Decomposition of bracken litter

Botanical Journal of the Linnean Society, 73: 133-143. With 1 figure

July/September/October 1976

Decomposition of bracken litter

JULIET C. FRANKLAND, F.L.S.

Institute of Terrestrial Ecology, Grange-over-Sands, Cumbria

Investigations on the decomposition of bracken petioles, over a five-year period on six adjacent soil types, including moder-type humus, mull and peat, are reviewed. Changes in gross physical features, chemical composition, pH and dry weight are outlined. The succession of colonizing fungi is described and related to fungal activities.

Until the petioles were buried in the litter layer, decomposition occurred at different rates o n the various sites, the rate on moder > mull > peat, but the sequence of events was similar. Large proportions of readily leached components were removed in the first few months, but 9 5 % loss of dry matter was estimated to occur only after 11-23 years. The majority of fungi were species cosmopolitan on litter, the population becoming less specialized as decay advaliced. The succession resembled those on some other woody tissues, lignin and cellulose decomposers predominating before sugar fungi. From field observations and laboratory experiments, the Basidiomycete Mycena galopus (Pers. ex Fr.) Kummer appeared to be the most active of the fungal decomposers.

Some ecological and economic implications of the decomposition of bracken litter are briefly discussed, including its effect on soil type, and advantages of bracken compared with straw as bedding for farm animals.

CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . 1 3 3 Sites and methods . . . . . . . . . . . . . . . . . . . . 1 3 4 Stages in decomposition . . . . . . . . . . . . . . . . . . 1 3 4 The fungal flora . . . . . . . . . . . . . . . . . . . . . 1 3 6 Fungal action . . . . . . . . . . . . . . . . . . . . . 1 3 8 Rate of decomposition . . . . . . . . . . . . . . . . . . . 1 3 9 Some ecological and economic implications . . . . . . . . . . . . . 1 4 0 Acknowledgements . . . . . . . . . . . . . . . . . . . . 1 4 2 References . . . . . . . . . . . . . . . . . . . . . . 1 4 2 Appendix . . . . . . . . . . . . . . . . . . . . . . 1 4 3

INTRODUCTION

Gray & Biddlestone (1974), when estimating the annual production of organic waste in the United Kingdom, quoted a figure of 1,000,000 tonnes for fresh bracken, so the quantity of bracken litter removed by biological agents must be considerable.

I followed the decomposition of bracken petioles in Roudsea Wood National Nature Reserve (Grid ref. SD 330820) in the north-west of England over a period of five years (Frankland, 1966, 1969, 1974). The investigation was part of the former Nature Conservancy’s research programme on woodland ecosystems, in which the ultimate aim was to obtain a nutrient balance sheet

133 10

134 J . C. FRANKLAND

for various woodland sites in the Lake District. Bracken was studied because it was one of the dominant species of the ground flora. My aims were: t o identify the principal fungal decomposers, to determine the sequence and form of attack, to examine the effect of soil type, and, finally, to put a time scale on the process.

SITES AND METHODS

Full details of the sites and procedure used in this investigation are given in the previous publications. Roudsea Wood was particularly suitable for comparing the influence of certain site factors, because it has a range of adjacent soil types. Decomposition was compared on six of these: peat moss with open Callunetum; peaty alluvium with alder coppice; moder type humus, or mull-like mor, (a) with high oak wood and (b) with oak coppice; mull (a) with mature yew and (b) with hazel coppice. The soil pH ranged from 3.2-6.9 (0-50 mm). Bracken did not grow on the peat or mull sites, although it occurs on acid and calcareous soils. S. E. Allen & H. M. Grimshaw (pers. comm.) in a nutrient survey of bracken on 109 U.K. sites, where it was frequent or abundant, recorded a soil pH range of 3 .O-7.0 (0-1 50 mm).

The petioles were collected from a pure stand of bracken, on a shallow loam (pH 4.0) outside the Reserve, in November just before collapse of the fronds. After air-drying, weighing, removal of surface contaminants and labelling, 100 segments, 100 mm long and 5-9 mm diameter, were placed on each site, and samples taken on twelve occasions over five years. Changes in gross physical features, chemical composition, pH and dry weight were recorded. Three methods were used to investigate fungi which colonized the petioles: plating of washed particles of bracken (1 mm2 ) on nutrient agar; incubation of petioles in damp chambers, and examination of sectioned and stained material, Supporting evidence of the ability of individual species of fungi to decompose bracken was obtained by inoculating them on to bracken sterilized by gamma-radiation, and incubating under controlled conditions.

