Notes on the fungi of Thetford Forest

NOTES ON THE FUNGI OF THETFORD FOREST G. D. HEATHCOTE The following notes are based on a paper given in April 1991 at a symposium on Thetford Forest Park organised by the Forestry Commission in Cambridge. It was intended to give a naturalist's view of the fungi rather than that of a mycologist. For example, no attempt was made to discuss differences in the fungal flora with differences in pH, or compare the fungi of the region with those of any other. In fact very little serious scientific work appears to have been done there - perhaps because the area is sparsely populated without a resident mycologist.

Autumn 'fungus forays' organised by the SNS or other groups in the forest are usually very well attended, as are courses on the identification of fungi.

Although fungus field trips are very much a feature of the autumn some fungi can be found in all seasons. Flammulina velutipes, a yellow-ochre coloured toadstool with a brown velvety stem, can be found on rotten wood even in the middle of winter, and it is edible.

Most of the fungi of interest to the general public are relatively large and their fruiting bodies can be examined without the aid of a microscope, but some, such as the slime fungi (Myxomycetes) are small and insignificant but of great interest. Badhamia utricularis, for example, is far from eye-catching at the active amoeboid stage but may appear like a splash of paint on rotten wood and it suddenly changes into a mass of tiny sporangia. The slime fungi of Thetford Forest are poorly recorded although one third of the known species occur in Suffolk (Ellis & Ellis, 1988).

In contrast to the slime fungi, the Giant Polypore, Meripilus giganteus is often found growing at the base of deciduous trees and may have many fanshaped fruiting bodies each 50 cm or more across, growing from a common base. The Giant Puff-ball, Langermannia gigantea, may be 30 cm or more (sometimes much more) across, making a meal for a large family when fresh, and it is occasionally found in the more open parts of the forest.

Apart from species such as Fomes, Heterobasidion annosum, which are parasitic on timber trees and which are of great economic importance to the forester, the lignicolous species which attack dead wood are probably the most important in the ecology of the forest. The distinction between parasitic and saprophytic species is not always clear cut. Groups such as Polystictus, Polyporus, Fomes, Pholiota and Flammulina usually attack only the heartwood and it can be argued that they are not all true parasites. They tend to hollow out the centre of trees, weakening them structurally, so that they are likely to fall, killing the tree. They invade when the bark is damaged and the underlying tissues dry out. The high moisture content of the sap wood probably interferes with the respiration of fungal hyphae, preventing attack.

These fungi, together with bacteria, nematodes, collumbolids, woodlice, beetles and other 'mini-beasts' recycle the nutrients in dead stumps, fallen branches and leaves in the forest.

Many woodland fungi play what is probably a major but less obvious role in the ecology of the forest. They form mycorrhizas, a tree-fungus association

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which is not yet fully understood. Many species form mycorrhyzas, including Russulas, Boleti, Amandas, Lactarius and Hydnum species. Many are associated with particular tree species. For example, the Fly Agaric, Amanita muscaria, grows with birch, but the fungus can be found under pines, or even under oaks in Thetford Forest. Pinussylvestris is known to form mycorrhyzas with more than 30 species of fungi (Ramsbottom, 1953). When trees are infected with a fungus in this way they produce swollen, branched and yellow-brown roots. Externally there is a layer of closely-packed, interwoven hyphae, and no root hairs. The hyphae have no clamp connections, showing the fungi to be Basidiomyctes. Trees without mycorrhyzas may be stunted and nitrogen deficient. There is unboubtedly some degree of symbiosis, tree and fungus each contributing to the nutrition of the other. However, the Situation may have evolved from a balance between attack and defence against a parasite.

Although there must be some competition between fungal hyphae and the roots of healthy trees for food and space, fungi do not generally cover large areas of soil or form recognisable communities. Some fungi are intolerant of shade and will not grow under trees, e.g. the Parasol Mushroom, Lepiota procera, which commonly grows in the grass alongside tracks through the forest. It is one of the first fungi to appear in autumn and is welcome, being delicious. In general, cutting the grass verges favours fungi. Luxuriant grassland is relatively unfruitful for the larger fungi. The length of stem of these fungi is usually related to the height of the grass. The stem of L. procera can be up to about 30 cm., the length probably being controlled by the relative humidity of the habitat.

There may also be an association between forest fungi and insects. A wellknown example is between the fungus Ceratomella ulmi, the cause of Dutch Elm disease and the engraver beele, Scolytus scolytus, which carries the spores of the fungus from elm tree to elm tree in its fras. There are other interesting associations between beetles and fungi. David Nash provided the following examples. The very rare Endomychid beetle Lycoperdina succinata, is only found in Breckland where its larvae feed upon puffballs, as do those of the equally rare Caenocara subglobosa, which is only found in Norfolk and Suffolk. A very rare scarab beetle, Odontaeus armigera, feeds upon subterranean fungi and has been found in the Icklingham area. The forestry plantations are probably extending the ränge of some beetles associated with trees and fungi. The bracket fungus feeding Cis punctulatus has now been found at Hollesley Heath, although this tiny beetle was considered a northern species, as was Abdera triguttata, which feeds upon fungoidal wood, but a Single specimen of this beetle was found at Barton Mills in 1957.

The Stinkhorn fungus, Phallus impudicus, is very common in the forest. It produces a green-grey slime with a putrid smell which can be identified 50 m or more away. This slime contains the fungus spores which are carried away

by Carrion flies which were attracted by the smell. Hymentoptera may also be associated with woodland fungi. The Giant Wood-wasp, Uroceras (Sirex) gigas, carries Stereum gausapatum, which forms a pale, grey-fawn skin on conifers. The fungus mycelium grows ahead of the tunneling wasp larva,

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Suffolk Natural History, Vol. 29

breaking the wood down into suitable food for it. The fungus is also eaten by wasp larvae.

