Having been informed earlier by a friend that they have an article coming out soon in the journal Field Mycology and having then read the article, I considered it important to build on the information and photos shared in the manner I am most familiar: ramblings. I do not want to spoil the article so please do source the article yourself, though as a form of executive summary, this fungus, Confistulina hepatica, is the anamorphic (asexual) stage of the fungus Fistulina hepatica (beefsteak), which is common on oak and sweet chestnut. I have found it once on beech, though it generally sticks to the first two hosts. This anamorphic stage produces asexual spore, which adorn the fruiting body’s outer portion in abundance. The reason for its emergence is not known, though it might be weather-related. More information is absolutely required from across its host range – not just England!
Disclaimer: The older finds, because I didn’t know what I was looking at, are quite poor photographs. A huge shame, but alas!
Disclaimer 2: I suspect many of these are the anamorphic stage Confistulina hepatica, though none were confirmed so please do not assume they all are. This blog post is simply to begin building a knowledge base that builds of the limited resource pool of present.
The first oak that I’ll share is perhaps one of the more interesting of the bunch because, two years in a row (2015 and 2016), the outwardly anamorphic fruiting body appeared in the same location; albeit, in 2015, the fruiting body was larger. Nonetheless, it infers that, in a crude manner, the same mycelial colony has done the same thing two years in succession. Unfortunately, during 2015, I didn’t get a shot of the whole tree so the location of the arrow points to the 2016 occurrence. However, from the positioning of the ivy, we can see the location is the same.
The next series of shots were taken on my mobile phone back in 2015 and again from oak. Once more, the adornment of the fruiting body with exudations, of which some are darker, can be observed. 2016 saw the fungus return, with a vengeance, and in a different position, again, an anamorphic fruiting body.
From here, we go to another 2015 find. This time, the fruiting body was a little elevated on the oak and evidently emanating from an area of burring / accumulation of dormant buds beneath the bark surface. This one quickly became senescent after perhaps a week so whether it’s Confistulina or not is tough to say – I include photos of both times I visited it. It did not reappear in 2016.
The remainder of the photos take us into 2016 and most (but not all!) are taken with a better camera, which is good! First, we venture down to the New Forest and look at a well-decayed oak log, upon which a cluster of fruiting bodies sit atop the log.
The next series are taken a month apart (late August and late September). What’s curious with this one is that we can see two anamorphic fruiting bodies and, come September, Laetiporus sulphureus fruiting directly alongside. The host, as can be seen, is oak, which is in a hedgerow of oak and ash.
Now, we move to a curious case of two fruiting bodies next to one another, again on oak, where one became a teleomorph and the other an anamorph. Why? Who knows. Very interesting, however, as I am sure you can appreciate.
In October of 2016, I came across this majestic oak in a field. On a buttress root was what appeared to be an anamorphic fruiting body of Fistulina hepatica, which we can observe below.
Lastly, here’s one I suspect on sweet chestnut. I didn’t return to check how it did, though this year I’ll certainly keep more of an eye out and be more thorough in my inspections of the samples! Please share any examples you might have found of this, too – it’s important we build up a knowledge base.
Nothing much need be added, in light of who is narrating. As a 20-minute long film, it’s something you can readily watch at any point where you have some time going spare. There’s a few good segments on trees, including on ancient trees, deer, deadwood and wood-decay fungi. Really a fascinating watch!
As has been highlighted previously in this blog (the series on state forestry, for example), trees have been used to fund the gluttonous cogs of the war machine, across both time and space. Usually, this timber consumption has manifested from the progressive land acclamation and legislatory enforcement by the state, until large tracts of forest are state-owned; or private forests can be utilised by the state in times of political emergency. This post therefore focusses not on repeating what has previously been discussed, and instead investigates how the forests themselves have been used for the arts of war – as in, the forest as a site of battle, or for the preparation of one; not that the forest as a site of battle is to be desired, for any attacking force must expect the unexpected, and typical formations and approaches to warfare cannot be applied in the enclosed forest setting (Clayton, 2012). Of course, the prior blog posts I did on state forestry highlight how armed guerrillas in Indonesia and Zimbabwe used the forests for cover and ambush, though this aspect of forest use extends far beyond just these two examples.