STAGES IN DECOMPOSITION

The chemical composition of the standing petioles when collected in November is shown in Table 1. They consisted largely of the complex components, cellulose and lignin. The high lignin and tannin and low nitrogen contents are characteristic of woody tissues. Even the green petioles in August contained only 0.3% nitrogen, whereas Allen & Grimshaw in their survey found that the pinnules with rachis (> 1 mm diameter) were much richer in nitrogen, containing 1.6-3.9% (O.D. wt) in July/August. The fronds were senescent when the petioles were cut and losses in chemical components had already occurred since August and before frond-fall (Table 2). The amount of lignin was not significantly different, but there was some change in the holocellulose content, while considerable proportions of sodium (50%), potassium (67%), phosphorus (77%) and soluble carbohydrates (88%) had been lost, either withdrawn t o the rhizomes or leached from the standing frond. Approximately 28% of the dry matter was lost between August and November; Swift (1971) found, that wood, similarly, usually loses one third to one half of its weight before i t falls.

DECOMPOSITION OF BRACKEN LITTER

Table 1. Chemical composition of standing senescent bracken petioles (November)

135

% O.D. wt mg/lOO g O.D. ~~

a-Cellulose 37.5 K 930 Lignin 28.0 Ca 170

Ash 3.5 Mg 40 Soluble carbohydrates 1.2 P 15 Tannin 0.9

Hemicelluloses (approx.) 26.0 Na 43

C N

48.10 0.24

The sequence of events in the litter layer was similar on the different sites. Lignin and cellulose decomposed slowly; 50% loss of holocellulose did not occur on any site until the third year and 50% loss of lignin was not recorded before the fourth year in the litter layer. The rate of cellulose and hemicellulose decomposition in litter has been shown to be inversely pro- portional to its lignin content, the highly resistant lignin probably acting as a barrier to micro-organisms (Satchell, 1974). Readily leached minerals, sodium and potassium, in particular, continued to be lost rapidly at the soil surface. This rapid release of minerals could be an important factor in the nutrient status of a site. Carlisle, Brown & White (1967) found that 31% of the potassium input to the ground flora of a Quercus woodland came from the litter and rainfall leachates of bracken. In contrast to sodium and potassium, calcium, phosphorus and nitrogen tended to accumulate in the petioles (Table 2). Increases were greater in woodland than on the open site, and may come from the tree canopy in precipitation and frass (Bocock, 1963; Carlisle et al., 1966). The C/N ratios were high in the fresh litter, and after five years were still more than 20, at which figure mineralization of nitrogen generally starts to

Table 2. Chemical composition of decomposing bracken petioles as percentage of components in green fronds (August) with

correction for dry weight loss

Standing senescent Dead litter' (Nov. of 1st year) (Sep. of 5th year)

Lignin Holocellulose Soluble carbohydrates

C N

Mg Ca Na K P

100 (approx.) >88

12

82 60

118 94 5 0 3 3 23

71 29

8

37 90

38 94

9 1

29

* Mean values for a mull, moder and peat site.

136 J. C. FRANKLAND

occur, rather than conversion to microbial protein (Table 3) . The pH value of the petioles increased from 5.2 rtl 0.04 when green to a mean for all sites of 6.1 rtl 0.14 after five years; the latter figure is close to the optimum for growth of many soil fungi.

The segments were still recognizable as bracken petioles after five years, but their appearance differed considerably on the various sites. On the moder sites, where decay had advanced furthest, the petioles were bleached and consisted of soft loose bundles of fibres and xylem vessels, entangled with soil debris and faecal pellets, buried beneath the turf in the F horizon t o a depth of 30 mm. At the other extreme, on the open peat site, the outer lignified cylinder was brittle, although still intact and lying on the surface, but much of the softer tissue inside had collapsed leaving longitudinal channels. These hollow petioles contained animals, such as mites and millipedes, foraging but not apparently tunnelling or eating the bracken, although Overgaard Nielsen found that Glomeris consumes the litter (Elton, 1966). The shelter may be particularly important in times of drought. Elton remarked on the richness of the fauna in bracken litter compared with nearby oak litter in the dry years of 1963-4.

