As I was trawling the depths of the Oxbow Books store, which is an utter treasure trove of books on various matters (many pertain to trees, hedgerows, gardens, woodlands, forests and the broader concept of landscape ecology – notably from the imprint Windgather Press), I came across a new book, to be released later this year, by Mark Johnston, the author of Trees in Towns and Cities: A History of British Urban Arboriculture.
So what is the title of this book? If you paid attention to the title, you’d already know, though for the sake of clarification it’s Street Trees in Britain: A History. As regards a description of the text, taken from the publisher’s page:
“The trees which line many of the streets in our towns and cities can often be regarded as part of a heritage landscape. Despite the difficult conditions of an urban environment, these trees may live for 100 years or more and represent ‘living history’ in the midst of our modern streetscapes. This is the first book on the history of Britain’s street trees and it gives a highly readable, authoritative and often amusing account of their story, from the tree-lined promenades of the seventeenth century to the majestic boulevards that grace some of our modern city centres.
The impact of the Victorian street tree movement is examined, not only in the major cities but also in the rapidly developing suburbs that continued to expand through the twentieth century. There are fascinating descriptions of how street trees have helped to improve urban conditions in spa towns and seaside resorts and also in visionary initiatives such as the model villages, garden cities, garden suburbs and new towns.
While much of the book focuses on the social and cultural history of our street trees, the last three chapters look at the practicalities of how these trees have been engineered into concrete landscapes. This includes the many threats to street trees over the years, such as pollution, conflict with urban infrastructure, pests and diseases and what is probably the greatest threat in recent times – the dramatic growth in car ownership.
Street Trees in Britain will have particular appeal to those interested in heritage landscapes, urban history and the natural and built environment. Some of its themes were introduced in the author’s previous work, the widely acclaimed Trees in Towns and Cities: A History of British Urban Arboriculture.”
Retailing at £30, you can currently pre-order it for £22.50, which seems like a relative steal. I would strongly recommend that, if you are to pre-order it, you do so via the publisher here, which supports them directly and will enable them to continue to press more books of a similar nature. At the very least, they’ve got a pre-order through me, though given many who frequent this blog are from the United Kingdom, I hope they’ll receive more interest (I’m sure they will!) prior to the book’s publication.
Trees, and more specifically groups of trees, are of significant importance to avifauna. Their provisioning of food, either directly (fruits, nuts, blossom) or indirectly (attracting insects and other types of prey), in addition to their ability to act as a nesting site, roosting site, or otherwise, makes tree presence absolutely crucial to a successful and healthy bird population. Of course, different bird species will respond favourably to different tree species and stand structures, and this – amongst other aspects – is discussed below.
As alluded to above, the structure of a woodland stand will have a marked impact upon bird species present within a site. For example, active coppice woodlands will provide habitat to bird species not frequently (if at all) found in old-growth stands or even coppice of over 11-12 years since the last cycle (Fuller & Green, 1999), though wood pastures, forest glades, and even agricultural fields bordering woodland may provide niche habitat for particular birds, of which many may be associated with grasslands and the transitional zone (ecotone) between grassland and woodland (Costa et al., 2014; Hartel et al., 2014; Hinsley et al., 2015) – including the nightingale (Luscinia megarhynchos) and the chiffchaff (Phylloscopus collybita), in the UK.
A nightingale perched upon a tree branch. Source: Wikimedia.
