Boorganna Nature Reserve is located on the south western edge of the Comboyne Plateau. It is approximately 6km west of Comboyne village, 35km southwest of Wauchope and 50 km north-west of Taree. The reserve is approximately 396 hectares and is a tiny, but significant, remnant of the extensive rainforest that once covered the plateau (NPWS 2004). Elevations in the reserve range between 360m and 732m above sea level. The landscape is dominated by steep slopes which form a gully into Mumford’s Creek.
The annual rainfall for the reserve is about 930mm (Bureau of Meteorology 2001). The predominant rainfall is in summer. To the west, a significant part of the plateau drains into Mumford’s Ck which then flows into the Ellenborough River about five km below Ellenborough Falls.
Geology and Soils
The Comboyne Plateau is Tertiary basalt topped residual. It was left behind following the excavation of the large valleys of the Hastings River to the north and the Manning River to the south. This basalt capping is part of the Comboyne Basalt flow, a Tertiary, 30 million year old flow. It is columnar jointed, mostly in small, less than 300mm columns giving rise to talus slopes and the potential for landslips. At Boorganna, Mumfords Ck cuts through the basalt cap exposing softer shales below. The underlying lithology is part of the Permian, 270 million year old, Manning Group. This group is composed of various sandstones, shales, conglomerates and mudstones, with some outcrops of serpentine (Department of Mineral Resources 1987). These can be seen in the creek bed downstream of Rawson Falls. A plunge pool has eroded a spectacular waterfall, the Rawson Falls, and the creek drops from 700m to 400m in less than 1km. From the Boorganna viewing platform over Rawson Falls, the geology can be seen in the cliff face, exemplifying erosion, plunge pools and columnar basalt flows.
The range of elevations and geology of the reserve provides a range of soil and habitat types from the wet sub-tropical rainforest through to wet and dry schlerophyll forests. The higher south-eastern section of the reserve has underlying Tertiary basalt rocks, with deep red fertile soils (krasnozoems) which support sub-tropical rainforest associations. Further down the slope, are underlying Permian sedimentary rocks enriched by shallower basalt soils, warm temperate rainforests occur in this area. Along the creek there are small alluvial arcs enriched by sediments from upstream. Associated with some of these, are some small pockets of sub-tropical rainforest. On the southern side of Mumford’s Creek are slopes of sedimentary rock with a drier northerly aspect that supports wet and dry schlerophyll forest.
Flora
The vegetation of the reserve is complex due to the range of soil types and the aspect. The reserve was surveyed by Alex Floyd, in 1976 and again in 2003. There are 13 significant plant species (NPWS 2004) and 36 fern species (Society for Growing Australian Plants 1991). According to Floyd (1976) there are 11 forest associations which can be grouped into six main forest types. The main forest types and main species in each are as follows:
Sub-tropical Rainforest: The major trees are rosewood (Dysoxylon fraserianum), black booyong (Heritiera actinolphylla), red carabeen (Geissios benthamiana), figs (Ficus sp) and stinging trees (Dendrocnide excelsa).
Warm temperate rainforest: The major trees are rosewood coachwood ( Ceratopelatum apelatum), sassafras (Cinnamomum oliveri) and the occasional brush box (Lophostemon confertus). Along Mumford’s Creek the dominant species is watergum (Tristaniopsis laurina).
Gully Rainforest: This appears in very narrow steep gullies, and is common in many coastal gullies in NSW. It is a mixture of the two preceding groups and is characterised by the association of bangalow palm (Archontophoenix cunninghamiana), whalebone fern (Strublus brunonianus), strawtree fern (Cyathea cooperi) and walking stick palm (Linospadix monostachya).
Dry Rainforest: This group occurs on northerly aspects and at the top of the Rawson Falls where the soil is shallow. The main species are grey myrtle (Backhousia myrtifolia) and shatterwood (Backhousia sciadophora).
Wet Schlerophyll Forest: This occurs on the moist sections south of Mumford’s Creek. It has blue gum ( Eucalyptus saligna), brush box, tallowwood (Eucalyptus microcorys) and New England Blackbutt (Eucalyptus campanulata).
Dry Schleropyll Forest: This forest of New England Blackbutt and black she-oak (Allocasuarina littoralis) occurs on the dry stony ridges and north facing slopes in the western section of the reserve.
Fauna
The reserve forms part of the Tapin Tops / Killabakh regional wildlife corridor (Scots 2003). A fauna survey undertaken by Tony Bischoff, in April 2003, recorded seven threatened species in the Draft Plan of Management (NPWS 2004). A total of 36 bird species including two vulnerable forest owls have been recorded in the reserve. Interestingly, several bird species uncommon to the region were recorded. This may be due to habitat modification in surrounding areas (Tony Bischoff personal observation).
References
1. Bischoff, T., (2003) Boorganna Nature Reserve, Fauna Survey, April 2003. Internal Report for NPWS, prepared by Tony Bischoff, Port Macquarie
2. Floyd, A. G., (1976) Boorganna Nature Reserve - Resource Inventory. Internal report to NSW National Parks and Wildlife Service
3. Gwalter, N. R., and Luckie, K. (2004) Boorganna Nature Reserve Draft Plan of Management. NSW National Parks and Wildlife Service
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Community Centre Resource Folder
In the Community Centre LIbrary there is a Boorganna Resource Folder for more detail on plants and animals of the Boorganna Nature Reserve.
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