Rosebank Soils

Soils play an important role in the vegetation of the area, so a little time has been spent so as to gain a better understanding of soils around Rosebank.

Nightcap Range from Clunes
*move cursor over image to enlarge

The Nightcap Range

Rhyolite Cliff amphitheater at Minyon Falls

Rhyolite Cliff

Palm Valley - Booyong Forest

Palm Valley

Terania Basin Palm Forest

Bangalow Palms

The Rosebank foothills and the Nightcap Range lie on the southern rim of the caldera of the ancient Mount Warning shield volcano. The soils found here have eroded and formed predominantly from the Nimbin Rhyolites which are underlain with basalt layers produced from several different lava flows from Mt Warning. The Nimbin Rhyolites lava flows appeared through vents in the original basalt flows and can be found at their maximum thickness on the Nightcap Range eg at Peates Mountain where they are 1,600 feet thick. An excellent example of Rhyolites can be easily seen in the majestic cliffs of Minyon Falls.

The basalt and rhyolite lava flows have influenced the vegetation communities here. Warm temperate rainforest is found on red & brown Podzolic soils which have eroded from rhyolite lava flows. Many of these soils are crystal rich and found on the Nightcap Range & foothills.

Sub-tropical rainforest grows on the nutrient rich red soils eroded from basalt lava flows.

Rosebank Soils known as Krasnozems are the nutrient rich brown soils eroded from Andersite (basalt lava flows) which were once the soils of the Big Scrub sub tropical rainforests. The Krasnozems of Rosebank have suffered a high level of degradation since cultivation began and this is attributed to leaching of soils after clearing and the high usage rate of fertilisers. Drops of pH levels from 6.3 to 4 have been recorded over 4yrs under macadamia orchards especially where these had past land uses of bananas. Their original organic content under the old rainforests was 8–20% but this rapidly decreased to 7% after clearing and is now recorded as 3% in very exposed sites, as a result of a breakdown in the natural recycling system. Erosion and mass movement has now become a problem on steeper slopes.

Minyon Falls

Some of the crystals and rocks found around Rosebank include; Crystallised Quartz, Banded Obsidian and Chalcedonic Silica in the Upper Coopers Creek & Minyon area, Silicious Earth, Banded Rhyolite & Opals in the Whian Whian and Oplaised Wood around Rosebank.

The Nightcap Range

The Nightcap Range is known as a refuge for moist rainforest flora which once dominated the continent during Gondwanna times. The flora and fauna of the Range are known as a living evolutionary hotspot for biodiversity.

The Nightcap Range is protected in the National Parks and Wildlife Service (NPWS) Estate of the World Heritage listed Nightcap National Park & the Whian Whian State Conservation Area (SCA) and together they encompass approximately 10,500 hectares of the Nightcap Range. The Nightcap Range is dominated by several peaks and several waterfalls which drop off from both sides of the Range. The main peaks include; Mt Burrell (Blue Knob) 933m, Mt Neville 919m, Mt Nardi 812m, Mt Matherson 804m, Peates Mtn 604m. The main waterfalls include Minyon, Quandong & Protestor Falls.

The parks also support lowland species associated with the former Big Scrub and approximately 70% of the Nightcap NP is covered by varying types of rainforest. The remainder is mainly wet sclerophyll forest. Nearly 10% of the vascular native flora species known to occur in NSW occur here with 72 identified as threatened with extinction.

The Whian Whian SCA has similar natural heritage values to the World Heritage Gondwana Rainforest of Australia (formerly known as World Heritage Central Eastern Rainforest Reserves Australia) found in the adjoining Nightcap NP. The SCA supports a diversity of vegetation communities and species with ten broad ecosystem types and 520 plant species.

Combined, both parks have a remarkable representation of archaic (Gondwanic) rainforest species (flora and fauna) and ecosystem types and have a remarkable concentration of biodiversity in a relatively small area of forest.

The SCA also supports a diversity of 276 native animal species of which 36 species are listed as threatened species.

The Terania Basin is home to the largest and most extensive Bangalow Palm forest in NSW and along with its ancient 1000–1200 year old growth Brushbox Trees (Lophostemon confertus) it became the site of the well known Terania Blockade. You can read more about this blockade in the history section of this website.

Terania Cave

Rhyolite Cliffs

The rainfall of the Nightcap is the highest in NSW with greater than 2500mm per annum. Mean temps range from 19.1C–29.7C but in summer can reach the high 30s or more and humidity can be extreme. The sub tropical climate can produce destructive cyclonic storms in summer with heavy rainfall events and this has contributed to the diversity of flora found on the Range.

Nan & Hugh Nicholsons’ soft-cover series ‘Australian Rainforests Plants’ are brilliant for identifying flora species with exceptional photos. These are available from most bookshops.