Trees in the ecosystem pt IV: Trees & arthropods

The arthropods are vast in terms of species, and include ants, beetles, butterflies, mites, moths, spiders, and so on. Therefore, covering the entire spectrum of arthropods in this section is impractical, though the general provisioning by trees will be outlined and species will be used to illustrate given examples.

Many arthropods are considered to be saproxylic in nature – they principally utilise dead woody material (both standing and fallen, in both dead and living trees) as habitat, for at least part of their life cycle, though they may also rely upon fungal sporophores associated with the presence of deadwood, as is to be detailed below (Gibb et al., 2006; Harding & Rose, 1986; Komonen et al., 2000). Of all the saproxylic arthropods, beetles are perhaps the most significant in terms of the proportion occupied of total saproxylic species worldwide (Müller et al., 2010), though saproxylic flies also feature in great numerical abundance (Falk, 2014; Harding & Rose, 1986).

Beetles may be either generalist or specialist in nature (on either broadleaved or coniferous hosts), and they will normally require a host with an abundance of deadwood (or large sections of coarse woody debris) usually over 7.5cm in diameter that resides within an area typically not heavily shaded (Müller et al., 2010; Siitonen & Ranius, 2015). This may be, in part, due to many beetle species (in their adult stage) requiring nectar from herbaceous plants, which would be lacking in woodland with significant canopy closure (Falk, 2014; Siitonen & Ranius, 2015). This means that veteran trees amongst wood pasture and parklands (including in urban areas) may be particularly suitable (Bergmeier & Roellig, 2014; Harding & Rose, 1986; Ramírez-Hernández et al., 2014; Jonsell, 2012; Jørgensen & Quelch, 2014), though this is not at all a steadfast rule as species may also be found abundantly in (perhaps more open) woodland, and particularly where there are large amounts of veteran trees and deadwood – around 60 cubic metres per hectare, according to Müller et al. (2010). Granted, they are found particularly in older (mature to veteran) trees, including within cavities that possess wood mould, water-filled rot holes, dead bark, exposed wood, sap flows, fruiting bodies (of fungi and slime moulds), mycelia of fungi, dead branches, and dead roots (Carpaneto et al., 2010; Falk, 2014; Harding & Rose, 1986; Siitonen & Ranius, 2015; Stokland et al., 2012). Beetle species may also not necessarily associate preferentially with a species (or group of species), but with the conditions aforementioned that are present within a tree (Harding & Rose, 1986; Jonsell, 2012). At times, preferable conditions may be an infrequent as one veteran tree in every hundred (Harding & Rose, 1986).

veteran-oak-tree
A veteran oak tree that is of prime habitat for a variety of organisms.

Despite this, species preference is observed. For broadleaved obligates, heavier shade may be more necessary, and in such instances there is a closer affinity of the beetles with fungal mycelium. Because fungi tend to produce more mycelium in cooler and more humid conditions (though this does, of course, vary with the species), the broadleaved obligates may therefore be found normally in greater abundance where conditions are more suited to fungal growth, and their presence may thus be associated with a canopy openness of as little as 20% (Bässler et al., 2010; Müller et al., 2010). This is, of course, not a steadfast rule, and many open wood pastures may support a great abundance of saproxylic beetles (Harding & Rose, 1986).

It is also important to recognise that many species of saproxylic beetle are reliant upon particular stages of the wood decay process. For instance, species that require fresh phloem tissue will only be able to colonise briefly in the first few summers following on from the death of the phloem tissue (Falk, 2014). Other species require significantly-decayed wood in a particular micro-climate, and even of a particular tree species (Harding & Rose, 1986). There also exist intricate associations between species of fungi and saproxylic insects. Inonotus hispidus, which is usually found upon ash, is the habitat for Triplax russica and Orchesia micans, whilst the coal fungus (Daldinia concentrica), also oft found upon the deadwood of ash (Fraxinus excelsior), is the main provider of habitat for Platyrhinus resinosus (Falk, 2014). The birch polypore (Fomitopsis betulina) is also host to numerous species of Coleoptera (Harding & Rose, 1986); as is the polypore Fomitopsis pinicola (Jonsson & Nordlander, 2006; Komonen, 2003; Komonen et al., 2000). This means that these species may be found where there is a suitable population of the fungus’ host species, where sporophores are present and will likely fruit again in the future, across numerous trees, and for many years. Most beetle species rely on oak more so than other tree species however, as oak generally lives for much longer and thus provides a wider array of different micro-habitats, and possesses increased compositional complexity as a result (Harding & Rose, 1986; Siitonen & Ranius, 2015).

ancient_orchard_malus_inonotus_hispidus4
A fruiting body of Inonotus hispidus on apple (Malus sp.). This fungus not only creates habitat in the wood that it degrades but also is a direct habitat through its sporophore.

Therefore, the loss of suitable habitat through active management programmes (including logging, and felling trees for safety reasons in urban areas) will have a very adverse impact upon saproxylic beetles, though also certain species of moth, and even species associated with saproxylic insects, including parasitic wasps, solitary wasps (which use beetle bore holes for habitat), and predatory Coleoptera (Harding & Rose, 1986; Komonen et al., 2000). Curiously, research by Carpaneto et al. (2010) concluded that trees that were ranked as the most evidently ‘hazardous’ were host to the most saproxylic beetle species, and their removal would therefore have a drastic impact upon local populations. Similarly, fragmentation of woodland patches suitable for saproxylic populations has led to a decline in the meta-populations (Grove, 2002; Komonen et al., 2000), as has deadwood removal in a managed site itself (Gibb et al., 2006). Interestingly, though not surprisingly, ‘deadwood fragmentation’ also has an adverse impact upon saproxylic insect populations (Schiegg, 2000).