Table 3 . C/N ratios of decomposing bracken petioles (after Frankland, 1974)

Number of Sites months in Original

the litter layer material Peat moss Coppice/mull Coppice/moder

0 >200 4 271 231 2 30

10 221 203 136 14 203 154 129 42 143 84 52 58 99 54 34

THE FUNGAL FLORA

Mycologists, anxious to find a biological control, have searched bracken for fungal parasites rather than saprophytes. The division between parasitism and saprophytism is not, however, a distinct one and in some cases it is debatable whether senility permits parasitism or parasitism initiates senility. The phylloplane flora of the green pinnae of bracken was examined recently by Godfrey (1974). He found a non-parasitic flora typical of angiosperm phylloplanes. In this investigation, approximately 3 90 species of fungi, including sterile forms, were recorded on senescent and dead petioles. Named species are listed in the Appendix. Most of them are well-known plant parasites and saprophytes, including Phycomycetes, Ascomycetes, Basidiomycetes and numerous members of the Fungi Imperfecti. Two of the latter were new British records, Cryptostictis hakeae Sutton and Endophragmia taxi M. B. Ellis. The first had just been described as a new species on the xerophytic Hakea in west Australia; the second, occurring under Taxus in Roudsea, had been recorded before only from Taxus in North America. These records no doubt reflect the distribution of mycologists rather than fungi. Only about 15% of the population occurred frequently and few fungi were specific to bracken. Several

DECOMPOSITION OF BRACKEN LITTER 137

Table 4. Succession of some common fungi on petioles of Pteridiurn aquilinum (data from Frankland, 1974)

LIVING- SENESCENT

1 2 3 4 5-6

pH 5.2 pH 6.1

C : N 200 C : N 3 0 Rapid loss of readily soluble minerals and carbohydrates

Loss of holo- Loss of lignin

<SO% matter

>20% original cellulose <SO% dry

remaining

Attack by weak Breakdown Breakdown Extensive fungal coloniza- Decline in fungal parasites. of phloem. of epidermis tion of xylem elements and fungal activity, Fungal lesions in Lignified cell fibres soil animals outer cortex; walls attacked dominant(?) phloem and non- by Basidio- lignified cortex mycetes penetrated by hyaline hyphae

PARASITES-PRIMARY- SECONDARY -+SOIL FUNGI AND SAPRO- SAPRO- PREDACIOUS SPP. PHYTES PHYTES

Rh opograph us pteridis Aureobasidium pullulans

Cladosporium herbarum Cylindrocarpon destructans > Epicoccurn nigrum

Basidiomycetes Trichoderma spp.

,

Pestalotiopsis neglecta , Chloridium spp.

4 (?) Lemalis sp. Volutella ciliata

Penicillium ~

SPP. Gliomastix ~

murorum Dactylella -----)

megalospora Phycomycetes

'sterile forms

species in genera such as Chloridium, Oidiodendron and Phialophora are also common on wood (Melin & Nannfeldt, 1934; Mangenot, 1952). More casual species were isolated from mull and alluvium than from the peat and moder sites, but, in general, the populations were remarkably similar. I t is therefore possible to describe a general pattern for the succession of common fungi (Table 4).

The succession consisted of overlapping waves of fungi and not of a series of distinct associations. This wave pattern is typical for herbaceous litter (Hudson,

138 J. C. FRANKLAND

1968). Weak parasites dominated first on bracken, followed by primary saprophytes, then secondary saprophytes and finally common soil fungi.

R hopographus and Aureobasidium formed lesions on the green standing petioles. These were mainly superficial and followed the long axis of the host cells, probably along lines of weakness. Even at this stage, some hyphae had penetrated as far as the inner parenchymatous cortex and phloem. A few fungi on standing fronds persisted in the litter layer for over a year, but after the first three months a different group of Fungi Imperfecti predominated. By the end of the first year, the phloem was no longer recognisable and Basidiomycetes, Mycena galopus (Pers. ex Fr.) Kummer in particular, were attacking the lignified cell walls. Basidiomycetes became dominant in the second year bleaching the litter and leaving ‘bore’ holes in the fibres (Frankland, 1966; photo 3) . These were followed by a further wave of Fungi Imperfecti in the third year, when the number of species reached a maximum and xylem vessels became crammed with hyphae (Frankland, 1966; photo 4). Springtails and mites by then were grazing the mycelium; nematodes were also conspicuous and debris was collecting inside the petioles. By the fourth year, the fungal invasion was declining and the population was more like that of the soil, but the nematode-trapper, Dactylella, became common. Finally Mucor and other Phycomycetes reached a climax in abundance, as total fungi decreased in numbers, until in some of the most rotten samples hyphae could not be found. The fate of the residue is unknown but animals and bacteria appeared to dominate over fungi. As Satchel1 (1974) has pointed out, there is an unfortunate separation of litter decomposition research from soil organic matter studies, although decomposition is a continuous process, and nutrient release can be as important to plant growth in the later stages of litter break-down as at the beginning.