Beginning somewhat close to home (for the author), it can be recognised how the New Forest, in the county of Hampshire, UK, was used by the British and American armies, during the Second World War (Leete, 2014). Because of its strategic location relative to the coast of continental Europe, residing along the south coast of England, and complete with nearby ports in Southampton and Poole, the New Forest was used as the first line of defence against any invading Germans coming over from France. For this reason, the forest was used by both the Intelligence Service, and also by thousands of troops who would constitute the defending force if enemy ground invasion did occur. Furthermore, the extensive forest cover provided camouflage for over 30,000 troops in the moths before D-Day (Operation Neptune) in 1944, and the surrounding heathlands acted as airfields and storage areas of military vehicles. In total, 20,000 acres of the New Forest were utilised by the resident forces, during the war, though much like how the forest suddenly filled with troops it also quickly emptied, and almost immediately after the D-Day landing at Normandy the New Forest once again became very sparsely populated.
The Second World War, beyond its association with the New Forest, was the site of actual battle. One example is that of the Battle of Hürtgen Forest, which took place between the US and German forces through September 1944 to February 1945. Situated on the border of Germany and Belgium, the Germans occupied the forest because of its strategic importance to future offensives on the Rhine. Fearing that these German troops would eventually therefore support the front line, the US Army sought to take control of the forest to stall this pursuit. However, because the terrain was very uneven, the access routes through the forest to constituent villages were narrow and almost non-existent, the trees were very dense in many locations, and forest clearings sudden and sporadically occurring, support from tanks was not feasible, and navigating the forest was often challenging and certainly very risky. Subsequently, the US forces suffered losses of over 30,000 men (at times, entire units were lost), eclipsing those incurred by the Germans; in spite of their much larger size. Granted, the Germans also suffered huge losses (Rush, 2001). The forest was thus named ‘The Death Factory’, by the US troops (Whiting, 2000), and became the grave of many individuals from both sides of the conflict.
Curiously, the close of the Second World War also saw forests treated almost as bounty or reparation; at least, in Germany. Following the defeat Germany suffered, the country was subsequently segmented into various zones: the south-west of Germany became the French Zone, whilst the southern and south-east segments were under control by the Americans, the northern and north-west overseen by the British, and the east and north-east by the Soviets. The purpose of this was to enable Germany to ‘repent’ its ‘sins’, and the occupiers – the Americans, British, French, and Soviets – could harvest the forests as they saw fit, as long as such harvests were not in excess of the reparation quotas detailed after the Potsdam Conference in the summer of 1945.
Unfortunately, as such quotas usually were far greater than the rate at which the remaining forests (many were in an alarming state of disrepair, commercially-speaking) of Germany could be replenished, the Soviet zone saw fourteen years’ worth of timber logged in just four years. Alongside the purging of these now Soviet-controlled forests, those foresters who were not drafted into the war effort by the German government at the time were forced to work as hard labourers in the forests, and the traditionally scientific method that was German forestry was quashed by the inexperienced Soviets. Similar unsustainable levels of forestry were undertaken in the other occupied areas of Germany, by the Allied governments (Nelson, 2005).
Beyond the Second World War, Clayton (2012) remarks that the forest has been the site of battle as early as 9 A.D. In this year, the forest of Teutoburg was to plague three Roman legions and their auxiliaries – who were ambushed by the allied local Germanic tribes after an uprising in the region – quite cataclysmically. In this case, the Roman legions were headed by the reportedly inexperienced commander Publius Quinctilius Varus, whilst the commander of the allied tribes was the Germanic nobleman known as Arminius, who had himself been trained by the Roman army and was in fact part of the Roman legions who were tasked to deal with the uprising of the local tribes, though quickly defected to lead the Germans into battle.
