Geomorphology and climate
The Barrington Tops plateau is the southeastern extension of the New England Tableland, and separates the Manning and Hunter catchments. It reaches an altitude of 1586 metres and, except for an isolated peak near Ebor (Round Mountain, 1608 metres), is the highest area between the Southern Alps and New Guinea. Most of the southern and western margins are steep escarpments, with more gentle slopes occurring to the north.
 

The oldest rocks are Carboniferous sandstones, conglomerates, siltstones and mudstones. Granodiorite intruded in the middle Permian, and Tertiary basalts settled in valleys. Extensive weathering has since eroded the surrounding hills, with the granodiorite re-exposed in some areas and the basalt now remaining on the highest parts of the plateau. The climate ranges from temperate on the lower slopes to subalpine at highest altitudes. On the plateau, maximum temperatures in summer average 22-23 degrees, with mean winter minimum temperatures below freezing; a minimum of -17 degrees has been recorded at 1500 metres (Zoete, 2000). Although few rainfall measurements have been made up on the plateau, the mean annual rainfall is much higher towards the southeast - over 2000 mm - and declines to about 750 mm in northwestern parts (Dodson & Myers, 1986).

                                                                                                                                                             View from Thunderbolt's Lookout
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Vegetation
The range of elevations has resulted in an exceptional altitudinal series of vegetation communities. These include swamp, grassland, subalpine woodland, wet and dry sclerophyll forests, as well as dry, subtropical, warm temperate and cool temperate rainforests. The subalpine peat swamps are the largest outside the main southern alps. About 30 species of plants are considered rare or threatened; about 18 are possibly endemic to the plateau, including Tasmannia purpurascens (Purple Pepperbush) and nine new species of orchids (Heinrich & Dowling, 2000).
 

Many plants reach either the southern or northern limits of their distributions on the Barrington plateau. Species at their southern distributional limit include Sloanea woolsii (Yellow Carrabeen), Cryptocarya erythroxylon (Pigeonberry Ash), C. foveolata (Mountain Walnut), Orites excelsa (Prickly Ash), Lophostemon confertus (Brush Box), Acradenia euodiiformis (Northern Acradenia), and Nothofagus moorei (Antarctic Beech). Species at their northern distributional limit include Blechnum penna-maria (Alpine Water Fern) and Atherosperma moschatum (Southern Sassafras). The Southern Sassafras occurs as far south as southern Tasmania, but the NSW populations at Barrington and in the Blue Mountains are genetically and morphologically distinct from those in Victoria and Tasmania, and should perhaps be considered a separate subspecies (Shapcott, 1994).

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Nothofagus moorei
 

Nothofagus moorei (Antarctic Beech) is the dominant species of the cool temperate rainforest at Barrington, and is the focus of much of the experimental work in this research project. It is one of three species of Nothofagus occurring in Australia - the other two are N. cunninghamii, found in Victoria and Tasmania, and the deciduous N. gunnii, found only in Tasmania.  The genus is ancient and primitive, with a present-day distribution clearly indicating its Gondwanan ancestry - it is also found in New Zealand, New Guinea, New Caledonia and Chile, and has an extensive fossil record in Antarctica. The oldest evidence of Nothofagus is fossil pollen found in sediments as old as the Late Cretaceous (about 75-80 million years ago) (Hill, 1992). Fossilised leaves, both deciduous and evergreen, wood and, more rarely, reproductive structures such as woody cupules have been recovered from Tertiary deposits, most commonly in Australia and Antarctica.

    Nothfagus moorei  tree
 

Nothofagus moorei occurs from Barrington Tops to the Border Ranges-Lamington Plateau area on the Queensland/NSW border. It is one of the most geographically isolated species of the genus, separated by almost 1000 km from N. cunninghamii in Victoria, and by over 2000 km to the Nothofagus in New Guinea. It is found at altitudes between about 500 and 1550 metres and, while it appears to favour valley or south- and east-facing escarpment positions with ample moisture, deep soils and protection from hot dry winds and fire, it actually occurs in a variety of situations with different bedrock, soil type, altitudes and topographic positions.