Stand structure will also impact upon the growth of young chicks, with some species growing better in older stands and others in younger stands (Hinsley et al., 2002). This is due to some bird species feeding up in the crown of a tree, whilst others forage near to ground level. For ground foraging birds, there will likely be a lack food sources available, where canopy closure has occurred; as will there be a lack of ground-cover for nesting (Fuller & Green, 1999). Similar conditions can however be created by grazing mammals, with deer being a notable example in the UK and North America (Gill & Fuller, 2007; McShea & Rappole, 2000). Furthermore, ground-nesting and ground-foraging birds are also more sensitive to disturbance, and therefore their presence may also be limited in high-traffic areas and locations where predators (and herbivores – including deer and other grazing animals) are found in abundance (Ford et al., 2001; Fuller, 2001; Martin & McIntyre, 2007; Schmidt & Whelan, 1999). Vehicular traffic may also be an issue, and notably when a woodland site runs adjacent to a busy road (Reijnen et al., 1995). Research has therefore suggested that established woodland sites, free of major disturbance and possessing greater structural diversity than succeeding woodlands or coppiced woodlands, will provide for a greater array of bird species (Gil-Tena et al., 2007; Hinsley et al., 2009), though even amongst structurally similar habitats the species composition of a site may have a marked impact upon bird species diversity (Arnold, 1988).
In fact, a greater mix of tree species may bolster bird diversity, as was demonstrated by Díaz (2006) when bird species in pinewoods and oakwoods were found to be lower than in a stand containing both species. By a similar token, species composition may impact upon bird species that forage amongst foliage for arthropods and other food sources. Investigations by Robinson & Holmes (1984), for instance, demonstrated that the distribution of foliage within the crown of a tree will impact upon the foraging ability of particular birds; as will, but only at times, the size (and other characteristics) of foliage. Similarly, as particular tree species will attract certain arthropods, the species composition of a stand will impact upon the constituent bird species and their abundance. Thus, a mosaic of habitats that is mainly – but not at all exclusively – mature and mixed woodland may be most preferable if seeking to attract many species of bird. Such woodland need not be extensive in canopy cover however, as wood pastures attract such an abundance of insects that insectivorous birds can be found in great abundance, assuming the land is not treated with pesticides (Ceia & Ramos, 2016).
Building upon the concept of stand structure, the presence of standing deadwood is also important for birds. Whilst cycles of management are beneficial for some species, those that rely on old-growth stands with minimal management intervention are heavily reliant upon standing deadwood as a source of habitat (Drapeau et al., 2009). Those species which nest within recently-dead snags (or dead portions of living trees), including the woodpecker (Smith, 2007) – though also many species of secondary (successional) cavity-nesting species – will far more readily be found in stands of significant age that contain tracts of large (over 30cm DBH) potential habitat (Bednarz et al., 2004; Remm et al., 2006). Granted, not all standing deadwood is equal. For example, in the forests of British Columbia, USA, woodpeckers will preferentially frequent trembling aspen (Populus tremuloides), to the point that 95% of all cavity nests are found within this species – even in spite of its limited abundance within forest stands (Martin et al., 2004). Similarly, forest edge standing deadwood may be more preferable for some cavity-nesting birds (Remm et al., 2006), and at times standing deadwood created through recent forest fires may be most suitable (Nappi & Drapeau, 2011; Saab et al., 2004). Therefore, post-fire salvage logging may be detrimental to cavity-nesting birds (Hutto & Gallo, 2006). It should however be noted that not all cavity-nesting birds will create their own cavities from sites of decaying wood, and may instead use natural cavities that have formed at the branch junctions of snags (Remm et al., 2006).
A parakeet making this cavity within a large branch of London plane its nesting site. Source: Authoor, 2017.
The benefits of standing deadwood extend beyond the mere provisioning of viable nesting sites, however. They also act as suitable feeding platforms for many bird species, again including the woodpecker. In particular, decaying snags with lower wood densities will provide the suitable conditions for foraging (Farris et al., 2004; Weikel & Hayes, 1999). This is because such decaying snags attract saproxylic insects, which are viable sources of food for birds (Drapeau et al., 2009). However, this does not necessarily mean that such snags should be extensively degraded, as research has also suggested that snags with only some deterioration (through fungal decay and fire damage) are optimal for foraging (Nappi et al., 2003; Nappi et al., 2010). Without question, larger snags will normally provide for greater foraging potential, and not only because of the greater diversity of foraging site types (small branches, large branches, and the stem), but also because of the greater surface area upon which birds (including woodpeckers) may forage (Smith, 2007). By a similar token, snags can also be used for perching and communicating (Lohr et al., 2002), which could be of advantage to predatory birds and breeding birds, respectively.