Information on the fungus flora of other pteridophyte litters is too sparse for many comparisons to be made. Kamal & Singh (1970) examined decomposing leaf laminas of Adiantum, Cyclosorus (= Dryopteris), Dryopteris and Polypodium in the subtropics. Basidiomycetes and fungi typical of woody tissues were absent on these softer tissues, and Aspergilli, as usual, were more common on the subtropical litter than on the temperate.

FUNGAL ACTION

The fungal succession can be related to the changes which occurred in the litter, when the potentialities of the various species are considered. All but one (Acremonium pteridii W. Gams & Frankland) of eleven members of the succession grown on bracken caused a significant loss of dry weight (Table 5), and the succession represents a logical sequence of physiological potential on a substrate which is highly lignified and deficient in simple carbohydrates. The primary colonizers, e.g. Aureobasidium and Phoma, could decompose small quantities of lignin, cellulose or pectin, besides removing soluble carbohydrates. The secondary colonist, Mycena galopus, after a slow start, was the most active decomposer of Iignin and cellulose in culture, decomposing 25% lignin, 32% a-cellulose and 54% hemicellulose in a year, causing a typical white rot and ‘bore’ holes, as seen in the field. Other fungi accompanying M. galopus in the


succession, such as Pestalotiopsis and Chloridium, were also capable of attacking lignified cellulose. The final dominant, Mucor hiemalis, a well known sugar fungus, when grown on bracken removed only soluble carbohydrates. Its climax in the succession occurred when the initial sugar content was likely to be exhausted and when by-products of cellulose decomposition could be available. A significant increase of 14-21% (95% confidence) in the soluble carbohydrate content of bracken was in fact found when petioles were incubated for one year with M . galopus.

Table 5 . Percentage loss of dry matter from bracken petioles incubated with various species of fungi at

9.0°-15.5"C for six months

Mean values (n = 5)

95% confidence limits

Mycena galopus Gliomastix murorum v. felina ? Lemalis sp. Pestalotiopsis neglecta Aureobasidium pullulans Phoma SQ. Penicillium thomii Oidiodendron griseum Mucor hiemalis Chloridiurn sp. Control without inoculum

16.1 10.3 8.8 7.8 7.1 5.6 5.1 4.4 4.1 3.6 0.3

2.7 2.4 1.8 0.6 0.8 0.6 0.7 0.8 1.4 0.4 0.8

RATE OF DECOMPOSITION

Decomposition was a very slow process on all sites. In Fig. 1. the weights of dry matter remaining on a peat, mull and moder site are compared over a seven-year period. Estimated values for the seventh year were obtained from similar samples exposed for eight years by J. S. Waid & M. J . Woodman (unpubl. data). Significant differences between sites were recorded at most samplings. In the fourth year, for instance, 64.3-74.9% (95% confidence) remained on peat, 41.4-61.4% on mull and 23.0-41.0% on moder. From these data, 0. W. Heal (pers. comm.) calculated the instantaneous fractional rate of loss ( k ) constant in time, where W is the weight of material remaining at different sampling times, t is time in years, and

(Jenny, Gessel t3 Bingham, 1949; Olson, 1963; Heal, 1972). From this it was estimated that, on these sites, the time for 95% loss to occur ( 3 k ) was 11-23 years. These are probably minimum values, for it was assumed that weight loss follows an exponential form; but in long-term experiments more organic matter is found to accumulate than is predicted (Satchell, 1974). Decomposition is likely to be even more prolonged when the fronds are delayed in reaching the ground; this often occurs when fronds collapse on to one another. In

140 J . C. FRANKLAND

comparison, Quercus leaves decompose on the same sites in about two years (Bocock & Gilbert, 1957), whereas it has been estimated that 95% loss of CaZZuna vulgaris (L.) Hull stems, on blanket bog at 549 m, occurs in 57 years (Jones & Gore, in press).