An extraordinary property of some woodland fungi may also be linked to insects. Some fungi can produce light in complete darkness. The oxidation of luciferin by luciferase produces a steady, faint, blue-green light, by the same process as used by glow-worms, Lampyris noctiluca. Heat is not given off by this reaction. It is possible that insects are attracted by the luminescence and spread the fungus spores. However, the well-known boot-lace like rhizomorphs of the Honey Fungus, Armillaria mellea, which give off light when damp, are hidden under the bark of infected trees and cannot be seen by Aying insects.

The forest fungi have other stränge properties, stränge shapes, and sometimes beautiful colours, making them of great interest to naturalists, but this link between man and fungi can hardly be considered an important part of the forest ecology. However, the use made by man and other animals of fungi as food must surely be considered. In general, the British do not eat wild fungi, although the ränge of cultivated species available in supermarkets is increasing rapidly. Many country people will not eat fungi found under trees. This fear is based on the habitat preference of the Deathcap, Amanita phalloides, which is responsible for the majority of deaths by fungal poisoning. I have been told that some Girl Guides camping at Santon Downham died after eating some in mistake for mushrooms. This may only be local folklaw but is widely accepted. In some years the Deathcap is very common in Thetford Forest; I have found it growing under a small clump of trees on the village green at Santon Downham, where the foresters' children can play.

One group of people make the most of the plentiful supply of edible fungi in the forest, which include Ceps, Boletus spp., the Shaggy Ink-cap, Coprinus comatus, Blewits, Lapista nuda, Wood Mushrooms, Agaricus silvestris and other related species, the Puff-balls and others previously mentioned. I refer to the Poles. Many Polish ex-servicemen settled in East Anglia after the war and worked in the forest. Their children are now adult, many speaking with an East-Anglian accent and speak no Polish, but they have inherited an interest in fungi as food. Unfortunately, one of the fungi most favoured as food on the Continent, the Chanterelle, Cantharellus cibarius, seems to be uncommon in Thetford Forest (unless I have looked for it in the wrong place) although the False Chanterelle, Hygrophoropsis aurantiaca, is particularly abundant.

Fungi form an important item of food for the wild animals of the forest, slugs and many insects, but it must be remembered that some that are poisonous to man can be eaten with impunity by some of these creatures.

Nibble marks do not make a toadstool safe to eat. The fungi are an exceptionally interesting group to study but must be treated with respect.

References Ellis, M. & Ellis, P. (1988). Fungi and slime moulds in Suffolk.

Naturalists' Society.

Trans. Suffolk Nat. Soc. 29 (1993)

The Suffolk

NOTES ON T H E FUNGI OF THETFORD FOREST

Ramsbottom, J. (1953). Mushrooms London.

and toadstools.

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Collins New Naturalist,

Dr G. D. Heathcote, 21 St. Mary's Square, Bury St. E d m u n d s , IP33 2AJ

Fingered Speedwell, Veronica triphyllos L. in Breckland v.c. 26.

I may have been hasty when I recorded: 'It is feared that V. triphyllos may be extinct on this field' (Trist, 1989). I referred to the Broom Road field which at the time was the only remaining site in the County. T h e plants still to be seen on T u d d e n h a m Gallops are f r o m a seedling put down for study and as a seed bank by the late Alex Watt in 1967.

David and Yvonne L e o n a r d , the rare plant surveyors for English Nature (in litt. 1991), reported to me that they had found five flowering plants of V. triphyllos within an area of Im 2 in an arable field corner on Caudle C o m m o n , Lakenheath. This was the f o r m e r site of V. triphyllos and this find had put it back on the Suffolk list.

T h e site is about 0.8 km south of the Broom Road field and east of Caudle Farm. I do not recall seeing this Veronica on Caudle C o m m o n since the late 1970s. In 1992, following three visits to the site, Yvonne Leonard found no V. triphyllos and the number of V. praecox plants was considerably less than the 1991 record. Whilst Marg Rutterford and I were recording V. triphyllos on the Broom Road field over the years 1974-1988 there were a number of occasions when both method of cultivation and changes of crops influenced the number of both V. triphyllos and V. praecox, which in some years was nil.

There is therefore hope that V. triphyllos will again occur. P. J. O . Trist.

Festuca

ovina

In 1984 two sets of plants of Festuca ovina from Landguard C o m m o n were sent to Dr. (now Professor) C. A. Stace at Leicester University for determination, and at that time he declined to name them (Trans. Suffolk Nat. Soc. 21, 49). Publication of New Flora ofthe British Isles (Stace, Cambridge University Press, 1991) has shown that these taxa were F. ovina ssp. ovina and F. ovina ssp. hirtula (Hackel ex Travis) M. Wilkinson. The discovery of F. ovina ssp. ophioliticola in 1988 (Trans. Suffolk Nat. Soc. 26, 72) establishes the existence of all three recognised British subspecies of F. ovina at Landguard.

Plants of Oenothera found beside View Point R o a d in 1992 proved to be O. fallax R e n n e r , providing one addition to the catalogue of species previously recorded. A . Copping.

Trans. Suffolk

Nat. Soc. 29 (1993)

Plate 8: S t i n k h o r n (Phallus impudicus), s h o w i n g drops o f f o e t i d slime o n the cap. (p. 59).