                  Coppice growth                                                                                                                                                                Young tree

The species is evergreen, but loses about half of its canopy each autumn when these leaves turn a brilliant orange, to be replaced by new growth the following spring (Lowman, 1986). It flowers in spring and sheds seed in summer; however, this does not occur every year as N. moorei, like some other species of this genus (and many other genera), is a mast-seeder. Seedlings are observed mostly in high-light environments, such as roadside cuttings or occasionally at rainforest margins, but rarely within the rainforest, where regeneration is usually by coppicing.
                Summer foliage                                      Seed pods                                Seedlings                        Leaf bud                            Autumn foliage

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Vegetation at Barrington during the Quaternary
The Barrington plateau has been the subject of palynological studies that provide interpretations of past climate and regional vegetation changes back to 40,000 years BP (Dodson & Myers, 1986; Dodson et al., 1994; Sweller & Martin, 1997, 2001).
 

The area around Burraga Swamp (1000 metres) was then grassland with sparse Eucalyptus, becoming treeless for several thousand years (21,000-15,000 BP) during the last glacial maximum. Warmer and moister conditions in the early Holocene (after about 9,000 BP) facilitated an increase in Nothofagus and associated ferns, with the cool temperate rainforest reaching levels comparable with today by around 6,000 BP, and fluctuating slightly since with minor climate changes. It is unclear whether the present-day apparent migration of cool temperate rainforest to higher altitudes, also observed at other localities in northern NSW (Gilbert, 1959; Howard, 1981; Smith & Guyer, 1983; Read & Hill, 1985a,b), is a response to a slight warming in the last few centuries (Dodson, 1987) that is now accelerating, or whether the vegetation is still responding to the major climate changes following the last glacial maximum.

Return to top                                                                                                                         Burraga Swamp
 

References
Dodson, J.R. (1987) Mire development and environmental change, Barrington Tops, New South Wales, Australia. Quaternary Research 27, 73-81.

Dodson, J.R. & Myers, C.A. (1986) Vegetation and modern pollen rain from the Barrington Tops and Upper Hunter River regions of New South Wales. Australian Journal of Botany 34, 293-304.

Dodson, J.R., Roberts, F.K. & De Salis, T. (1994) Palaeoenvironments and human impact at Burraga Swamp in montane rainforest, Barrington Tops National Park, New South Wales, Australia.  Australian Geographer 25, 161-169.

Gilbert, J.M. (1959) Forest succession in the Florentine Valley, Tasmania. Papers and Proceedings of the Royal Society of Tasmania 93, 129-151.

Heinrich, A. & Dowling, W. (2000) Threats to the rare and threatened plant species of Barrington Tops. Proceedings of the Broom Management Conference, Australia, November 1998.

Hill, R.S. (1992) Nothofagus: evolution from a southern perspective. Trends in Ecology and Evolution 7(6), 190-194.

Howard, T.M. (1981) Southern closed-forests. pp. 102-120 In Australian Vegetation. Groves, R.H. (ed.) Cambridge: Cambridge University Press.

Lowman, M.D. (1986) Light interception and its relation to structural differences in three Australian rainforest canopies. australian Journal of Ecology 11, 163-170.

Read, J. & Hill, R.S. (1985a) Dynamics of Nothofagus-dominated rainforest on mainland Australia and lowland Tasmania. Vegetatio 63, 67-78.

Read, J. & Hill, R.S. (1985b) Photosynthetic responses to light of Australian and Chilean species of Nothofagus and their relevance to the rainforest dynamics. New Phytologist 101, 731-742.

Shapcott, A. (1994) Genetic and ecological variation in Atherosperma moschatum and the implications for conservation of its biodiversity. Australian Journal of Botany 42, 663-686.

Smith, J.M.B. & Guyer, I.J. (1983) Rain forest – eucalypt forest interactions and the relevance of the biological nomad concept.  Australian Journal of Ecology 8, 55-62.

Sweller, S. & Martin, H.A. (1997) History of the vegetation at Burraga Swamp, Barrington Tops National Park, Upper Hunter River region, New South Wales.  Proceedings of the Linnean Society of New South Wales 118, 23-50.

Sweller, S. & Martin, H.A. (2001) A 40,000 year vegetation history and climatic interpretations of Burraga Swamp, Barrington Tops, New South Wales. Quaternary International 83-85, 233-244.

Zoete, T. (2000) Vegetation survey of the Barrington Tops and Mount Royal National Parks for use in fire management. Cunninghamia 6, 511-578.

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