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= Ecology of Tasmanian cool temperate rainforest macro-fungi =

Tasmanian cool temperate rainforests contain an incredible variety of macro fungi, many of which have not yet been formally described, and it is suspected many which are yet to be discovered. Fungi are heterotrophic, they are unable to fix carbon from the environment by themselves, but able to derive nutrition by decomposing wood debris and leaf litter from the forest floor. Many fungi have found specific roles within the forest ecosystem, as part of the breakdown process that recycles nutrients. This is especially true in climax rainforests which are not touched by fire events, and leaf litter and forest debris serve as a primary substrate.

Rainforest fungi have an incredible diversity, but can be described in broad terms as macro or micro fungi. Macro-fungi are the species with which we are most familiar as they represent the gilled mushrooms, tree brackets, or jellies, whereas the micro-fungi are usually present only at a microscopic level, but familiar to us as Penecillium sp. or Trichoderma sp. etc., better known as moulds. The micro-fungi represent the vast majority of fungi, but despite their ubiquitousness, they are an unseen part of the rainforest.

Many macro-fungi are saprophytes, they break down dead plant matter such as leaf litter and branches, but there are also many fungi which form symbiotic relationship with plants in order to benefit from additional nutrients. Some fungi are parasitic, and in some rare cases form relationships only with specific species as in the case of the 'Myrtle Orange' fungus Cyttaria and Nothofagus cunninghamii. The moist humid conditions found within tasmanias rainforests and mixed forests are perfect habitats for macro-fungi, with fungi being present most of the year in many forests in one form or another.

The ecology of cool temperate rainforests of Tasmania
Tasmanian rainforests are composed of four main types: callidendrous (tall trees with an open, park-like understorey); thamnic (shrubby understorey); implicate (short, tangled vegetation); and, montane (woodlands and forests at high altitude). It is hard to quantify how the different forests affect different species of fungi, but preliminary studies with the lichens and bryophytes indicate that obvious differences also occur among the three rainforest groups with respect to non-vascular flora.

Only a few studies have been done on fungi, but it is known that fungi are present in all rainforest types (including mixed forests), but given the requirements for moisture and humidity necessary for macro-fungi  the callidendrous, thamnic and mixed forests of mid to low altitudes would be more suitable environments. Tasmanias rainforests exhibit a close relationships with the Nothofagus forests of New Zealand and South America where relatives of the the ancient Gondwanan flora still flourish. Because of the floristic relationships observed in the higher plants we can also expect the fungal flora to be closely related to that of New Zealand and South America.

In Tasmania, rainforest occurs as extensive tracts which cover about 760,000 ha, or 10 percent of the State's land area. Tasmania’s cool temperate rainforests are quite different from the tropical and subtropical rainforests found at higher latitudes in Australia, as the diversity of higher plants is comparatively quite low. Tropical and subtropical rainforests have a high diversity of higher plants whereas the diversity in cool temperate rainforests are represented by the lower plants such as mosses and ferns, and also a high diversity of lichens and fungi.

Rainforests represent climax vegetation, forests which have reached a stable equilibrium, and undergo little disturbance when compared to wet or dry sclerophyll forest where some species require disturbance events, such as fire, for seed dispersal and/or germination. The composition of Tasmania's cool temperate rainforests follow environmental gradients such as soil and climate, the variety of plant species changing according to a combination of these two factors. While nutrients can be a limiting factor, rainfall is also  important. The minimum rainfall necessary for rainforest is c. 800 mm of annual rainfall, with a minimum monthly rainfall of c. 25 mm during January, February and March. Given minimum rainfall, rainforest is usually confined to river gullies and south-east facing slopes which are protected from wind and fires, and/or occur in pockets with supplemented groundwater or persistent mist, maintaining high humidity levels. If the annual rainfall is c., 1200 mm or more, rainforests occur over a wider range of soil and topography, and in regions of high rainfall, > 2000 mm annually, and where summer rainfall exceeds 50 mm per month, rainforest is not limited by soil, aspect or topography.

Tasmania's rainforests can be divided into two alliances ; the myrtle-beech alliance, or the pencil pine alliance. The myrtle-beech alliance forms the largest component of Tasmanian rainforest and occurs from sea level to an altitude of approximately 1000 m.  It can be further divided into  three sub-alliances, Callidendrous, Thamnic and Implictae. There is usually a continuum present in floristics and structure nevertheless each forest type are recognised readily in their typical forms. Mixed forest, comprised of an emergent layer of eucalypts over an under-story of rainforest species, is typically recognised as related to rainforest. Callidendrous forest are found mostly in the eastern half of the state, and in northwestern and central tasmania, whereas thamnic and implicate forests occur mostly in western and southwestern tasmania.

