the lower hill slopes and depressions. On hilly country these may be accompanied by ironbarks, commonly Narrow-leaved Ironbark, Eucalyptus crebra, or perhaps Broad-leaved Ironbark, Eucalyptus fibrosa, though the latter often indicates the occurrence of Tertiary ironstone gravels and clays. Stringybark, Eucalyptus eugenioides, and Woollybutt, Eucalyptus longifolia, occur sporadically, though the main natural occurrence of Woollybutt is further east around Bankstown. Near creeks or on poorly-drained sites, Cabbage Gum, Eucalyptus amplifolia, Blue Box, Eucalyptus baueriana, Bosisto's Box, Eucalyptus bosistoana, and Broad-leaved Apple, Angophora subvelutina may be found. Such sites may also have groves of Swamp Oak, Casuarina glauca, or paperbark, Melaleuca decora.
The present understorey may be shrubby or grassy, depending on past disturbance or grazing treatments. The most common shrub species is Bursaria spinosa, which may be found in dense clumps or as scattered individuals. Less common shrubs are Dillwynia juniperina, Daviesia ulicifolia and Indigofera australis. Where the soils have been undisturbed, native perennial grasses still occur, particularly Themeda australis, Eragrostis leptostachya, Aristida vagans and Aristida ramosa, and the herbs Brunoniella australis, Lomandra filiformis, Dianella laevis and fern Cheilanthes sieberi. Where the soils have been ploughed or fertilised, exotic grasses such as Paspalum dilatatum predominate.
The relative abundance of shrubs and grasses at the time of settlement is now impossible to determine. The early writers describe a general lack of underwood, but with localised patches of shrubs. On visiting a farm at Liverpool in 1817, the botanist Allan Cunningham (not related to Peter Cunningham) wrote: `Like other farms in the neighbourhood it is overrun with the Bursaria spinosa now in fruit' Bursaria may have increased after settlement as a result of cultivating, changes in grazing, fire frequency, or a combination of these events.
Variations in floristic composition would have been caused by soil and drainage conditions. John Macarthur complained to Governor King that in 1805 land west of Liverpool was unsafe to feed sheep: `Almost the whole is of that wet kind which has been found so fatal to Sheep, or is covered with Scrubby brush Wood' . The `wet kind' of land, that probably caused sheep losses through liver fluke or footrot, would probably have been poorly drained land with stands of Casuarina glauca. `Scrubby brush wood' may refer to dense stands of Melaleuca decora. These are still common west of Liverpool. By comparison, woodlands around Camden were `chiefly of undulating, thinly-wooded hills covered with a sward of fine dry native pasture' and `dry, firm and ... in every respect so well adapted for a Sheep Pasture'.
Vegetation associated with the more rugged escarpments of Razorback Range and its spurs, particularly Donalds Range, often had a vine thicket understorey which in places approached dry rainforest. Remnants are found on outcrops of the sandstone strata of the Bringelly Shale, along gullies and cliff lines on sheltered north-east to south-east aspects. Small tree species with rainforest affinities found on Razorback include the well known Red Cedar, Toona australis, together with Notelaea longifolia, Guioa semiglauca, Claoxylon australe, Alectryon subcinereus, Rapanea variabilis and Myoporum montanum. Lianes and scramblers are plentiful, common species including Clematis glycinoides, Aphanopetalum resinosum, Cayratia clematidea and Stephania japonica. One vine, Cissus opaca, was not previously known to occur south of Port Stephens until collected on Razorback Range in 1968. There appears to have been a sparse understorey with banks of fern such as Pellaea falcata and Adiantum aethiopicum. Unfortunately this vegetation has been considerably altered by extensive removal of much of the tree canopy of Narrow-leaved Ironbark, Eucalyptus crebra, and Coastal Grey Box, Eucalyptus quadrangulata, and the invasion of the introduced African Olive, Olea europaea subspecies cuspidata, which forms a dense scrub preventing native shrub and herb regeneration.
Benson and Howell (2002) provide an assessment of historical literature and plant records for the species components and ecology of Cumberland Plain Woodland as described by early writers including Robert Brown, and how this compares with the composition and structure of remnants based on recent site monitoring at the Australian Botanic Garden at Campbelltown. View Benson and Howell (2002).
The most recent survey of western Sydney vegetation, that of Tozer (2003), has been based mainly on analysis of data from remnant sites and modelling based on soil and geological associations and ecological interpretations of current plant distributions. This work confirms earlier work (Benson & Howell 1990, Benson 1992) that included similar reliance on remnant vegetation, but interpreted this with more reference to historical evidence. View Tozer (2003).
Cumberland Plain woodland of western Sydney is part of a larger class of woodlands known as grassy woodlands because of the predominance of grasses and herbs in their understories. They occur on clay soils generally of moderate to high fertility. Related woodlands such as the Grassy White Box woodlands of the NSW Western Slopes, and grassy woodlands in the Hunter Valley may have many species and environmental features in common.
In contrast our nearby Sydney sandstone woodlands, found extensively in Royal, Ku-ring-gai and Blue Mountains National Parks are shrubby woodlands. These have a predominance of shrubby species and very few species in common with our Cumberland Plain woodland despite their proximity and similar rainfall. Shrubby woodlands are generally found on low nutrient infertile sandy soils (e.g. view Prober and Thiele 2004).
Cumberland Plain Woodland under threat
Cumberland Plain Woodland has been extensively impacted by two centuries of agriculture and urban development in western Sydney and is now confined to less than 10% of its original extent. Clearing for farms and housing has reduced its occurrence to small, often isolated and fragmented remnants, many of which are under threat.
Previously regarded by many as unsightly scrub, this bushland is now being recognised for what it is - a type of Woodland not found anywhere else in Australia, which is rare and threatened with extinction. It is now listed under the NSW Threatened Species Conservation Act (1995) (TSC Act) as a Critically Endangered Ecological Community, and the Federal government Environmental Protecton and Biodiversity Conservation Act (1999) as a Critically Endangered Ecological Community. Paricular woodland species also listed under the TSC Act are Pimelea spicata and Meridolum corneovirens which are listed as endangered species, and Marsdenia viridiflora which is listed as an Endangered Population.
The long-term management of remnants is of high priority. Conservation areas include Scheyville National Park and Mulgoa Nature Reserve. But smaller areas are also important links for wildlife movement between sites, and because some plant species have only survived in odd places such as a roadside site, old quarry etc and may now only occur in one or a few remnants, not necessarily in the conservation reserves.