Both ants and termites also benefit from the presence of deadwood. With regards to both, nests will usually form at the base of a tree or at an area where there is at least moderate decay – enough to support a viable population (Jones et al., 2003; Shigo, 1986; Stokland et al., 2012). Ants and termites both follow CODIT (compartmentalisation of damage in trees) patterns in relation to how their nests progress, and thus their territory will increase as fungal decay propagates further into the host. Ants will not feed on the decaying wood of the host however, and will simply use the decaying site as a nesting area. Conversely, termites will feast upon decayed wood and essentially control (perhaps by slowing down) the spread of fungal decay in a manner that provides as much longevity of the host as possible for a viable nesting site (Shigo, 1986). In tropical rainforests, termites are in fact considered to be one of the principal means of wood decomposition (Mori et al., 2014), and thus the provisioning of deadwood habitat is absolutely critical. Without decaying wood within trees therefore, ants and particularly termites will lack a potential habitat, and thus where a stand is actively managed populations may be markedly reduced (Donovan et al., 2007; Eggleton et al., 1995). Of course, termites are not necessarily to be desired when they are invading the wood structure of a property, and therefore deadwood is not universally beneficial (Esenther & Beal, 1979; Morales-Ramos & Rojas, 2001) – at least, when human properties are involved.

termites_1_007
Ecologically beneficial? Yes. Economically beneficial? No. Termites can – and do – damage timber-frames buildings, as is the case here. Source: Pestec.

The presence of deadwood may also be beneficial for ground-nesting and leaf-litter dwelling spiders, which can utilise downed woody debris (particularly pieces with only slight decay) for both nesting and foraging (Varady-Szabo & Buddle, 2006). In fact, research by Buddle (2001) suggested that such spiders may more routinely utilise downed woody material when compared to elevated woody material (dead branches and telephone poles) because of the greater array of associated micro-habitats, and particularly at certain life stages – such as during egg-laying, for females (Koch et al., 2010). Furthermore, as fallen woody debris can help to retain leaf litter (or even facilitate in the build-up leaf litter), spider populations are more abundant and more diverse in sites where such woody debris is present (Castro & Wise, 2010). Therefore, where woodlands are managed and areas are clear-cut, spider populations may be markedly reduced in terms of the diversity of species. However, generalist species may benefit from the amount of cut stumps (Pearce et al., 2004). Curiously, Koch et al. (2010) suggest that spiders may perhaps benefit from woodland clearance, because the vigorous re-growth of trees and the higher light availability to the woodland floor (promoting herbaceous plant growth) increases the abundance of potential prey. Despite this, old-growth species will suffer (Buddle & Shorthouse, 2008), and thus the population structure of spider populations may dramatically change.

Soil mites are a further group that benefit from coarse woody debris, though also from hollows and holes throughout the basal region of a tree (including water-filled cavities), and from fungal sporophores and hyphae associated with wood decay (Fashing, 1998; Johnston & Crossley, 1993). Typically, termites will use fungi and insects found within the wood as a food source, and the wood structure itself will provide for an array of niche micro-habitats that are critical at different life stages of a mite. Certain mite species are obligates that associate with coarse woody debris exclusively, and may in fact only be associated with certain species’ woody debris. Additionally, mites may utilise woody debris and hollows within trees to parasitise upon other species using the ‘resource’, with both lizards and snakes being parasitised by mites following their frequenting of such resources. Beetles may also be parasitised, though the mite in such an instance may use the beetle as a means of entry into woody debris (Norton, 1980).

It is not just deadwood that arthropods will utilise, however. Foliage, both alive and abscised, is also of use (Falk, 2014). For example, the ermine moth (Yponomeutidae) will rely upon the living foliage of a host tree as a food source, and the bird cherry ermine moth (Yponomeuta evonymella) is one example of this. During late spring, larvae will fully defoliate their host Prunus padus, before pupating, emerging, and then laying eggs upon the shoots ready for the following year (Leather & Bland, 1999). Many other moth species will, during their larval stage, also behave in such a manner and thus defoliate their host – either entirely, or in part (Herrick & Gansner, 1987). Other species may alternatively have larvae mine into the leaf and feed upon the tissues within (Thalmann et al., 2003), such as horse chestnut leaf miner (Cameraria ohridella). Flies, including the holly leaf-miner (Phytomyza ilicis), will also mine leaves in a similar fashion (Owen, 1978). Ultimately however, the same purpose is served – the insect uses the living tissues of a leaf to complete its life cycle, and fuel further generations.

1280px-yponomeuta_evonymella_on_prunus_padus
Bird cherry ermine moth having defoliated an entire tree. Source: Wikimedia.

Fallen leaf litter, as briefly touched upon earlier when discussing spiders, may also be of marked benefit to many arthropods. Ants, beetles, and spiders are but three examples of groups that will utilise leaf litter as a means of habitat (Apigian et al., 2006). Beetles will, for instance, rely upon leaf litter to attract potential prey, though also to provide niche micro-climates that remain relatively stable in terms of humidity, light availability, and temperature (Haila & Niemelä, 1999). Their abundance may, according to Molnár et al., (2001) be greatest at forest edges, perhaps because prey is most abundant at these edge sites (Magura, 2002). Of course, this does not mean that edges created through artificial means will necessarily improve beetle populations, as research has shown that there are few ‘edge specialists’ and therefore populations usually will go into decline where there has been significant disturbance. Unless management mimics natural mortality events of forest trees, then constituent beetle populations may thus suffer adversely (Niemelä et al., 2007).