Callidendrous forests are represented typically by medium to tall forests and dominated by Nothofagus cunninghamii and/or Atherosperma moschatum. They are characteristic of fertile soils occurring over rocks such as basalt, dolerite, and more nutrient rich granites. Trees are well formed and widely spaced, and the understory is open, shady and park-like, providing a perfect habitat for macro-fungi. The density of ferns is high in Callidendrous forests with Dicksonia antarctica being very common. With increasing altitude the height of the forests decrease, with Nothofagus becoming multi stemmed with crooked leaning stems and a rich developemnt of epiphytic bryophytes and lichens.

Thamnic forests are characterised by well-formed trees of medium height and a distinct shrub layer. Two to five species may be present in the canopy of any one community, including combinations of Nothofagus cunninghamii, Atherosperma moschatum, Eucryphia lucida (Leatherwood), Phyllocladus aspleniifolius (Celery Top Pine), Athrotaxis selaginoides, and Lagarostrobos franklinii (Huon Pine). Implicate forest serve as the extreme to callidenrous forests in that they are found mostly on organic soils on mineral soils derived from nutrient poor rock-types such as quartzites and siliceous conglomerates or in poorly drained situations.

Fungal Diversity
Fungi are eukaryotic organisms that are dependent on living or dead organic matter for their nutrients. Fungi were the domain of botanists until genetic studies place the. They spread via elongated cells called hyphae. These hyphae can often be found at long strands commonly referred to as mycelium. using these mycelial thread the fungi are able to transport large amount of water and nutrients. The mycelium colonises a substrate by excreting enzymes which are used to break down substrates so the fungi can absorb nutrients. The mycelium is rarely seen but occasionally bundles of hyphae will form thick threads or cords called rhyzomorphs.

Rainforest fungi are at the most prolific during autumn and early winter after rain, dew, and drop in temperatures initiate the production of fruit-bodies. In the rainforest wet gullies and creek surrounds provide excellent moist environments for fungi to fruit on accumulated twig and leaf litter, small dead branches, rotting logs and animal dung. It is not unusual to find the underside small logs harbouring several species of fungi. Some species may occur in the same place year after year while others may appear once and reappear some years later.

The fungal diversity found in both wet sclerophyll and rainforest is quite rich but poorly understood. In a study done by Genevieve Gates, 495 species were found fruiting on soil, 330 were known to be ectomycorrhizal and 165 were considered decomposers. In addition, 146 species of macrofungi were associated with litter.

Not a great deal is known concerning endimism among rainforest fungi, but from the high degree of endemic vascular plant species of south east Australia and New Zealand, there is possibly a significant number of fungi endemic to the region, including Tasmania. Many species of fungi are restricted to the cool temperate rainforest habitat and one genus Cyttaria is regarded as being a Gondwanan relict co-evolving with Nothofagus.

Basidiomycetes
The majority of the macrofungi found within cool temperate rainorests are Basidiomycetes. They form large fruiting bodies which we recognise as mushrooms, boletes, puffballs, stinkhorns, jelly fungi, shelf fungi, bird's-nest fungi, etc. They produce their spores on microscopic club-shaped cells called Basidium. The spores are borne outside the cell on peg-like projections called Sterigmata at the top of the cell. Each basidium usually has four sterigmata but sometimes only two. The basidia are arranged on gills, inside pores or on the outer surface of the fruitbody, depending on the genus.

'''Table 1. Basidiomycetes found within Tasmanian cool temperate rainforests'''

Ascomycetes
Ascomycetes produce their spores inside microscopic, elongated sac-like cells called Asci. Each Ascus usually produces eight Ascoprores. When mature the ascus ruptures at the top and the spores are shot out into the air. The asci are usually formed on the fertile surface of the fruitbody, the Apothecium, but sometimes inside a small flask-shaped structure called a Perithecium. The Apothecium are cup shaped, and are the structure we know of as the cup fungi.

The most well known Ascomycetes are the Morchella species, known for their good eating, and often hard to find, they are more representative of mixed forest rather than rainforest. Other well known ascomycetes are the cup fungi that appear in a variety of sizes and colours and sometimes surrounded in light clouds of spores, or the Cyttaria sp. parasitic on Nothofagus.

'''Table 2. Ascomycetes found within Tasmanian cool temperate rainforests.'''

Myxomycetes
Commonly referred to as "slime moulds", they not formally considered a fungi, but included here becuase they are often reffered to as fungi and mentioned in many field guides. These organisms form colonies on a variety of substrates, and can look fungi-like in structure. They are considered to be in evolutionary terms very old, and very specialised, having departed sufficiently from the evolutionary path of fungi to constitute a subdivision of their own.