The different rates of decomposition on the six Roudsea sites appeared to be related to the speed at which the petioles were incorporated into the litter layer, rather than to the organisms of the various humus types. After three years in the field, loss of weight was greatest in the moder and deep mull sites, where close ground vegetation or deep litter would provide more moisture and additional nitrogen, than in the sparse cover of the shallow mull or peat moss, where drying-out of the petioles occurred regularly. Percentage loss of dry matter from petioles incubated with soil inocula from the different sites did not differ significantly. There are reports of much speedier decomposition of bracken in other localities, which may be related to continuity of moist conditions (A. S . Wati, pers comm.).

I 1

t 50

40

I

T

1959 I960 1961 1962 I963 t964 1965

Figure 1 . Percentage of the initial amount of dry matter remaining in samples of decomposing Pteridium petioles on a peat moss (s), coppice/mull (A) and coppice/modcr (0 ) site. Mean values with 95% confidence limits. (From Frankland, 1974).

Nitrogen is probably one of the most important overall factors limiting decomposition of these petioles. After addition of 0.5% nitrogen in the form of calcium nitrate, loss of dry weight from petioles incubated with Trichoderma viride Pers. ex Fr. was doubled (95% confidence). Heal (1971) examined, by multiple regression, the loss of dry weight of 17 plant species, including these bracken data. The multiple regression equation was derived from data on nitrogen, soil pH and mean annual temperatures. Provisional results indicate that nitrogen content is responsible for over 40% of the variability in dry weight loss.

SOME ECOLOGICAL AND ECONOMIC IMPLICATIONS

In conclusion, it can be said that the decomposition of these bracken petioles is typical of terrestrial litter, in that the greater proportion of primary


production passes through decomposers and not herbivores. The fungal decomposers are mostly cosmopolitan litter types, the population becoming less specialized as decay progresses. This pattern is usual for green plants, and, as Elton (1966) observed, is repeated by the fauna of bracken. Initially, chemical and physical properties of the plant limit the organisms which can survive on it, but, as they are altered, the communities of the ground litter zones have more in common with one another. In detail, the succession of fungi on bracken is distinct from that described for other plants, but it has characteristics of both woody and non-woody substrates. The succession on pine-wood stumps (Meredith, 1960), in which lignin-decomposers precede most sugar fungi, is similar. Many variations on the same theme are likely to occur on other sites. In particular, the species occupying the basidiomycete niche appears to vary with locality, and it would be interesting to know to what extent this is so, and the controlling factors. The slow decomposition can be a major influence in altering an ecosystem, since it results in an accumulation of litter, the amount, as shown, depending on the site. A raw peaty humus develops from this accumulation, so that mineral soils tend to become organic.

Some ecological and potentially economic merits of bracken depend on properties of the litter rather than the living plant. The slowly decomposing beds of fronds give protection t o animals in drought: and frost. I t shelters both micro-fauna and macro-fauna, such as bank voles (Elton, 1966). Other plants, however, may be smothered and regeneration of trees inhibited (Tansley, 1949). The economic use of bracken litter is probably confined t o the open areas of hill farms.

In hill areas, where few cereals are grown, bracken is still harvested as bedding for animal stock. Wider use of this crop may be necessary in the United Kingdom, if the current reduction in fertilizer subsidies and rise in straw prices continue. On Westmorland grassland farms, where straw is purchased from eastern counties, the price of wheat and barley bedding straw has increased by over 60% since 1973 t o about El5 per ton, approximately 0.75 tons being required per calf in 12 months. Apart from the comfort of the stock, the main purpose of bedding is to absorb soluble and volatile compounds of nitrogen and potassium from the urine and dung. This traditional manure, unlike slurry, is usually free of animal disease and provides important ground shelter from frost. Bracken litter for farm use is usually harvested in autumn, as the fronds are turning brown, so that palatability and dangers of toxicity are absent. Serious fungal pathogens appear to be absent at this stage; a new species of Pithomyces was isolated in this investigation, but there is no evidence that it causes facial eczema of sheep, attributed t o the related P. chartarum (Berk. & Curt.) M. B. Ellis.

Bracken litter has some important advantages over straw. Its large surface area, with divided lamina and hollow petioles, provides particularly warm bedding with high absorbency (Russell, 1908), and its brittle petioles do not form extensive mats, so that it is easier to handle with a fork. I t also has a higher nitrogen content than wheat or barley straw (Russell, 1908; R. M. Boothroyd, pers. comm.). As discussed, nitrogen is a limiting factor in the decomposition of bracken, but farm practice has shown that, if the nitrogen content of bedding litter is increased to 1.8-2.0% by addition of urine or dung,

142 J. C. FRANKLAND

available nitrogen is not removed from the soil, and decomposition occurs rapidly (Shaw, 1961).