Coarse woody debris (fallen deadwood) upon the woodland floor can also be of use to bird species. Lohr et al. (2002) identify such downed woody debris as being important for foraging, perching, and communicating; albeit at a generally lesser rate than standing deadwood (snags), though not always (Spetich et al., 1999). Understorey bird species may also utilise downed stems for nesting. Where coarse woody debris is removed therefore, bird species diversity and population abundance will almost certainly suffer (Riffell et al., 2011).
A bird that has used these Ganoderma brackets, which themselves reside between two buttress root of horse chestnut, as a nesting site. Source: Author, 2016.
Of course, it is not only standing (snags) and fallen deadwood (coarse woody debris) that are of benefit, but also the decaying wood of living trees. Typically, it will be trees with more extensive internal decay and thus thinner strips of functional sapwood that will be more preferable to cavity-nesting birds (Losin et al., 2006). However, it is the larger individuals within a stand that will again be more readily frequented, with research by Conner et al. (1994) finding that the red-cockaded woodpecker (Leuconotopicus borealis) requires decaying heartwood of 15cm in diameter (or greater) to form a viable nesting site. Such extensive and suitable heartwood can usually only be found in older trees (Hooper et al., 1991), which therefore outlines the importance of conserving old-growth stands and retaining mature individuals during harvesting operations. In fact, red-cockaded woodpeckers will seek-out older trees wherever possible, because of the greater heartwood extent found within such trees (Rudolph & Conner, 1991).
Furthermore, akin to standing deadwood, not all trees are equal in their provisioning of viable habitat for cavity-nesting birds. Certain bird species may favour particular trees that are being decayed by specific heart-rotting fungi. Using the red-cockaded woodpecker as an example again, it is understood that Pinus spp. being decayed by the heart rot fungus Porodaedalea pini (syn: Phellinus pini) are highly desirable sites for nesting for the species (Jackson & Jackson, 2004). Similarly, the great spotted woodpecker (Dendrocopos major) will commonly frequent large oaks complete with large tracts of decaying heartwood and fungal sporophores (Pasinelli, 2007).
Birds may also utilise the tree’s flower (florivore), fruit (frugivore), and seed crops (granivore), as a source of food. In fact, birds are considered the most significant dispersal agent of a tree’s fruit and seed crops, which is testament to the important relationship birds and trees have in this regard (Howe & Primack, 1975; Sedgley & Griffin, 1989). Certain birds are even associated largely with specific tree species, such as how the Eurasian jay’s (Garrulus glandarius) main food source is the acorn of the oak (Quercus spp.) (Vera, 2000). Open-grown mature trees may typically harbour the greatest crops (Green, 2007), and parklands, pastures (Galindo-González et al., 2000), savannas (Dean et al., 1999), and even gardens and orchards (Genghini et al., 2006; Herzog et al., 2005) may be home to many such trees.
A jay proudly carrying an acorn. Source: Phil Winter.
Unfortunately, pressure on these environments, be it in the form of grazing, chemical applications (particularly in orchards), or simply human activities, has led to declines in constituent bird populations, in some instances (Bishop et al., 2000; Elliott et al., 1994; Thiollay, 2006), though historically orchards amongst extensively-grazed wood pasture were highly valuable for bird species, which would feed upon the abundance of insects (Barnes & Williamson, 2011; Oppermann, 2014). Beyond the open-grown tree however, copses, woodlands, and great vast forests all have the ability to harbour birds, courtesy of their crops. Secondary and regenerating stands may perhaps provide for the greatest abundance and diversity of food for birds, given that the greater light levels provide suitable conditions for a wider range of plant and tree species that flower and subsequently produce fruits (Martin, 1985).