'''Table 3. Myxomycetes found within Tasmanian cool temperate rainforests'''

Ecological roles of fungi
Fungi are an important part of rainforest ecology, and fill many niches within these ecosystems. Two of the most fundamental roles are in assisting decay processes, with a a major role in the degradation of plant litter, but also by forming symbiotic relationships with plant species to provide nutrients in return for carbohydrates. In rainforests on nutrient poor soil the nutrient turnover is important for the health of the forest as a whole.

Fungi fill three broad roles, saprophytes, symbionts, or as parasites, but are not limited to one or the other. There are many saprophytes that also have the potential to become pathogens when growing on a living host, and cause heartrot within a tree.

Saprophyes
Saprophytic fungi live entirely on dead or decaying matter such as leaf litter and dead wood. Most macro-fungi are saprophytic, living on the dead remains of plant tissue. Their role in breaking down leaf and wood litter found on the forest floor is important as it enabling the recycling of nutrients, especially on nutrient poor soils. Some species specialise in leaf and twig decomposition, e.g. Marasmius and small Mycena species, whereas others tend to be found growing on larger branches and logs, e.g. larger Mycena species and polypores (bracket fungi).

As most fungi are both obligate aerobes and readily subject to water stress, normal decay processes are most rapid in moist, aerobic, mesothermic environments. In Tasmania, this is most easily seen in the wet mixed forests, where many species of Mycena and Marasmius invade fresh leaf litter. Other aspects of leaf litter degradation, decay of woody materials and recycling of nutrients by fungi remain largely uninvestigated, and the role of fungi in these processes is poorly understood. Some saprophytes are resposible for the different type of discolourations found on rotting logs, causing white, brown, or soft rots depending on the chemical substrate, these also being an issue in living hosts if the saprophyte turing pathogenic. Some saprophytes are specific to species, with Fomes hemitephrus having been identified as important in the decay of wood of Nothofagus cunninghamii.

Symbioses
Many rainforest fungi are mycrorrhizal, the most well known being amongst the Amanita sp. or Bolete sp., but there are others such as the Cortinarius sp. some of which appear to be specialist Nothofagus mycorrhizal species. Many of the macro-fungi seek nutrition through other means than feeding on debris and form a partnership with the higher plants. Their existence is one of mutual benefit whereby the fungi provide selected mineral elements, especially phosphate, for the plant, and the plant provides carbohydrates for the fungi. The great majority of vascular plants form a relationship with fungi, and it is widely regarded that it was this beneficial relationship that made them essential to the evolution of land plants. Fungi are unable to produce their own carbohydrates, but by supplying plants nutrients and water in return for sugars a beneficial symbiosis is formed. By means of these intimate associations with fine roots, mycorrhizal fungi enhance the growth of young trees and aid in the establishment of seedlings, by supplying water and inorganic substances from the soil in return for performed organic substances vital for their own survival.

Parasites
Most parasitic fungi obtain their nutrition from living tissue, but some parasitic fungi will live on dead matter after the death of the host, with the most well known of these being the bracket fungi, members of the basidiomycetes group of fungi. These are more often found on already dead and decaying tree stumps or logs, but they are known to cause defects in the heartwood of living trees, often gaining entry via crown and limb damage or trunk wounds. However, relatively few species of the higher fungi are pathogenic to the extent of causing disease and death within cool temperature rainforest trees. Species of Armillaria, a Basidiomycete, cause root rot and spread from tree to tree by means of root contact between neighbouring trees, and have been identified as a factor in eucalypt dieback.

Cyttaria is an obligate parasite restricted to Nothofagus, forming stem and twig galls on which it fruits with apparently no ill effects to the host. Today both Cyttaria and Nothofagus occur only in southern Pacific regions. In Tasmania and Victoria Cyttaria gunnii is restricted to Nothofagus cunninghamii on which it fruits in late spring and summer.

As an aside, it has been noted that some species of Cordyceps are parasitic on soil dwelling moth and beetle larvae. They gradually consume the entire body of the larvae until only the outer shell is filled with fungal tissue remains. At this stage the fungus grows up through the ground to produce a club-shaped fruiting body.

'''Table 4. Parasitic fungi within Tasmanian cool temperate rainforests'''

Introduced fungi
With the settlement of Tasmania by Europeans in the 1800's and the subsequent introduction of European animals and plants, many fungi have also been introduced. Many introduced fungi maintain their existing host relationships, in the case of Lactarius deliciosus and Suillus luteus, which are often found in radiata pine plantations, but some have managed to develop new symbiotic relationships as is the case with Amanita muscaria and Nothofagus gunnii, with records of A. muscaria becoming symbiotic with N. gunnii in both Victoria and Tasmania. A. Muscaria is a mycorrhizal species generally associated with pine, chestnut and birch, and is a common mushroom of radiata pine plantations throughout Australia. Chalciporus piperatus, a bolete, associated with coniferous and deciduous trees of the Northern Hemisphere has also been found growing with Nothofagus cunninghamii in east Tasmania.