Under the order of Varus, who was persuaded by Arminius (who at this point in the saga was still in the Roman army and appointed as an officer), the Roman legions headed into the forest to attempt to quell the uprising; at which point Arminius defected, and gathered up to 50,000 Germans to fight against approximately 7,000 Roman troops and their horses (including the three legions of eighty men each). In this forest, the now-defected Arminius used the terrain (including steep slopes, fallen trees, and dense forest cover) to confuse and disorientate the armour-clad Roman legions and support troops, who at first became surrounded and then were torn apart by the nimble Germanic warriors equipped with lightweight weapons (such as darts) and, for close combat, broadswords and spears. Most Roman troops were killed within the forest, in the small units that fled in all directions after Varus (who committed suicide) declared a retreat, though some unfortunate individuals were enslaved and / or tortured by the Germans. Ultimately, this situation manifested because the Roman troops were geared for close combat in the open setting, and the clever use of the forest by Arminius and his warriors led to what can only be considered a Roman tragedy – a tragedy that would not have occurred, and in fact likely have been reversed, if the battle was undertaken in the open (Clayton, 2012; Murdoch, 2006).
The use of trees during conflict has also given rise to their use for hanging and other forms of execution (Stone, 2008). Certainly a macabre aspect of how warfare – and on a broader scale acts of genocide – ties man to the arboreal world, it is nonetheless an important point to consider, as it highlights how the tree, as a tool, has uses that extend beyond those aforementioned. In the genocide that plagued Cambodia from 1975-1979, for instance, the Khmer Rouge, who were followers of the community party led by Pol Pot, are said to have thrown children against trees until they died – because trees were cheaper than bullets. In these cases, Tyner (2009) remarks, the children were executed because their parents were considered enemies of the state. Lynching in the US, between 1889 to 1930, constitutes another form of warfare; albeit more a form of societal warfare, which can occur even during peacetime. During this period, an estimated 3,724 individuals were lynched, and before usually being hung from a tree and displayed for all to see the pursued individual was tortured, humiliated, dragged, and sometimes burned in front of potentially many thousands of onlookers (Dutton, 2007). In the UK, trees have also been the site of hangings; for example, for the execution of ‘rebels’ – whatever this loose term was deemed to define at the time by the ruling powers (Barnes & Williamson, 2011).
Running concurrently to the very human dynamics of wars and forests, exist more ecologically-based aspects worthy of consideration in this section. Principally, and notably over the past decades, one can identify the desire to safeguard forest biodiversity during times of war, by incorporating forest conservation into military projects (Machlis & Hanson, 2008). As ascertained prior to this point, the demands placed upon the forest in such a period unrest is possibly incredibly great, and particularly when the forest is being harvested for its timber, is being cleared to flush out a hiding enemy or to remove a hiding place, or the war is taking place largely within the forest (Reuveny et al., 2010). In recent years, tropical forests over South America and Africa have been the site of armed conflicts between the state and drug cartels, rebels, or otherwise, and McNeely (2003) astutely observes that such forests and their ecosystems can therefore be considered victims of war. Where these forests are considered hotspots for biodiversity, the impact is certainly markedly more severe and concerning for the scientific community (Hanson et al., 2009).
However, war is not always bad for forests. Where armed conflicts drive the general populace away, if the forests are not being actively utilised for resource to fuel the conflict, then they can undoubtedly benefit from the sudden drop in human pressures. Of course, the displaced populace is not purged from existence, and therefore where refugee camps associated with the conflict are constructed within – or adjacent to – forests, there can be a huge spike in deforestation. A pertinent example of such a phenomenon is when the Rwandan civil war displaced large numbers of people, who settled in the Democratic Republic of Congo in refugee camps and caused over 300km² of deforestation to nearby forests (Machlis & Hanson, 2008).
With the weather remaining fair, in spite of the onerous musings spouted from the verbal orifices of the meteorological office, getting out at the weekend to explore new sites is still very much on the cards. Today, a group of us went over to Aldenham Country Park in north-west London, to search for interesting fungi on trees; as if a weekend would yield any other result!
We started the day by doing something socially reprehensible: bringing in fungi collections for display. As the below photos show, my collection is growing in extent, though is dwarfed in literal size by another collection, which essentially involves monster brackets that are, in some cases, still clinging to the very substrate that provided them with their life.
Before sharing some finds from today, it’s almost important to share some images of more cross-sectional decay as caused by Ganoderma pfeifferi. For those of you with a memory that stretches back beyond a mere seven days, you might recall a recent post I made showing a decay cross-section on a failed beech. Below, we see how the fungus’ activity within a branch stub of a beech has resulted in zonal decay, which is somewhat comparable to the other example shared recently – particularly, with regards to the rosing pattern.
