The top of the McPherson Range is often draped in mist and cloud, and experiences an average annual rainfall of approximately two and a half metres. These cool wet mountain tops are covered in temperate rainforest that is dominated by the ancient Antarctic Beech (Northofagus moorei). Many gnarled individuals of this species are estimated to have stood amongst the mist mosses and filmy ferns for several thousand years. Numerous plant species are endemic to these cool forests.
Subtropical Rainforest
Down the plateau to the north, the uniformity of the beech forest is replaced in almost dramatic fashion by the luxuriance and floristic diversity of the subtropical rainforest. In contrast to the temperate rainforests, many trees here have large leaves and buttress roots, are enveloped in vines, and have large epiphytic ferns and orchids clinging to their branches. Red Cedar (Toona australis), Rosewood (Dysoxylum fraseranum), Crows Ash (Flindersia australis) and Booyongs (Argyrodendron spp.) abound. Strangler Figs (Ficus spp.), of which there are five local species, are a prolific food source for the fruit eating birds of the area.
As the south-easterly winds travel further down the slopes to the north, their moisture is lost and the drier elements of the rainforest dominate. These include the spectacular Hoop Pine (Araucaria cunninghamii) that tower over 20 metres above the other canopy trees.
Eucalypt Ecotone
Finally, the rainforest succumbs to the drier conditions and suddenly there is open eucalypt forest. The contrast is startling as these two plant communities, that are totally incompatible, engage in a territorial battle. Even the wildlife have adapted to either the enclosed or the open forest and seldom stray from one community to the other. The rainforest is a cool enclosed environment with many species of shallow rooted trees in several layers supporting epiphytes and vines and with ferns on the forest floor. Plants here have no resistance to fire, and because of the rapid breakdown of leaf litter, the lack of combustible materials ensures that fire seldom enters the enclosed forest.
By contrast, the eucalypt forest is an open, warm environment where the comparatively few species of trees have thick fire resistant bark. Combustible grasses grow on the forest floor. This forest has evolved to need regular fire if it is to resist the advance of the rainforest. The open forest species cannot germinate in the enclosed conditions of the rainforest, but the rainforest colonising species can germinate in the open forest, and will successfully annex the area if there are not major fires within a few years. In the absence of fire, the rainforests advance the ecotone at an average rate of 30 centimetres per year.
Biodiversity
A journey from the top of the McPherson range, down the northern slopes to the open forest country, will pass approximately 300 different species of trees, over 85 different species of vines, 90 fern species, and 90 orchid species as well as many species of mosses, lichens and fungi. Every kilometre down the slope sees compositional changes in the rainforest species with a complete change over of species from the top of the range to the edge of the rainforest. While the diversity of canopy tree species in the temperate and dry rainforests are relatively low, every hectare of subtropical rainforest will contain 100 different tree species.
Even in a well documented area like Lamington National Park, new plants are being found, classified and named. Such is the complexity of our rainforests. They present a continual challenge and source of interest to botanists, both professional and amateur, and to the many visitors that appreciate our outstanding forests.