Additionally, the better light conditions mean such fruiting species are likely to be healthier and produce bigger and more plentiful fruits, which is of importance to foraging birds that seek out proteins, fats and carbohydrates from tree crops (Sedgley & Griffin, 1989) and insects attracted to flowers. One example of this would be how the plentiful silver birch (Betula pendula) stands, in Belfairs Wood (Essex, UK) during the 1970s, over-masted quite significantly and consequently attracted very large numbers of redpoll and finch (Carduelis spp.), which all foraged eagerly for the seed. By-and-large, as birds will seek-out fruits and seeds that are larger than average and in healthy supply upon a tree (Foster, 1990; Wheelwright, 1993), it is perhaps not surprising that such regenerating stands are highly desirable. Granted, closed-canopy and late-successional stands also harbour tree crops (including the acorns of Quercus spp. and keys of Fraxinus spp.) that are of huge value to birds (Greig-Smith & Wilson, 1985; Koenig & Heck, 1988). However, the poor soils (nutritionally and hydrologically) of many mature woodlands adjacent to agricultural landscapes had led to – at least in Australia – declines in fruit and seed crops and, as a result, bird population density (Watson, 2011).
Moving away from the woodland and forest stands, though not entirely returning to open-grown trees, we can observe how trees within field hedgerows can be of huge benefit to birds, as can trees within agricultural windbreaks. Benefit may come in the form of landscape connectivity, where hedgerows and windbreaks act as corridors connecting woodland patches to one-another (Davies & Pullin, 2007; Harvey, 2000; Leon & Harvey, 2006; Morelli, 2013), though they may also be used – albeit perhaps less frequently now, courtesy of increased hedgerow management (at least, in the UK) – as nesting sites and foraging sites (Benton et al., 2003; Netwon, 2004). Grass buffers either side of the hedgerow may aid with suitability for birds, as may the presence of a greater number of large trees within a hedgerow (Hinsley & Bellamy, 2000; Herzog et al., 2005).
Within urban environments, the presence of trees and hedgerows adjacent to busy roads can however have a negative impact upon birds, by increasing mortality rates (usually associated with birds flying out into oncoming traffic). Research by Orłowski (2008) concludes as such. Of course, the presence of trees is also of benefit, much like within farmland hedgerows. Urban street trees, and also those within gardens, can improve landscape connectivity, allowing for bird species to travel between more significant areas of tree cover found in parklands and urban woodlands (Sanesi et al., 2009). In particular, connectivity to older parks with remnant woodland fragments will support a greater diversity of bird species (Fernández‐Juricic, 2000). The advent of large coniferous tree (and hedge) planting in many urban areas, courtesy of the planting of the cypress and other conifers (including Chamaecyparia lawsoniana, Cupressus macrocarpa, and x Cupressocyparis leylandii), has also led to an increase in resident bird populations and primarily because of the over-winter shelter such coniferous tree species provide (Jokimäki & Suhonen, 1998; Melles et al., 2003; Rutz, 2008; Savard et al., 2000). Furthermore, sheltered trees within the urban landscape that have abundant fruit and seed crops can be of huge benefit to birds, by providing essential food sources in an otherwise somewhat undesirable landscape. For such reasons, urban parks and woodlands may potentially provide the best conditions for certain feeding birds, though large gardens complete with dense vegetation may also be of great importance. Tree-lined streets may also be critical, and notably so if trees are large, have dense crowns, and have an edible fruit or seed crop.
Large leyland cypress specimens inter-planted with poplar cultivars offer suitable nesting sites in this harsh industrial zone. Source: Author, 2016.
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“The tree is damaging my brick wall!“, they exclaim. “Fell the tree!“, they demand. Frankly, the word “no” would be sufficient, in at least a good portion of cases. After all, there’s an easy engineering solution that not only balances the need for a crack-free wall and the presence of a tree, but also signals ingenuity and a reasoned approach to situation management – the bridging of said wall around the butt of the tree and its immediatly-adjacent root plate. The issue is addressed in various publications, including Tree Roots in the Built Environment, and it is a message that needs to be communicated to homeowners and tree owners alike. More of the below, please!