And so, on with the walk we did, quite early on we wandered past an old poplar stump with some quite extensive Rigidoporus ulmarius decay. Indeed, as is quite routine with this fungus, the internal hollow was clad aplenty with small brackets, whilst the outside sported a much more sizeable fruiting body still in an active phase of its existence. Evidently, a new hymenium has recently been laid down, suggesting that this fungus is soon ready to begin producing spore for the coming season.
Very soon after this sighting, a fallen poplar log with Oxyporus populinus was discovered. I admit to only having seen this fungus twice, of which this find was one, so for me this was particularly exciting. In fact, the single fruiting body was rather massive and easily discernible by the quite brilliant tube layers separated by narrow bands of mycelium. Almost directly adjacent to this was a fruiting body of Ganoderma applanatum, as could be determined morphologically by the very thin cuticle atop the bracket (that is crushed easily and cuts very easily) and the extensive damage to the fruiting body, as caused by the yellow flat-footed fly Agathomyia wankowiczii.
Following the sighting of copious amounts of Daedaleopsis confragosa, our attention was then drawn to a rather sorry-looking beech tree over a well-used footpath. Upon close inspection, both Kretzschmaria deusta and the rhizomorphs of Armillaria mellea could be found, which certainly puts the longevity of this beech as is into doubt. To be honest, in all likelihood it’ll be monolithed, in order to still provide habitat but with the risk removed.
Around the proverbial corner (it was more like a ten minute trundle) from this beech stood a massive stump of an old poplar. In its prime, this would have been a tree operating on beast-mode, though is now far more modest in size. However, to make up for its literal demise, it now is host to the fungus Trametes gibbosa, which can be seen around one of the two stems.
Delightfully, this stump also housed a bird nest, which I found only by pure chance when noticing what looked like chocolate mini-eggs! Tucked away impossibly well within a bark crevice was a small robin’s nest (I think), complete with four eggs. Hopefully, this stump will offer enough privacy to enable the chicks to develop well and not get picked-off by predators.
Once we had come across yet more Daedaleopsis confragosa, which I was busy photographing, a friend spotted a single Sarcoscypha coccinea (scarlet elf cup). Somehow, this is the first time I have seen this fungus and I can understand why it’s such a popular one! An absolute gem.
And then came something I found very interesting: my first ever sighting of the fungus of willow known as Phellinus igniarius. Upon what was either a crack willow or white willow, a few fruiting bodies had grown and the decay had since led to failure of an upper limb, which has since been cut up and left on the ground. The resulting abundance of fruiting bodies on both the tree and sawn logs is a testamenrt to the extensive colonisation of this fungus within the host. The largest bracket, which was a casulaty of the failure, in fact did not senesce and instead reiterated its growth so that the hymenium and tube layer re-grew at an angle perfectly parallel with the ground (known as geotropism / gravitropsim).
To round off, I share a diabolically grotesque example of Ganoderma resinaceum upon Turkey oak. Enough to challenge the gargoyle statues of various catacombs (in both video games and real life, if there exist any!) for the prize of what’s the most vile in appearance, and we’re not talking about the Turkey oak here, this fungus is clearly a shadow of its former self. Nonetheless, it is important we can still identify them in such aberrant form, if we are to appropriate diagnose issues and enact management regimes. Thus, as a sort of encore, I present to you…
Single-celled organisms that may create larger structures as groups in order to reproduce, slime molds, whilst not considered active wood decayers, can be found colonising deadwood (Heilmann-Clausen, 2001). Deadwood of 10-22 years of age, Heilmann-Clausen (2001) alleges, is most optimal for slime molds – at least, for the species observed on the decaying beech logs that featured within the study. This correlates with current understanding of slime molds, which suggests species strongly prefer moist, well-decayed wood.