With regards to ants, Belshaw & Bolton (1993) suggest that management practices may not necessarily impact upon ant populations, though if there is a decline in leaf litter cover then ants associated with leaf litter presence may go into – perhaps only temporary (until leaf litter accumulations once again reach desirable levels) – decline (Woodcock et al., 2011). For example, logging within a stand may reduce leaf litter abundance for some years (Vasconcelos et al., 2000), as may (to a much lesser extent) controlled burning (Apigian et al., 2006; Vasconcelos et al., 2009), though in time (up to 10 years) leaf litter may once again reach a depth suitable to support a wide variety of ant species. However, the conversion of forest stands into plantations may be one driver behind more permanently falling ant populations (Fayle et al., 2010), as may habitat fragmentation (Carvalho & Vasconcelos, 1999) – particularly when forest patches are fragmented by vast monoculture plantations of tree or crop (Brühl et al., 2003). The conversion of Iberian wood pastures to eucalyptus plantations is one real world example of such a practice (Bergmeier & Roellig, 2014).

Also of benefit to many arthropods are nectar and pollen. Bees, beetles, butterflies, and hoverflies will, for instance, use nectar from flowers as a food source (Dick et al., 2003; Kay et al., 1984), and generally (but not always) a nectar source will lack significant specificity in terms of the insect species attracted (Karban, 2015). Despite this, different chemicals secreted by different flowers, and the toxicity of certain nectar sources to particular insects, means certain tree species may only be visited by certain insect species (Adler, 2000; Rasmont et al., 2005). Tree diversity may therefore be key to sustaining healthy insect populations (Holl, 1995), and where species may prefer to frequent herbaceous plant species the presence of a diverse woodland canopy above may still be very influential (Kitahara et al., 2008). This may be because a diverse array of woody plant species increases the diversity of herbaceous species. At times, pollen may also be a reward, as may (more rarely) a flower’s scent. Karban (2015) remarks that all are collectively dubbed as ‘floral rewards’.

References

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Esenther, G. & Beal, R. (1979) Termite control: decayed wood bait. Sociobiology. 4 (2). p215-222.

Falk, S. (2014) Wood-pastures as reservoirs for invertebrates. In Hartel, T. & Plieninger, T. (eds.) European wood-pastures in transition: A social-ecological approach. UK:     Earthscan.

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Fayle, T., Turner, E., Snaddon, J., Chey, V., Chung, A., Eggleton, P., & Foster, W. (2010) Oil palm expansion into rain forest greatly reduces ant biodiversity in canopy, epiphytes and leaf-litter. Basic and Applied Ecology. 11 (4). p337-345.

Gibb, H., Pettersson, R., Hjältén, J., Hilszczański, J., Ball, J., Johansson, T., Atlegrim, O., & Danell, K. (2006) Conservation-oriented forestry and early successional saproxylic beetles: responses of functional groups to manipulated dead wood substrates. Biological Conservation. 129 (4). p437-450.

Grove, S. (2002) Saproxylic insect ecology and the sustainable management of forests. Annual Review of Ecology and Systematics. 33 (1). p1-23.

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Jones, D., Susilo, F., Bignell, D., Hardiwinoto, S., Gillison, A., & Eggleton, P. (2003) Termite assemblage collapse along a land‐use intensification gradient in lowland central Sumatra, Indonesia. Journal of Applied Ecology. 40 (2). p380-391.

Jonsell, M. (2012) Old park trees as habitat for saproxylic beetle species. Biodiversity and Conservation. 21 (3). p619-642.

Jonsell, M. & Nordlander, G. (2004) Host selection patterns in insects breeding in bracket fungi. Ecological Entomology. 29 (6), p697-705.

Johnston, J. & Crossley, D. (1993) The significance of coarse woody debris for the diversity of soil mites. In McMinn, J. & Crossley, D. (eds.) Proceedings of the Workshop on Coarse Woody Debris in Southern Forests: Effects on Biodiversity. General Technical Report SE-94.

Jørgensen, D. & Quelch, P. (2014) The origins and history of medieval wood-pastures. In Hartel, T. & Plieninger, T. (eds.) European wood-pastures in transition: A social-ecological approach. UK: Earthscan.

Karban, R. (2015) Plant Sensing & Communication. USA: University of Chicago Press.

Kay, Q., Lack, A., Bamber, F., & Davies, C. (1984) Differences between sexes in floral morphology, nectar production and insect visits in a dioecious species, Silene dioica. New Phytologist. 98 (3). p515-529.

Kitahara, M., Yumoto, M., & Kobayashi, T. (2008) Relationship of butterfly diversity with nectar plant species richness in and around the Aokigahara primary woodland of Mount Fuji, central Japan. Biodiversity and Conservation. 17 (11). p2713-2734.

Koch, J., Grigg, A., Gordon, R., & Majer, J. (2010) Arthropods in coarse woody debris in jarrah forest and rehabilitated bauxite mines in Western Australia. Annals of Forest Science. 67 (1). p106-115.

Komonen, A. (2003) Distribution and abundance of insect fungivores in the fruiting bodies of Fomitopsis pinicola. Annales Zoologici Fennici. 40 (6). p495-504.

