Introduction

This site is an introduction to the rainforests near Robertson in the Southern Highlands of New South Wales and an identification guide to the plants that grow in them.

Robertson is on the plateau west of the Illawarra escarpment and at the eastern edge of the Southern Highlands in the Wingecarribee Shire. With the highest point over 800 metres, winters are cool to cold, with occasional snowfalls and, at times, severe winds. Summers are mild. Because of the proximity to the coast, rainfall is high (average 1600mm per annum) diminishing with increased distance from the escarpment. Fogs are frequent. The characteristic red soil is derived from the volcanic rock, basalt, which covers the plateau near Robertson. Similar plateaux in New South Wales are Barrington Tops, Comboyne, Dorrigo and the Border Ranges.

The glossary explains some terms used, the more technical ones being avoided.

HISTORY

The rainforests near Robertson were once known as the Yarrawa Brush, estimated by Kevin Mills to have covered 2450 hectares. Because of their dense tangle of trees, shrubs and vines, these rainforests were avoided by settlers long after other parts of the Southern Highlands were cleared for grazing and agriculture. With the passing of the Robertson Land Act in 1861, many selectors began the difficult task of felling the rainforest. From early photographs and accounts of older residents, much had been removed or disturbed by the turn of the century for dairy farming and vegetable growing.

Some patches, however, remain in more or less original condition, especially on steep or stony sites unsuitable for farming, or where forest was deliberately conserved by landowners. The Nature Reserve within the village of Robertson is an example of such farsighted preservation; others being on private land. Elsewhere, there has been considerable regrowth, resulting in a highly picturesque landscape of verdant pastures and fields, interspersed with lush copses and larger forest remnants.

A fascinating account of the original vegetation and the early inhabitants was given by the botanist, William Woolls, after his visit in 1863. Interesting quotes include:

"The principal gum tree is of gigantic proportions, being more than 160 feet high and six or seven feet in diameter."

"Tree ferns abound."

"The settlers are surrounded by dense and beautiful woods."

"I cannot but express the pleasure I felt in visiting a wild and most romantic part of the colony where I had the opportunity of examining in the living state many plants quite new to me and noticing some of the results of free selection."

The earliest aerial photographs of the district available from the Department of Lands were taken in 1949. They show some forest remnants in more or less the same state as they are now. Others remnants have been destroyed or reduced in area. On the other hand, there are some places where the forest has advanced. It seems likely that those remnants that were there then and that still exist, are examples of the original rainforest. These are therefore of great scientific, scenic and cultural importance and should be preserved.

ECOLOGY

What is a rainforest ?

Rainforests are different from other Australian forests in that they have dense canopies of leaves which prevent most sunlight from reaching the ground. Sometimes, they are called closed forests in contrast with open forests of eucalypts and wattles. In places, tall eucalypts tower over the canopy where rainforest plants have colonized an open forest; in this district, Brown Barrel is such a eucalypt.

Why do rainforests grow at Robertson ?

Rainforests grow at Robertson because many ideal conditions exist in the area, including:

(1)

The soils are derived from volcanic rocks which contain more nutrients than the surrounding shales and sandstones.

(2)

The soils are structurally ideal for tree growth

(3)

The rainfall is higher and more reliable than in most other parts of New South Wales.

(4)

Fogs are frequent.

(5)

Bushfires rarely occur.

Are they similar to other rainforests ?

In New South Wales, there are different types of rainforest, each with distinctive trees and characteristics.

Most Robertson rainforests are warm-temperate types, grading to cool-temperate. Temperate rainforests have southern origins. Similar plants grow in Victoria, Tasmania, New Zealand, Lord Howe Island, and in the mountains of Queensland, New Caledonia, New Guinea and South America. Fossils of some of them are found in Antarctica.

In warmer places, subtropical rainforests grow. Many of the original coastal rainforests on the Illawarra were subtropical and remnants of this type can still be seen at Minnamurra.

A special type of subtropical rainforest called littoral rainforest grows close to the sea. It often has a low canopy because of salt and wind damage. An example occurs at Bass Point.

Closed forests and thickets of rainforest plants in areas of lower rainfall are called dry rainforest, examples of which can be seen on the Razorback Range near Picton and in the Shoalhaven Gorge.

What are the characteristics of our temperate rainforests ?

Cool-temperate rainforests have only one or two dominant trees. Pinkwood is the principal local example.

Warm-temperate rainforests have more species of trees in the canopy, the most common being Sassafras, Lillypilly, Coachwood and Blackwood. Other species are unevenly dispersed.

The canopy is of fairly even height, lower in rocky and windswept places. Another layer of smaller trees and shrubs is sometimes found below the canopy. Leaves are mostly simple, medium sized and toothed.

The trunks of trees, often covered with whitish lichens, do not have buttresses and are often single, but some older trees have coppiced, forming a ring of trunks around the original dead trunk. Such trees may be centuries old. Stumps sometimes coppice after felling.

Large woody vines are a distinctive feature at Robertson, but are not always seen in temperate rainforests. Ferns of several kinds grow in profusion on the forest floor, including three species of treeferns. Epiphytes, such as orchids, ferns, mosses and lichens, are common. Palms are rare. Strangler-figs, a feature of warmer forests, do not occur.

The existence of rainforests on northern and western facing slopes is remarkable, as this is unusual in southern New South Wales. Also notable, is the growth of rainforests dominated by Coachwood on basalt derived soils, an unknown condition in northern New South Wales.

Rainforests also grow on the lower grey shale soils near the overlying red basalt soils, because nutrients wash down to them.

The Treeferns have not been included in this site. The two common ones around Robertson are the Rough Treefern, Cyathea australis, and the Soft Treefern Dicksonia antarctica. The thin-trunked and very aptly named Prickly Treefern, Cyathea leichhardtiana, does occur in some places but is not at all common.

Where the size of a tree is referred to as small, medium or large, they are approximately the following height:

small: 4 to 10 metres
medium: 10 to 15 metres
large: taller than 15 metres


Thankyou for reading through the Introduction.