Saprobes are the group of fungi that act as decomposers, feeding on dead and decaying wood, leaves, litter, and other organic matter. To digest this they secrete enzymes that break it down. This releases and recycles vital nutrients for other organisms, and helps dispose of organic waste. Decomposers are essential for the survival of ecosystems.
Saprobes are the most common type of fungi. Many are too small to see with the naked eye. However, the saprobe group includes New Zealand’s best-known fungi with large fruiting structures (mushrooms), including most cultivated edible mushrooms.
Leaving a mark
Sapstain fungi produce a dark stain inside the wood they grow on, which reduces the commercial value of timber. But native wood that is stained blue-green by native cup fungi is valued for crafting into finely inlaid woodware.
Many saprobes produce stalked mushrooms that fruit on soil and wood. They include the introduced ink caps (e.g. Coprinus comatus) and field mushrooms (Agaricus campestris) on grass, and ‘big gyms’ (Gymnopilus junonius) on stumps and wood. In these species, the spores form on gills beneath an umbrella-shaped cap.
Polypore fungi produce spores from the inner surface of tiny tubes, under a structure that juts out like a shelf or bracket. Examples include large bracket fungi (Ganoderma species) and the annual rainbow bracket (Trametes versicolor).
The bright-orange pore fungus Favolaschia calocera is a mushroom, but with shallow pores on its underside. This introduced species was first reported in New Zealand in the late 1960s. It has weed status in many native forests, where it grows on a wide variety of wood.
Crusts, corals and cups
Other saprobic fungi develop spores on smooth outer surfaces (e.g. Aleurodiscus berggrenii, a crust fungus), on coral-shaped branches (e.g. Clavicorona pyxidata, a coral fungus) or within cup-shaped structures (e.g. Aleuria rhenana, a cup fungus). In most of these the spores are dispersed on the wind.
The stinkhorns, such as the red flower fungus Anthurus archeri, use insects to spread spores by attracting them to a sticky and stinking spore mass. They are common on wood chip mulch in gardens, and you are likely to smell their rotting-flesh odour before you see them.
Another commonly seen group of fungi are the sooty moulds, which form black carpets over the trunks and branches of beech trees. To get nutrients, sooty moulds break down sugars in honeydew excreted by scale insects that suck tree sap – the same honeydew taken by native birds and invasive wasps.
The bootlace mushroom
Harore, the native bootlace mushroom, was widely eaten by Māori. Its English name refers to the thick ribbons that weave along plant roots and through soil to find food. While it usually breaks down dead logs and roots, the mushroom can live as a parasite on crop plants such as kiwifruit and radiata pine. Freshly decayed wood taken over by this fungus may emit a weak light (known as bioluminescence).
Use by Māori
Māori traditionally used several saprobic fungi as food, including the toothed pekepekekiore (Hericium coralloides) and basket fungus or kōpurawhetū (Ileodictyon cibarium). Puffballs such as pukurau (Calvatia gigantea) were also used to staunch bleeding, and as anaesthetics. The wood ear or hakeka (Auricularia cornea) was both eaten and traded. In the late 19th and early 20th centuries huge quantities of this fungus were collected and dried by Māori, for export to China. This trade in ‘Taranaki wool’, as it was known, was managed by Chew Chong, who was recognised for his contributions to the dairy and fungus industries.