Komonen, A., Penttilä, R., Lindgren, M., & Hanski, I. (2000) Forest fragmentation truncates a food chain based on an old-growth forest bracket fungus. Oikos. 90 (1). p119-126.

Leather, S. & Bland, K. (1999) Naturalists’ Handbook 27: Insects on cherry trees. UK: The Richmond Publishing Co. Ltd.

Magura, T. (2002) Carabids and forest edge: spatial pattern and edge effect. Forest Ecology and Management. 157 (1). p23-37.

Molnár, T., Magura, T., Tóthmérész, B., & Elek, Z. (2001) Ground beetles (Carabidae) and edge effect in oak-hornbeam forest and grassland transects. European Journal of Soil Biology. 37 (4). p297-300.

Morales-Ramos, J. & Rojas, M. (2001) Nutritional Ecology of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) – Feeding Response to Commercial Wood Species. Journal of Economic Entomology. 94 (2). p516-523.

Mori, S., Itoh, A., Nanami, S., Tan, S., Chong, L., & Yamakura, T. (2014) Effect of wood density and water permeability on wood decomposition rates of 32 Bornean rainforest trees. Journal of Plant Ecology. 7 (4). p356-363.

Müller, J., Noss, R., Bussler, H., & Brandl, R. (2010) Learning from a “benign neglect strategy” in a national park: Response of saproxylic beetles to dead wood accumulation. Biological Conservation. 143 (11). p2559-2569.

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Owen, D. (1978) The effect of a consumer, Phytomyza ilicis, on seasonal leaf-fall in the holly, Ilex aquifolium. Oikos. 31 (2). p268-271.

Pearce, J., Venier, L., Eccles, G., Pedlar, J., & McKenney, D. (2004) Influence of habitat and microhabitat on epigeal spider (Araneae) assemblages in four stand types. Biodiversity & Conservation. 13 (7). p1305-1334.

Ramírez-Hernández, A., Micó, E., de los Ángeles Marcos-García, M., Brustel, H., & Galante, E. (2014) The “dehesa”, a key ecosystem in maintaining the diversity of Mediterranean saproxylic insects (Coleoptera and Diptera: Syrphidae). Biodiversity and Conservation. 23 (8). p2069-2086.

Rasmont, P., Regali, A., Ings, T., Lognay, G., Baudart, E., Marlier, M., Delcarte, E., Viville, P., Marot, C., Falmagne, P., & Verhaeghe, J. (2005) Analysis of pollen and nectar of Arbutus unedo as a food source for Bombus terrestris (Hymenoptera: Apidae). Journal of Economic Entomology. 98 (3). p656-663.

Schiegg, K. (2000) Are there saproxylic beetle species characteristic of high dead wood connectivity?. Ecography. 23 (5). p579-587.

Shigo, A. (1986) A New Tree Biology. USA: Shigo and Trees Associates.

Siitonen, J. & Ranius, T. (2015) The Importance of Veteran Trees for Saproxylic Insects. In Kirby, K. & Watkins, C. (eds.) Europe’s Changing Woods and Forests: From Wildwood to Managed Landscapes. UK: CABI.

Stokland, J., Siitonen, J., & Jonsson, B. (2012) Biodiversity in Dead Wood. UK: Cambridge University Press.

Thalmann, C., Freise, J., Heitland, W., & Bacher, S. (2003) Effects of defoliation by horse chestnut leafminer (Cameraria ohridella) on reproduction in Aesculus hippocastanum. Trees. 17 (5). p383-388.

Varady-Szabo, H. & Buddle, C. (2006) On the relationships between ground-dwelling spider (Araneae) assemblages and dead wood in a northern sugar maple forest. Biodiversity & Conservation. 15 (13). p4119-4141.

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Trees in the ecosystem pt IV: Trees & arthropods

New Plant Health Order (2017) – Sweet chestnut blight

A new piece of legislation – entitled Plant Health (Sweet Chestnut Blight) (England) Order 2017 – came into force on 21st February 2017, which relates to the plant pathogen known as sweet chestnut blight (Cryphonectria parasitica).

sweet-chestnut-blight-symptoms-canker
Fungal fruiting bodies surrounding a severe canker (left) and a discernible canker developing on a young stem (right). Source: Forestry Commission.

Applying specifically to England, this Order allows for plant health inspectors (typically of the Forestry Commission) to serve a formal Notice on a site deemed (following official confirmation) to be host to the pathogen (“infested area”) and to identify and serve notices upn surrounding land parcels within the “controlled area” (section 3). In such infested sites that have a Notice served upon them, as detailed in section 4, no movement of Castanea sativa or Quercus spp. can take place within or out of such infested areas without the express permission of a plant health inspector – by a similar nature, susceptible Castanea sativa material cannot be moved within our out from the controlled area. However, such materials can pass through the area(s), assuming the materials do not stop within the area (i.e. the materials are not stored within the area and instead road networks within the area are used to transport the materials further afield). Currently, two demarcated zones exist – both in Devon (here and here).

In addition to detailing the powers provided to the plant health inspector and the categorisation of offences committed under the Order (sections 5 and 6), the Order also refers to – in section 7 – the necessity of a review of the Order. Indeed, the first principal report of sweet chestnut blight must be made by 21st February 2022, and reviews must be more routine occurrences that ensure the Order remains contextual and relevant to the situation relating to sweet chestnut blight’s extent in England.

More information can be found on the Forestry Commission’s web page for sweet chestnut blight – see here.

