How forests carry out their own fire suppression management

How did forests ever cope before the era of government planned small scale bushfires? Forests had many brilliant systems in place that digested leaf litter, kept the understory damp and a layer of nutrient rich humus at ground level, all operating with clever symbiotic relationships between plants, animals and fungi.

Below is just a selection of extracts from research which shows how important these ground layer ecosystems are – and how vulnerable they are to planned government burns.

Blue Tongue lizards as fungi dispersers

‘…The authors of the paper given in the next reference button wrote…we observed a large adult Eastern Blue-tongued Lizard Tiliqua scincoides, move towards the base of a mature Coastal Rosemary shrub Westringia fruticosa and commence digging. We realised that the lizard was digging for fungi when it retrieved and quickly consumed a white, ball-shaped mass that had not been visible from the surface. At this point we disturbed the animal (which retreated a short distance) and recovered three more ball-shaped fungi which resembled the ‘eggs’ of immature stinkhorn or anemone fungi…One of these was offered to the lizard which immediately consumed it…and another was allowed to mature in our laboratory…

The fungus turned out to be Aseroe rubra. The authors summarized the reports of fungus consumption in two species of Egernia and six of Tiliqua. Taken together, these seven lizard species have been seen to eat a variety of fungi (mushrooms, boletes, truffles) but generally the fungi had not been identified even to genus. Earlier research had shown that some lizards had been shown to be capable of identifying plant food chemicals. The authors of the above-mentioned paper therefore suggested that lizards could be significant spore dispersers in areas where few mycophagous mammals…’

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Moths as leaf-litter converters

For CSIRO entomologist, Dr Marianne Horak, winning the prestigious John Obadiah Westwood Medal is the result of a lifetime studying Australia’s moths. Dr Horak is the only scientist in the country who is a lepidoptera (moths and butterflies) taxonomist. Her unique reference guide, “Olethreutine Moths of Australia”, describes 350 of Australia’s estimated 20,000 moths. Dr Horak explains in this podcast how the role of moths as biological controls for Australian horticulture is well known, but their value in preventing bushfires is not widely recognised.

Dr Marianne Horak: Yes, and especially in Australia there is an aspect which most Australians still don’t know, and is not known sufficiently; it’s that one large group of moths in Australia, 5000 species, their caterpillars largely feed on eucalypt and other myrtaceous leaf litter. They recycle the nutrients and they are very threatened by controlled burning in winter, which means the leaf litter builds up even quicker after that.

NC: So that could lead to more bushfires?

Dr H: Quite definitely. The controlled burning not only selects for tire resistant plants but by destroying those animals that break down the leaf litter, the leaf litter will build up more and quicker.

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Ted Edwards, and Entomologist, wrote similarly of the effect of fire on forest litter decomposing insects in the ACT National Parks Association Bulletin in 2009 in which he states;

‘…Control without fire

Biological agents are able to control litter without fire [italics added, Ed.] . There are numerous sites which may be cited, without fire for 50 years, which have no excessive litter build up. Unfortunately some studies of litter build up after fire have had no adequate controls where a genuinely unburnt treatment was part of the experiment. Most have had an “unburnt” treatment which has had less than a decade to recover and no cognizance was taken of the possible proximity of refugia. There have been no adequate studies on the effect of control burning on biodiversity. Such studies as have been done selected one or two groups to study and ignored the vast remainder of species affected. Often these groups were chosen inadvisedly: for example, ants were chosen because they were ubiquitous, common and comparatively easily identified. But ants are only one family, have a fairly standard biology, nest in protected places and are largely carnivorous or nectar feeders and can switch between numerous food sources. Biodiversity studies are notoriously difficult. As a retired Lepidoptera taxonomist (and there is only one full time working Lepidoptera taxonomist in Australia), I know that no even vaguely complete inventory of moths for any site has ever been attempted in Australia and Australia’s Oecophoridae moths are probably a major contributor to dry leaf litter breakdown. Attenborough says with some justification (Life in the Undergrowth) that if a virus wiped out all vertebrates the natural plant communities as we know them would hardly change but if the invertebrates were wiped out the world would change dramatically. Yet vertebrates are studied to exhaustion and invertebrates ignored…’

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From CSIRO Ecos Magazine 1999 and article by Anna van Dugteren and Robin Taylor;

The chronicles of a great recycler

ALMOST 50 years after unfolding the story of the bogong moth, Dr Ian Common has completed the final volume of what some might call his magnum opus: The Oecophorine Genera of Australia. The three-volume set of mono- graphs presents all that is known about the sub-family Oecophoridae or mallee moths, and is rapidly becoming known as the ‘bible’ on this extraordinary insect group. For Common, it represents a lifetime of discovery. There is the species he first caught as a child, the species he worked on while at university and then as a junior entomologist in Queensland, the species he trapped on Black Mountain behind CSIRO and around Canberra, and the many new species he captured on insect-collecting trips across Australia. More than 5000 species, or some 20% of the continent’s moth fauna, are mallee moths, making it by far the largest moth group in Australia. An estimated 3500 species are represented in the Australian National Insect Collection (ANIC), many of them undescribed. The whole of Europe, by comparison, has just over 100 species. Common believes the great diversity of Australia’s mallee moths is a product of their unique taste for myrtaceaus species, in particular the eucalypts.‘The evolution and speciation of the eucalypts after the Australian continent split from Gondwana opened a window of opportunity for the parallel evolution of mallee moths,’ he says. ‘Mature and dead eucalypt leaves are tough and leathery, have low nutritive value and are rich in phenolic compounds, including tannins, which makes them unpalatable to many organisms. Here was a developing food source that wasn’t seriously exploited by other insects.’ Through his research at CSIRO Entomology, Common discovered that mallee moths larvae could digest mature and dead eucalypt leaves. He and his colleague Dr Marianne Horak have since found that some mallee moths species even consume the faeces of animals that dine on eucalypt leaves, such as koalas and possums. The findings have helped to explain the amazing proliferation of mallee moths alongside eucalypts in many different habitats, from high-rainfall areas of northern Queensland to arid inland locations and temperate, sub-alpine and alpine environments. While the mallee moths depend on eucalypts, ecologists are now realising that eucalypts in turn depend on the moth to break down leaves and recycle nutrients back into Australia’s poor soils. But Common believes the moths’ crucial role in nutrient recycling is under threat from controlled burning practices which circumvent this natural breakdown by releasing nitrogen to the atmosphere. He points to the controlled burning of Jarrah forests of south-western Western Australia. ‘Way back in the early days of insect collecting, the Jarrah forests were rich in mallee moths,’ he says. ‘In more recent years when I have collected insects in these forests I have had an extremely small yield as the leaf litter and the mallee moths have been depleted.’

Mallee moths usually lay their eggs in narrow crevices or between living or dead leaves, often in large groups or masses. This helps to protect the eggs and larvae from temperature extremes and predators. Some species construct portable cases from leaf fragments, enabling them to move to the most favourable leaves for food.

Some species of mallee moths feed in the droppings of native animals such as koalas and possums which contain organic materials derived from eucalypt leaves. The caterpillars of most of these species complete their development in a single dung pellet in which they spin their cocoons, later emerging as adult moths. One of the koala scat feeding species was named in honour of Australia’s chief scientist, Dr John Stocker, as Telanepsia stockeri.

From
www.uoguelph.ca/~gbarron/MISC2003/feb03

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