A fairly large sycamore (Acer pseudoplatanus) within touching distance of a low brick wall and a pathway. A recipe for disaster, surely? No! The tree can easily be retained via a simple feat of engineering, as we can see even from afar.Not only does the remaining wall have a much lower chance of being directly damaged by the secondary thickening of the sycamore roots, but it also saves on bricks!We can see how the roots sit snugly beneath the brick wall, and the tree is making itself even more cosy by girdling itself………… (?).
It’s fair to say that the epithet fraxinea is not indicative of the quite broad host range of this fungus. Granted, the same can be said about many other fungi, including Rigidoporus ulmarius and Pleurotus dryinus, and perhaps that’s one of the things we have to watch out for when it comes to identfying fungi on trees (and more broadly). Dealing specifically with Perenniporia fraxinea, which probably doesn’t have a common name, I want to share what other hosts I have come across that display signs of colonisation by this fungus (specifically, by identifying the fruiting bodies on the trunk and buttress area). This is, after all, an important aspect of tree management, and pin-pointing where fungi may occur outside of their suggestive range (by virtue of their epithet) is critical as a consequence. The mycological world loves to throw us curve-balls, and therefore we must be able to catch them when they are indeed thrown.
For the sake of ease, I have segmented the below pictures into headings detailing the different host species of Perenniporia fraxinea. I hope that some readers, either now or those who find this via a search engine in the future, find this of use – particularly those in the UK. However, before that, I shall list the host genera Ryvarden & Gilbertson list in their publication European Polypores (note this applies to all across Europe): Aesculus, Castanea, Celtis, Eucalyptus, Fagus, Fraxinus, Gymnocladus, Juglans, Olea, Malus, Platanus, Populus, Prunus, Robinia, Quercus, Salix, and Ulmus.
Acer pseudoplatanus (sycamore)
Only once have I come across Perenniporia fraxinea on sycamore and that was down in Dorchester, UK.This sporophore as a bit of a mess, with regards to its morphology. Nonetheless, it had a hymenium, and was thus not an anamorph.Thankfully, the other side of the same sycamore sported a more typical bracket-shaped specimen. Note the white spore around the bracket.And a cross-section showing the distinctive context of Perenniporia fraxinea, including the fresh yellowish growth.
Aesculus hippocastanum (horse chestnut)
Again, only once have I observed this association. In this case, the horse chestnut was a monolithed specimen, and the sporophores were on the inside of the tree.Trying to hide in frass and white-rotted woody material!A cross-section, once again, reveals this fungus as Perenniporia fraxinea.
Fagus sylvatica (beech)
Three times have I witnessed this association on beech, and this was the most recent and the finest example of the bunch. Some great buttressing, too – as is so frequent on mature beech, which look like they’re essentially being ripped out of the ground in which they sit.A closer look at this tiered specimen, complete with white spore dressing the buttress root. Upon cutting this one for a cross-section, it exuded a nasty ‘juice’.Note the context, which is very distinctive of a specimen that has had its most recently growth ‘spurt’ mature – i.e. it lacks the yellow-orange rim.
Populus spp. (poplar)
Both Populus x canadensis and Populus nigra ‘Italica’ are hosts I have seen Perenniporia fraxinea on within the genus Populus. Here, I share the better example of the two from the Lombardy poplar. A cracking buttress root there!On one side of the base we see this collection, all of which are laying down some very fresh growth.And on the other side some equally fresh growth spurts are taking place. Very photogenic!
Quercus robur (English oak)
Having shared some other examples of Perenniporia fraxinea on oak, I wanted to share a newer example from last week. Three times I have seen this fungus on oak.Here we can see it’s certainly a sporophore with many years’ growth. This time around, a small layer underneath has been added.The white spore is so distinctive here, and the upper surface is covered in algae, etc.And a shot of the hymenium for good measure.