New Plant Health Order (2017) – Sweet chestnut blight

Fungal foraying in the New Forest

Both a friend and I had the pleasure of trecking around parts of the New Forest with a well-respected mycologist at the weekend. As you can very well imagine, we came across a wide variety of fungi – notably corticioids and polypores. Unfortunately, the poor light levels rendered getting decent photos of corticioids quite tricky (many were on standing hosts), so beyond some rather frequent Amylostereum laevigatum, Byssomerulius corium, Cylindrobasidium evolvens, Schizopora paradoxa and Vuilleminia comedens (which themselves were tricky to get good photos of) there weren’t many other opportunities. Regretfully, I therefore share below some images of poroid fungi and some larger Ascomycetes, though I hope you can nonetheless appreciate the finds!

We’ll start with a really cool find and a find that is my first for the species – the candlesnuff fungus, though not the stereotypical one! In this case, we have the candlesnuff of beech husks, known as Xylaria carpophila. As is evident in the species epithet, it likes to munch away on seed husks. Unlike its companion, it’s also much more slender and harder to spot. Your best shot is to peer into the leaf layer on the forest floor and hunt for some white hairs emerging from between leaves and from exposed husks.

xylaria-carpophila-fagus-sylvatica-husk-1xylaria-carpophila-fagus-sylvatica-husk-2

We now move on to some splendid examples of Kretzschmaria deusta, in both its anamorphic and teleomorphic state. The first set of shots is showing ‘kretz’ tucked neatly within a very tight compresion fork of a large beech, with cambial dieback stretching quite far up the insides of the stems. Certainly a site for future failure! The following images show anamorphic fruiting bodies upon / ajacent to Ganoderma australe (again on beech – note that we were also told that Ganoderma applanatum is genuinely rare in the New Forest, with most finds being Ganoderma australe) and then on the underside of a very decayed beech log and finally a failed end. As both my friend and I remarked, this trip changes our perspective on the fungus, and we now recognise it as an important species in the effective decomposition of decaying wood from – or upon – dead (parts of) the host tree.

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Moving towards the Basidiomycetes, the first set of photos to share is of Ganoderma pfeifferi on – you guessed it – beech! Honestly, this tree species is superb for fungi and probably the best of all native trees as regards to diversity and abundance. Some of the brackets on this beech has at least 20 sets of ‘growths’, suggesting they could be up to 20 years old!

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Rather similar to the Gano is this duo of Fomes fomentarius. On a large dysfunctional lateral of a beech (who would have guessed…!?) that has subsided to the ground, we can see the two sporophores hiding amongst brash.

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To round off (as I’m running out of time to write this post after a busy day at work!) I also share some Phellinus ferreus (now known as Fuscoporia ferrea). I won’t even bother noting the host as you’ll know already, and in both cases the sporophores are upon dead parts fallen from the host. Do note that the fungus also occurs on attached but dysfunctional (i.e. dead) parts of living hosts of species other than beech, too!

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Fungal foraying in the New Forest

A roadside beech colonised by Ganoderma resinaceum

Here’s a nice one! As I was out surveying, there sat this large roadside beech (Fagus sylvatica) that sported a trio of sporophores of the lacquered bracket (Ganoderma resinaceum). Curiously, this association between host tree and parasitic fungus is a not-so-common one in the present day, in comparison to this fungus upon oak (Quercus robur) – in spite of the lacquered bracket historically being more common on beech than any other tree.

Evidently, judging by the past prunung cuts, an arboriculturist made the decision to manage this beech. Whether or not it was due to the presence of this fungus is something open to speculation, though there’s certainly reason to prune this beech once more for good arboricultural reasons associated with hazard management – notably because of the busy road directly adjacent to the beech. A PiCUS test might be the best investigative route of action here, though that decision remains with the landowner.

I’m sure that you’ll be able to appreciate the issue to do with hazard management, from the pictures below!

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To give a sense of context, this is the position of the beech relative to the adjacent road.
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Some rather nice bulging on the main stem, though around the prominent buttress roots we can spot a few sporophores of Ganoderma resinaceum.
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Another fruiting body hides on the other side of the buttress!
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From the damaged bracket atop the one on the right, either we have prior years of fruiting or this bracket was torn off and another one grew in its place earlier during this growing season.
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We can observe how this significant buttress root has likely been produced in response to the white rot associated with the decay incuded by Ganoderma resinaceum.
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And a final picture for good measure!
A roadside beech colonised by Ganoderma resinaceum

Rigidoporus ulmarius acting as a saprotroph

The distinction between a fungal necrotroph (i.e. parasite) and saprotroph is – in the most basic of senses – easy. The former causes the host woody cells to die as the mycelial network metabolises, whereas the latter metabolises woody tissue that has already died / ceased to serve a vascular function. Indeed, this poses an interesting question, by where many fungi on living trees aren’t actually necrotrophs in the truest sense of the word, as they metabolise heartwood that doesn’t serve a function beyond adding structural support to the overall above-ground structure. Consequently, many wood-decay fungi that degrade heartwood, such as Fistulina hepatica, Laetiporus sulphureus and Phaeolus schweinitzii are arguably saprotrophic – even when found on living trees.

Regardless of that entire aspect of fungal ecology (that’s an entire week’s worth of blog posts right there!), the purpose of this post is to share two finds of Rigidoporus ulmarius (the ‘giant elm bracket’) from yesterday. Both were colonising horse chestnut (Aesculus hippocastanum), and specifically dead specimens. For me, it’s an interesting case, as I generally observe this fungus upon living trees, and despite things I have read this is – from recollection – the first time I have seen this fungus on a dead host.