ACKNOWLEDGEMENTS

I am grateful to Mr S . Seal of the Ministry of Agriculture, Fisheries and Food and to staff of the Cumbria College of Agriculture and Forestry for information on bracken litter. I also thank Mr A. D. Bailey and Miss P. L. Costeloe for their assistance in the preparation of this paper.

REFERENCES

BOCOCK, K. L., 1963. Changes in the amount of nitrogen in decomposing leaf litter of sessile oak (Quercus petraea). J. Ecol., 51: 555-66.

BOCOCK, K. L. & GILBERT, 0. J. W., 1957. The disappearance of leaf litter under different woodland conditions. PI. Soil, 9: 179-85.

CARLISLE, A., BROWN, A. H. F. & WHITE, E. J., 1966. The organic matter and nutrient elements in the precipitation beneath a sessile oak (Quercus petraea) canopy. J. Ecol., 54: 87-98.

CARLISLE, A., BROWN, A. H. F. & WHITE, E. J., 1967. The nutrient content of tree stem flow and ground flora litter and leachates in a sessile oak (Quercus petraea) woodland. J. Ecol., 55: 61 5-27.

ELTON, C. S., 1966. The pattern of animal communities. London: Methuen. FRANKLAND, JULIET C., 1966. Succession of fungi on decaying petioles of Pteridium aquilinum. J .

FRANKLAND, JULIET C., 1969. Fungal decomposition of bracken petioles. J. Ecol., 57: 25-36. FRANKLAND, JULIET C., 1974. Decomposition of lower plants. In C. H. Dickinson & G. J. F. Pugh

GODFREY, B. E. S., 1974. Phylloplane rnycoflora of bracken, Pteridium aquilinum. Trans. Br. mycol.

GRAY, K. R. & BIDDLESTONE, A. J., 1974. Decomposition of urban waste. In C. H. Dickinson & G. J.

HEAL, 0. W., 1971. In Tundra Biome. 0. W. Heal (Ed), Working meeting on analysis of ecosystems,

HEAL, 0. W., 1972. In Tundra Biome. 4th International meeting on the biological productivity of

HUDSON, H. J., 1968. The ecology of fungi on plant remains above the soil. New Phytol., 67: 837-74. JENNY, H., GESSEL, S. P. & BINGHAM, F. T., 1949. Comparative study of decomposition rates of

orzanic matter in temperate and tropical regions. Soil Sci., 68: 419-32. JONES, H. E. & GORE, A. J. P. (in press). A simulation of production and decay in blanket bog. In 0. W.

Heal & D. F. Perkins (Eds), The ecology of some British moors and montane grasslands. Berlin: Springer-Verlag.

KAMAL & SINGH, C. S., 1970. Succession of fungi on decaying leaves of some pteridophytes. Annls Inst. Pasteur, Pans, I 19: 468-82.

MANGENOT, F., 1952. Recherches mkthodiques sur Ies champignons de certains bois en dicomposition. Revuegbn. Bot., 59: 381-99, 437-71,477-519, 544-55.

MELIN, E. & NANNFELDT, J . A., 1934. Researches into the blueing of ground wood-pulp. Svenska SkogsvFor. Tidskr., 32: 397-616.

MEREDITH, D. S., 1960. Further observations on fungi inhabiting pine stumps. Ann. Bot. (N.S.), 24: 63-78.

OLSON, J. S., 1963. Energy storage and the balance of producers and decomposers in ecological systems.

RUSSELL, E. J., 1908. On the use of bracken as litter. J. Bd. Agnc. Fish., 15: 481-7. SATCHELL, J. E., 1974. Introduction. Litter-interface of animatehanimate matter. In C. H. Dickinson

& G. J. F. Pugh (Eds), Biology of plant litter decomposition, 1: xiii-xliv. London: Academic Press. SHAW, K., 1961. Value of different litters as bedding materials. Technical News Letter, NL/160/1/61.

National Agricultural Advisory Service. SWIFT, M. J., 1971. Proc. iv Colloq. Pedobiol., Dijon, 1970: 430. TANSLEY, A. G., 1949. The British Islands and their vegetation. Cambridge: Cambridge University Press.

