Nature’s Recyclers: from Dumbledore to Dung Roundheads
Christine Johnson gave a talk for Curracag on 13th December 2018 in the Dark Island hotel; it was organised by Martyn Jamieson.
Christine started with a diagram to show the importance of ‘Nature’s Recyclers’; in both terrestrial and marine environments there is a huge range of plants, from tiny plankton to huge, old trees. These take in from their surroundings water, air and various minerals, and through the power of sunlight digest them and form further plant material. Over time ephemeral parts of plants and eventually the whole plant will die, if it hasn’t been eaten: various animals from tiny larvae to elephants, consume different types of or parts of plants; then, in due course some of these ‘Primary Consumers’ are themselves eaten by carnivores – the ‘Secondary Consumers’, and they in their turn may be eaten by other carnivores: the ‘Tertiary Consumers’.
All these life forms consuming inevitably produce waste, and indeed in time die themselves, leading to masses of dead plant material, dung, droppings, faeces, and carcasses.
Where does it all go? Why are we not wading through a morass of waste products? – which, in a temperate woodland would amount to 5 tonnes of plant and animal material per hectare.
Although this is waste to the producers, it contains useful elements which can support a huge range of organisms: up to a thousand species per square metre, e.g. bacteria, fungi, and small invertebrates such as nematodes and larger worms, springtails and woodlice.
Christine then concentrated on the fungi, explaining that the part we see above ground is the fruiting body – which may drop spores [the ‘toadstool’ type], or catapult them over a distance [like puffballs]. The part in the growing medium – underground or embedded in leaf litter or wood – is a network of very thin tubes [hyphae] which collect and digest the material for growth; this network can extend over huge distances, in Siberia, for instance, over hundreds of square miles. Only fungi can digest cellulose. There are very small ones which grow on leaves and conifer needles; once they have started the process of breaking down leaf litter other large types move in, and may appear to be growing from the soil rather than reduced plant material. Fruiting bodies on the edges of some of these networks produce ‘fairy rings’. Some fungi grow on dead wood, the hyphae extending into the wood and softening it; when timber falls, other fungi may move in. Some opportunistic fungi will grow on processed timber such as pallets and chipboard.
Not all fungi are processing dead material; some cause problems in live plants, such as root rot in conifers; the oyster mushroom grows on standing trees and derives its nutrition from trapping and digesting nematodes.
While animal scavengers generally deal with the soft parts of other animals, fungi will grow on hard remains such as hair, feathers and bones, eventually digesting them.
Dung consists of partly digested plant material, mainly cellulose, and there are fungi that grow on dung and break it down. As these deposits are often scattered, to ensure that some spores may reach a hospitable site, they are scattered over the grazing area and ingested by the animals, then emerge already within a good growing medium. In the UK alone, there are about 400 species of fungi living on dung.
Christine’s talk was well illustrated with pictures of some of the amazing range of fungi, from large and robust ones to tiny delicate ones, some of them microscopic. It was a fascinating introduction to a small number of an extraordinary range of species and their very important function in the environment.