Without further blabbering, I share below the two specimens, which were within 15m of one another. The other horse chestnuts very close by don’t sport outward signs of this fungus, though the localised and elevated inoculum base has probably resulted in all the horse chestnuts acting as hosts for Rigidoporus ulmarius – to varying degrees.

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Rigidoporus ulmarius acting as a saprotroph

Peering inside a failed beech bole

The New Forest has no shortage of failed beech, given the fact that most of the beech are mature or veteran in age. Typically, the species of Ganoderma can be found to be devouring the remaining stumps and stems, though sometimes further fungi pop up in the most unexpected of places. In this case, looking inside the significantly-hollowed bole yielded a sight of various sporophores of the fungus Phlebia tremellosa (known commonly as ‘jelly skin’).

Because this species is considered to be generally be saprotrophic, the extensive decay (which appears to be caused principally by a white rot) wasn’t created by this fungus and was likely generated instead by Ganoderma australe and / or Ganoderma resinaceum. However, upon windthrow of the bole, or perhaps even before that time, spores of this fungus germinated upon the wood substrate and have since produced fruiting bodies. Such structures are also kept snugly within a consistently warmer and more humid microclimate, which has probably ensured they have endured the frosts that covered the outside world in the prior weeks.

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Peering inside a failed beech bole

Roadside Pseudoinonotus dryadeus in abundance

This is only a short post to close-off the weekend, though ideally one that is appreciated – notably, because it showcases the fungus Pseudoinonotus dryadeus in its senescent state and the associated pronounced buttressing employed by the host oak (Quercus robur). I don’t know exactly where this was, though it somewhere along the A371 in one of the villages between the border of Dorset and Somerset through to Cheddar (as if that narrows it down!).

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A sublime crown reduction, no doubt!
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Perhaps this has something to do with it – what came first, the topping or the fruiting bodies? Given the lean on the oak, I admit I don’t actually know. Maybe the pruning wound low down on the right saw a large chunk of the crown removed, enabling for the entrance of fungal propagules and leaving the tree so one-sided?
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Conks of Pseudoinonotus dryadeus litter the central region between two very significant buttress roots, though we can see how the decay extends beyond the strict basal zone. The fibre buckling discernible in the above picture around the location of the fruiting bodies indicates reaction growth, in response to said buckling under the white rot conditions occurring within.
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Tearing off a small fragment of one of the old fruiting bodies, we can see how spiders have used the bracket as a nesting site (assuming the white mass is a spider’s abode for eggs, which I have seen similarly in spent conks of Ganoderma spp.).
Roadside Pseudoinonotus dryadeus in abundance

Fungi everywhere on a single declining beech pollard, New Forest (UK)

I was forunate to be able to spend some time in the New Forest yesterday, having driven back from Somerset after picking up a microscope (more on that, in due time). When last down there, which was during mid-summer, I spent a few hours sojourning around the Bolderwood / Knightwood Oak ornamental drive, with specific focus upon the myriad of mature and veteran beech pollards that dressed the roadside. One beech, even then, alluded to fungal parasitism, given its dire vigour and evident crown retrenchment (perhaps associated with ground compaction, given its close proximity to a car park and the Knightwood Oak). Therefore, I paid a visit to this beech, with the hope of finding some fungi – and I wasn’t disappointed!

I’ll actually be honest and say this beech is testament to the ability for the species to provide for many wood-decay fungal species. I really don’t think I have ever seen a tree more covered in fruiting bodies of many species than this one, and we’ll run through the suspected species below. First, we’ll look at the tree as a whole, however, and from the first image I don’t think there’s any debate over its poor condition. Granted, with the impending demise of a tree, weak fungal parasites and saprotrophs can enter, and this alludes to the cyclical aspect of energy transfer. In time, this beech will be the food for other plants and trees, though for now it’s fungal food.

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I wonder how many more years this beech has before its snatched from the throes of life! Probably not many.
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The arrows relate to the various fungal species found. Working clockwise from the tip of the centre, I spotted what I suspect are Hohenbuehelia atrocoerulia, Chondrostereum purpureum, Mensularia nodulosa (confirmed), Exidia plana and Bjerkandera adusta.
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Here, behind a limb adorned brilliantly with one of the ex-Inonotus species, sit some fresh oysters (Hohenbuehelia atrocoerulea). Evidently, they are free from frost damage, suggesting they are probably only a few days old.
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There’s also a younger set emerging just behind this cluster in the foreground!
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Looking down the main stem, here we can observe how Chondrostereum purpureum and Mensularia nodulosa are inter-mingling. On the whole, it appears the Chondrostereum is more limited in its amassed substrate, if the presence of fruiting bodies are anything to go by – the ex-Inonotus species is abundant on the trunk and further up into some of the limbs.
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In this image we can identify how the two species really do run right up to their respective thresholds.
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For good measure, these are older sporophores of Chondrostereum purpureum. In their juvenile days, they’d have been far more attractive.
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Further round the trunk, we enter the sole territory of the Mensularia nodulosa.
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Angling upwards, the slotted nature of the tube layers becomes very evident.
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Down on one of the buttresses, this witches’ butter (Exidia plana) gets comfy amongst mosses. Note that it’s more likely to be this species of Exidia, as Exidia glandulosa is more often found on oak. To discern between the two however, you’d need to inspect some spores under the microscope.
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Looking more closely one can appreciate (I guess…?) why it’s called witches’ butter.
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And up on another limb, we have what is probably Bjerkandera adusta.
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It seems to be ejoying the decay column from the pruning wound and general dysfunction.
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There’s also some gilled sporophores in this one, which could potentially be Panellus stipticus, though they were too sparse and too small to see properly.
Fungi everywhere on a single declining beech pollard, New Forest (UK)

