Photos: C & D Frith
Australia's Wet Tropics Rainforest Life
The Forest Floor:
- The forest floor is home to old fallen leaves and fruits, rotten branches, ancient or diseased trees, mosses, lichens, fungi and many animal species.
- Mosses of different greens cover the fallen tree trunks, which as they rot, also find bracket shaped fungal fruiting bodies growing on them. The fungi contain millions of microscopic single-celled reproductive spores, which are dispersed by wind, rain-splash, animals or by the fruiting body itself by exploding when mature.
- Fungi and bacteria are the catalysts of the decomposition process. They break up rotting vegetation into smaller pieces (detritus) and make food available for many creatures collectively known as detritivores.
- Living within leaf litter are the worms, springtails, amphipods, mites, millipedes and snails who graze upon small bits of detritus, which breaks it down further.
- Seeing leaf skeletons on the forest floor is an indication that the nutritious, once green parts of the leaf have been digested away by both fungi and small detritivores.
- To further speed up the breakdown process, rainforest cockroaches and beetles feed directly upon rotting wood.
- At the same time as receiving their own nourishment, the decomposers and detritivores release the important nutrients from the dead plant material through their own body waste and when they die, their own bodies. Tree roots can then recycle the nutrients as they absorb them from the soil for new plant growth.
- The plant roots generally grow on or just beneath the forest floor as this is where the nutrients are concentrated. Shallow roots are therefore more efficient than deep roots in rainforest environments. The systems extend out horizontally either from the trunk base or from buttresses at the base of the tree.
- Buttresses comprise woody flanged extensions that radiate outwards from the lower part of the tree base. They can reach enormous proportions around the base of a tree they may even be 10 m high. They help support a trees weight in the shallow soil by taking up strains and stresses.
- Continuing the food web, carnivorous invertebrates (eg scorpions, spiders and beetles) feed on tiny detritivores. In turn, these are then food for larger ground-dwelling carnivores such as frogs, skinks, birds and mammals. The larger. Warm-blooded animals provide food for blood-sucking leeches.
- Birds such as chowchillas, whipbirds, scrubwrens and fernwrens search for small invertebrates in the leaf litter during the day. At night, bandicoots nose their way through the litter and rotting logs looking for grubs, native rats search for fruits and small invertebrates, and rainforest dingoes stalk any suitable prey.
Additional Information: Courtesy of Damon Ramsey
The very bottom floor of the undisturbed rain forest is relatively open with little undergrowth such as grasses. Measurements in some rainforests have shown only 5% of the sunlight reaching the floor. Here, the leaves are often huge to catch what is left of the sunlight.
Where there are gaps in the canopy caused by disturbance, there is an explosion of tangled plants, such as Wait-a-while.
The structure and edge of the tropical rainforest can be appreciated with views from travelling on boats along rivers such as the upper Daintree, or Lake Barrine.
Script: Courtesy of Damon Ramsey BSc.(Zool) Biologist Guide