The presence of wood-decay fungi sporophores, or even simply mycelium within the wood substrate, may also act as a source of energy for slime molds (Ing, 1994). As mycelial networks and their associated sporophores may take some time to develop within deadwood, this may perhaps be a further reason for why slime molds are found in greater abundance on older woody debris. The presence of bacteria, also greater in abundance on older and heavily-decayed wood, may also influence slime mold presence, as bacteria can be utilised as a further source of energy (Heilmann-Clausen, 2001). Lodge (1997) describes some slime molds as “predators of decomposers”. Slime molds may also utilise decaying leaves as a habitat (Ko et al., 2009; Raper, 1941; Raper, 1951; Stephenson, 1989). Therefore, the decaying leaf litter-soil ‘zone’ is another potential niche for slime mold species (Landolt & Stephenson, 1986). Moreover, slime molds may be found upon the bark of living trees (Olive & Stoianovitch, 1973; Stephenson, 1989).
Away from wood, decaying leaves, and soil exclusively, the composition of a forest ecosystem may also have an impact upon slime mold density. Landolt et al. (2006) found that, whilst species diversity did not differ between deciduous-broadleaved and coniferous stands, the broadleaved sites were host to slime mold populations over four times more abundant than coniferous sites. The same study also identified that different species of slime mold would be found at different altitude levels within forests, and suggested different micro-habitats perhaps act as refugia for different slime mold species that may have once colonised greater ranges of forest.
Heilmann-Clausen, J. (2001) A gradient analysis of communities of macrofungi and slime moulds on decaying beech logs. Mycological Research. 105 (5). p575-596.
Ing, B. (1994) Tansley Review No. 62: The phytosociology of myxomycetes. New Phytologist. 126 (2). p175-201.
Ko, T., Stephenson, S., Jeewon, R., Lumyong, S., & Hyde, K. (2009) Molecular diversity of myxomycetes associated with decaying wood and forest floor leaf litter. Mycologia. 101 (5). p592-598.
Landolt, J. & Stephenson, S. (1986) Cellular slime molds in forest soils of southwestern Virginia. Mycologia. 78 (3). p500-502.
Landolt, J., Stephenson, S., & Cavender, J. (2006) Distribution and ecology of dictyostelid cellular slime molds in Great Smoky Mountains National Park. Mycologia. 98 (4). p541-549.
Lodge, D. (1997) Factors related to diversity of decomposer fungi in tropical forests. Biodiversity & Conservation. 6 (5). p681-688.
Olive, L. & Stoianovitch, C. (1974) A cellular slime mold with flagellate cells. Mycologia. 66 (4). p685-690.
Raper, K. (1941) Dictyostelium minutum, a second new species of slime mold from decaying forest leaves. Mycologia. 33 (6). p633-649.
Raper, K. (1951) Isolation, cultivation, and conservation of simple slime molds. The Quarterly Review of Biology. 26 (2). p169-190.
Stephenson, S. (1989) Distribution and ecology of myxomycetes in temperate forests. II. Patterns of occurrence on bark surface of living trees, leaf litter, and dung. Mycologia. 81 (4). p608-621.
Some say it’s written in the stars, though the only experience I have had with braille is from select old Nintendo games from the 1990s and early 2000s (revealing my age a little here!). Others say it’s just annoying. I’d probably agree with the latter! Regardless, here we have it: more pictures of fungi on trees.
As always, I keep my eye out for some interesting finds. This week has been pretty decent on the fungal side of things, though given the time of year only the perennial polypores are really observable – asides from the odd Flammulina velutipes / elastica and some enterprising Pleurotus species. Nonetheless, for the sake of showcasing unique finds and for educational purposes, here are a few species of polypore and some common agarics.
Firstly, we have a rather cool deck of Ganoderma resinaceum brackets around a rather pronounced buttress on an oak (Quercus robur). The fruiting between the two buttress roots is likely indicative of good reaction growth that is well-compartmentalised, which in turn infers respectable and probably sound (i.e. free of appreciable decay) buttressing from which the oak is supporting itself. We then have some shots of a rather aberrant duo of Trametes gibbosa on what is probably an old sycamore (Acer pseudoplatanus) stump, some Kretzschmaria deusta on (again!) sycamore, Ganoderma australe on a fallen ash (Fraxinus excelsior) and finally some Flammulina sp. and Pleutorus ostreatus on a very decayed stump of an unknown deciduous broadleaved species.
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).
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).
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.
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.
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’.
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