A wintry visit to Greenwich Park, London

Yesterday, as part of our monthly aim of visiting sites across the south east of England, a half-dozen strong group of arboriculturalists made the journey to London’s Greenwich Park – myself included. Indeed, as much of the park consists of deciduous specimens (principally, avenues of Castanea sativa and Aesculus hippocastanum), the park was rather bare in the foliage sense, though such barren canopies did allow us to appreciate the true magnitude of – most notably – some of the veteran sweet chestnuts. The frost-clad ground and crystalline sky provided a similar beauty, and thus we shall begin with one of the most iconic vistas from Greenwich Park – the city skyline.

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As we stood adjacent to the observatory, we could admire – amongst the furor of tourists and scout groups – the sightly perverse beauty of a city. I say perverse, as such artificial and polluted landscapes don’t tend to suit those who don’t consider themselves urbanites, which includes myself.

Of course, we didn’t go there for the view, so let’s get into the main bulk of this account – trees and fungi. There’s no real order to how the below series of images rank, so don’t consider this post a chronological reflection of our trip!

Perhaps the best place in which to start the core section of this post are the huge sweet chestnuts, though we must begin on a rather sombre note. With a species of Phytophthora suspected on site and some of the older individuals exhibiting stunted and chlorotic leaf growth, there is a valid concern for the future of these veterans which is – without doubt – highly concerning. During the winter months, fully appreciating this contemporary issue is difficult, though we did spot some foliage on the floor that was certainly smaller in size than would be typically expected. Alas, this situation should not impact adversely on our admiration of these trees, and should in fact raise attention and draw intrigue to those within the industry and beyond, with an eye to ensuring we continue to care for the current and future populations of veterans. Therefore, promoting the Ancient Tree Forum and their most recent publication on ancient and veteran tree management is critical. And now, for some fine shots of various veterans!

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This veteran sweet chestnut was the first one to greet us as we entered the park from the southern end. Not a bad induction!
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As the city blocks paint the skyline to the right, we get a brilliant juxtaposition between the historic and the contemporary. In such a dynamic and ever-changing landscape such as London, this veteran sweet chestnut acts as a vestige of the old.
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From another angle, the same sweet chestnut as above’s form can be more greatly appreciated. The helical patterns of the wood fibres and bark are as if they have been wound like rope.
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This veteran has seen better days, though still stands proudly by the cafeteria. The ground beneath is woefully compacted, which must be having an impact upn the tree’s ability to function as a living being. Unlike the two shown above, it also doesn’t have a layer of mulch applied around its rooting environment.

Some of the veteran sweet chestnut we came across were also home to two annual common wood-decay fungi – Fistulina hepatica and Laetiporus sulphureus. Without doubt, the state of the fruiting bodies was not good, though when ravaged by time, wind, rain, frost and sun, to still even have a form is respectable! Certainly, a summer visit would have yielded a much greater haul of these two fungi on the sweet chestnuts, so a summer visit is probably on the cards.

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One of Greenwich Park’s many veteran sweet chestnuts with an added extra – a small and rather weathered…
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…you can see it…
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…Fistulina hepatica! Picked off by parasitism before it reached a respectable stature, it still nonetheless produced a hymenium and thus likely produced spore.
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A second sweet chestnut, this time slightly smaller, but again with Fistulina hepatica.
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The state of it is, however, diabolical!
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A smaller and thus younger sweet chestnut, in this instance.
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It sports a fungal fruiting body, nonetheless!
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A chicken of the woods, which is beaten and bruised.
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Another smaller sweet chestnut, and another Laetiporus sulphureus.
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Note how it emerges from behind a bark-covered area.
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Again this sporophore is long beyond its best, though retains a little more dignity in the face of its impending crumble.

Away from the sweet chestnut, there was a variety of other large trees. Below, I share the ones that were home to fungi, through the identification of fruiting bodies. Absolutely, all trees on site are host to many species of fungi, though fruiting is not necessary in many instances, and it certainly costs the fungus energy to create and sustain. To begin, we’ll take a look at the ever-accomodating mature Robinia pseudoacacia in the park, which didn’t disappoint. In all, the population supported three species of wood-decay polypore, as we will see in the below images.

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A very mature false acacia, with a very mature Laetiporus sulphureus fan on the main stem.
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Well, sort of a fan – the remains of!
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I imagine someone yanked this off, as it looks like a rather clean break.
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Very close by, a second false acacia cradles another Laetiporus sulphureus.
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Here, we can see how it’s at the base of the main stem, in place of higher up the structure.
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This second one is far worse for wear!
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A double-stemmed Robinia pseudoacacia, which was once at least triple-stemmed.
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At the base, a senescent Perenniporia fraxinea and a cluster of broken active sporophores can be seen.
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For good measure,here’s a better look at the entire bunch.
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It’s a little disappointing that the fruiting bodies have been damaged, though that doesn’t stop them being Perenniporia fraxinea!
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And a second example of Perenniporia fraxinea on this false acacia, too.
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Right at the base, to the left.
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This one appears slightly different to how it’d usually look (it’s not photogenic!).
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Regardless, a showing of the trama reveals it as Perenniporia fraxinea.
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It looks like the park managers are aware of the decay on this Robinia, as it has already been pruned!
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If you look between the buttresses and into the basal cavity, you can spot a single Ganoderma australe. More were on the other side of the tree, though were old and worn.
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With the sun behind the camera, this southern bracket looks rather pretty.