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(Eds), Biology of plant litter decomposition, 1:3-36. London: Academic Press.

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DECOMPOSITION OF BRACKEN LITTER

APPENDIX

Species of fungi recorded on decomposing petioles of bracken

143

PHYCOMYCETES Mucorales

Absidia coerulea Bain. A. corymbifera (Cohn) Sacc. & Trott A. cylindrospora Hagem Mortierella sp. (M. elongata group) M. isabellina Oud. M. jenkinii (Smith) Naumov M. marburgensis Linnem. M. minutissima van Tieghem M. parvispora Linnem. M. ramanniana (Moller) Linnern. M. spinosa Linnem. Mucor fragilis Bain. M. genevensis Lendner (?) M. hiemalis Wehm. M. racemosus Fresen. M. silvaticus Hagem M. subtilissirnus Oud.

ASCOMYCETES Eurotiales

Hemisphaeriales

Hypocreales

Sphaeriales

Pseudoeuro tium sp.

Echidnodes sp-

conidial Nectria inventa Pethybr.

Chaetomium erechlm Skolko & Groves Gelasinospora adjuncta Bain. Perisporium vulgare Corda Sordaria fimicola (Rob.) Ces. & De Not. Xylaria sp.

conidial Hyaloscypha dematiicola (Berk. &

conidial (?) Lemalis sp. Microscypha grisella (Rehrn) Sydow Mollisia sp.

Helohales

Br.) Nannf.

BASIDIOMYCETES

Marasmius sp. Mycena galopus (Pers. ex Fr.) Kummer Typhula quisquiliaris (Fr.) Corner

Agaricales

FUNGI IMPERFECT1 Sphaeropsidales

Ceuthospora spp. Coniothyrium fuckelii Sacc. Cytospora spp. Phaeocytostroma sp. (close to P. ambigua

Phoma spp. Phomopsis sp. Pleurophomopsis sp. ?Stagonospora sp.

(Mont.) Petrak)

Melanconiales Cryptostictis hakeae Sutton Pestalotiopsis neglecta (Thiim) Stey.

Acremonium pteridii W. Gams & Frankland Moniliales

Alternaria sp. Aspergillus fumigatus Fres. Aspergillus spp. Aureobasidium pullulans (de Bary) Am. Botrytis cinerea Pers. ex Fr. Cephalosporium spp. Chloridium spp. Cladosporium herbarum Link ex Fr. Cladosporium spp. Cylindrocarpon destructans (Zins) Schultze Cylindrocarpon sp. (C. ditissima group) Dactylella rnegalospora Drechs. Dictyosporium tomloides (Corda) GuCg. Endophragmia taxi M. B. Ellis Epicoccum nigrum Link ex Fr. Fusarium avenaceum (Fr.) Sacc. Gliocladium roseum Bain Gliornastix cerealis (Karst.) Dickinson G. murorum var. felina (Marchal) Hughes (?) Isaria sp. (?) Nodulisporium sp. Oedocephalum sp. Oidiodendron griseum Robak 0. tenuissimum (Peck) Hughes Paecilomyces farinosus (Dicks. ex Fr.)

Paecilomyces spp. Papularia sphaerosperma (Pcrs.) von Hohn. Penicillium atroveneturn Smith P. chrysogenum Thom P. citrinum Thom P. claviforme Bain. P. cyclopium Westling P. frequentans Westling SP. (P. herquei Series) P. jensenii Zaleski P. nigricans Bain. P. olivino-viride Biourge P. raciborskii Zaleski (?) P. soppii Zaleski P. spinulosum Thorn P. thomii Maire Periconia byssoides Pers. ex Schw. Phialophora spp. Pithomyces sp. Scopulariopsis brevicaulis (Sacc.) Bain. Stachybotrys dichroa Grove Stemphylium spp. Stysanus sp. Tnchoderma sporulosum (Link) Hughes T. viride Pers. ex Fr. Trichoderma sp. (T. tawa series?) Trichoderma sp. (crystalline) Trichosponum cerealis (Thum) Sacc. Verticillium nigrescens Pethybr. Verticillium s p p . Vo'olutella ciliata (Alb. & Schw.) Fr. Wardomyces hughesii Hennebert

Brown & Smith

MY XOMYCETES Trichia verrucosa Berk.

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Decomposition of bracken litter