Biology Reference
In-Depth Information
Island mountains
Granite outcrops are typically called inselbergs in reference to their island-like
appearance of rising abruptly from relatively flat landscapes.
3
Inselbergs can be
classified according to their general size and shape. For example, steep-sided and
dome-shaped formations are called bornhardts after a German geologist (Figure
5.3). Smaller inselbergs include formations such as castle koppies and nubbins
characterised by either block-shaped boulder stacks or conical rock piles. Granite
also forms scattered boulders called tors, ranging from loose clusters to entire
hillsides covered in low embedded rocks. Granite shields, called pavements,
protrude in flat landscapes, especially near Berrigan in southern New South
Wales (see Figure 5.3). These main types of rock outcrop are common on farms
and require management to maintain or enhance their habitat value for wildlife.
Ecological value of rocky outcrops
Flora
Rocky outcrops have a wide range of ecological values, many of which are not well
recognised. The range of environmental and climatic conditions on rocky outcrops
supports many different types of plants. In fact, studies in Western Australia have
shown that granite inselbergs are exceptionally important ecosystems which
support plants and vegetation communities found nowhere else in the world.
4
Granite outcrops on the South West Slopes of New South Wales support the only
known populations of Granite Bushpea, Quandong, Sandalwood, Rock Correa and
Woolly Ragwort in that region
5
(Figure 5.4).
Some of the species of flora that establish on the sun-exposed faces of rocky
outcrops are lichens and resurrection plants. Resurrection plants shrivel during
long periods without water but spring to life after rain, growing on sun-exposed
rock faces. Mosses and succulents are commonly found in large mats on the
sheltered parts of rocky outcrops. Plants such as these are collected by woodland
birds like the White-throated Treecreeper to use as nesting material. Because
steep-sided rocky outcrops are often inaccessible to livestock, they tend to support
many native plants that are rare or absent in the surrounding landscape.
Fauna
Many animals are specialised outcrop-dwellers: crevices, slabs and vertical rock
flakes provide habitat for species including the Snake-eyed Skink, Leaf-tailed
Gecko (Figure 5.5) and the Flat Rock Spider. These animals have flat bodies,
allowing them to shelter within narrow crevices. Deep cavities and rock shelves are
occupied by large skinks, goannas and pythons (see Box 5.3).