Steering attention away from false acacias, I now turn towards a focus on the brown-rotting polypore Rigidoporus ulmarius. With both horse chestnut (Aesculus hippocastanum) and beech (Fagus sylvatica) on the site, the chances are that there would have been a few examples of this fungus. Indeed, there were, as we will observe.

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This first example, on horse chestnut, is an interesting one.
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It’s the return of the cavity-dwelling Rigidoporus!
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Away from the wrath of the elements, this sporophore doesn’t have the algal green stain atop and bathes in its own substrate.
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A cutting identifies this specimen as Rigidoporus ulmarius, with the cinnamon tube layer and brilliantly white flesh.
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The second horse chestnut sits in line for the toilets, patiently waiting for soneone to give it the 20p needed to get beyond the toll gate.
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If you want, you can even sit down to inspect this tree!
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This might well be this sporophore’s first season. I wonder how many more years it will see before it gets knocked-off or is aborted.
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Half way up this steep hill, a beech stands seemingly without significant issue.
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Oh, wait – here’s the issue!
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Is that a shade of green?
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From this shot, it looks most probably like Rigidoporus ulmarius. If so, we have two examples in one site of its cavity-dwelling abilities!

Greenwich Park also has a good number of large plane trees (Platanus x hispanica). The most abundant fungus on these trees was massaria (Splanchnonema platani), and there probably wasn’t a plane in the park that didn’t show at least some signs of its presence. However, it was the large plane with Inonotus hispidus that gained much of my eager attention, given I am not often around mature planes with extensive fungal decay.

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A rather lofty plane tree.
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As the crown breaks, we can spot a single Inonotus hispidus sporophore.
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Whether there is an old wound at or around this site is hard to say, though for this fungus to be able to colonise one would expect so.
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Perhaps an old branch stub above the fruiting body?

To round this post off, which has admittedly taken a long time to write, I’ll share some lovely images of a not-so-lovely bird – the parakeet (Psittacula krameri). Plaguing many of London’s parks and beyond, these things produce an utter cacophony and are certainly invasive, though one must admit that they are incredibly photogenic. Below, I share a few examples of where the parakeets were using cavities for shelter.

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A horse chestnut monolith, seemingly vacant.
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Wrong! Enter the parakeet(s).
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This one stands proudly atop a pruning cut.
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Along a plane tree branch, this parakeet appears to be guarding its abode.
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“Oi m8, w0t u lookin’ @???”
A wintry visit to Greenwich Park, London

Winter wood-decay fungi

The weather has been quite superb over the past few days, and I utilised my lunch break today to get out and explore a country park I visit probably once every month or two. Unfortunately, it’s pretty massive, so covering the entire place takes far longer than a single hour, though that doesn’t dissuade as there are still fungi to find – and fungi I did find.

The title of this post, I’ll admit, is a little devious. Yes, it’s winter, and yes, these are fungi, though some are perennial polypores that essentialy cheat the system a little. Worry not, however, for there are a few examples of annual fungi thrown in for good measure. Regardless, the mix found today was pretty decent, and a few of those species shown below aren’t ones I come across very often.

We’ll begin with Perenniporia fraxinea, which I found on two different ash within very close proximity to one another. The second example is easily the best, as some of the brackets were absolute monsters (though it was the smaller ones that drew my attention to them). Sadly, due to the strong sun and the sheer mass of bramble and bracken surrounding the ash, getting good photos was incredibly tough, though the ones beneath are suitable enough to offer a sound appreciation of their size. If you look hard enough, you’ll undoubtedly find similar-sized examples, as they aren’t too difficult to track down if you know where there are plenty of large and mature ash. The first example is still useful, however – it demonstrates how variable the morpohology of the species can be.

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Interestingly, the first example of the above Perenniporia fraxinea yielded another treat – Coriolopsis gallica, atop. From what I have seen of this fungus, it tends to favour ash (Fraxinus excelsior), though as it isn’t one I see that often it might simply be a bias from my observations – ash are, around here, abundant, and there is no shortage of wind-damaged ash and fallen limbs adorned with fungi. Relatively nearby, another ash, in the form of a fallen limb, supported a separate colony (or colonies) of this species, and both examples are thus shown below.

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Essentially adjacent to the second example of Coriolopsis gallica stood a large hornbeam (Carpinus betulus), which had a longitudinal section of cambial dieback tracking its main stem from the death of the branch above. Despite not being at all uncommon, along this area of dieback were multiple sporophores of the fungus Ganoderma australe.

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And finally, right at the top of another ash (which also was dressed with Inonotus hispidus) sat what appeared to be Pleurotus ostreatus – albeit, very mature. Exhausting my camera’s zoom lens, the below photos were captured. Given the position, size and colour of the fruiting bodies, I doubt it could be anything else.

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Tell a lie, there’s actually one more series of shots to show. This time, we have an oak (Quercus robur) that has fallen and since reiterated to form a new crown, courtesy of phototropism. At the cusp of the transition between functional and dysfunctional wood stood this rather tiny little sporophore, blue in colour. From my experience and knowledge, I would suggest that this is Postia subcaesia, which is a species of the genus Postia that is routinely found on deciduous trees – most species are largely found on gymnosperms, however.

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Winter wood-decay fungi