Robinia pseudoacacia (false acacia / black locust)
Robinia pseudoacacia is the second most common host after ash, in my experience (seen it a total of five times on this species). This is an example from earlier today.Here we have a sporophore right at the base.And some further up – albeit, much smaller, in this instance.A closer inspection of two very good-looking sporophores.And a closer shot of the one at the base – including the white spore once more.And finally the context, as is typical of this fungus.
It has been rather quiet on the blog front this past week, because I have been spending much of my time out-and-about. I was down in the New Forest this Sunday just gone, at Hatfield Forest the weekend before, and have also attended a conference or two – all in addition to my day job! Thus, much of my spare time has been spent deep in books, and notably fungi ones. After all, it’s the season to see them at their best, with many fungal species kicking into life, and because many associate with trees it’s important to know what you’re looking at – at least, to the genus level.
I could spend forever-and-a-day posting what I have found over the past few weeks, and thus to whittle it down to just a few to share here is darned difficult. Thus, the ones below are the more interesting ones that may not be seen every day, or fungi that are common but in this instance adopting an interesting form or state of decay.
Aurantiporus fissilis (greasy bracket)
A fallen mature ash (Fraxinus excelsior) sports a large whitish fruiting body of the rather infrequent – but seemingly widespread – fungus Aurantiporus fissilis.A side profile reveals a slightly waved morphology. Pretty cool!What a great shot this is. Growing right out from the centre!
Baeospora myosura (conifer cone cap)
This fungus is different. It is growing upon shed cones of a nearby conifer. In this case, it;d either be from a pine or Douglas fir. It appears to be the latter, though I didn’t look well enough when this fungus was found.
Bulgaria inquinans (black bulgar fungus)
A fallen oak, which may have only fallen earlier on in the season, as leaves are still attached to the branches. Notice the large black spots all along the trunk and branches.Along one of the lower branches, we can observe a myriad of different-aged fruiting bodies of the Ascomycete known scientifically as Bulgaria inquinans. It is suspected to be an endophyte that strikes quickly after the host dies (or a branch dies). In this case, it got the entire oak!The younger fruiting bodies have an outer brown rim and soon ‘roll-out’ to form black discs (as seen to the top right).I threw this is as it is a lovely photo.
Chlorociboria aeruginascens (green elf cup)
It’s this little dude again. I just had to share this one, as it’s such an awesome Ascomycete. Also note some sulfer tuft (Hypholoma fasciculare) to the right of this log.A closer inspection, so one can admire.
Clitocybe nebularis (clouded agaric)
Here the fungus Clitocybe nebularis forms a complete ring (fairy ring). It is hard to see, because of the brambles, but it’s a full ring and is very beautiful.Here are a few of the mushrooms, which soon track underneath the scrub.
Fomitopsis pinicola (red-banded polypore)
A dead birch plays host to some conks of the nationally rare fungus Fomitopsis pinicola.Just below the failure point, sits this guy. A nice and lofty position from which to sporulate, no doubt.Slightly further down is another one, and from this example we can see why it is called the red-banded polypore.On the floor, the other part of the trunk is entirely adorned with the conks, too!Here are three younger ones, which lacks the mature banded appearance.This one even lacks the red band – it’s more of a brown-banded polypore! The best way to distinguish this one from other conks from the tinder bracket (Fomes fomentarius) and Ganoderma species is to take a cutting, if the red band is lacking.Some conks collected for preservation.The context differs from Fomes fomentarius and Ganoderma spp. in the sense that it is much lighter in colour – almost white, sometimes.
Mycena epipterygia (yellowleg bonnet)
This oak log is carpeted with moss, though also has some little Mycenas popping through.These ones have a yellow stipe, and are probably (though the identification is not certain, as there are a few with yellow stipes) Mycena epipterygia.This shot is now my desktop background. Such a delightful little group!
A long-fallen beech (Fagus sylvatica) is often host to many fungi. In this case, we have a later-stage entrant to the scene: Phlebia tremellosa.This cluster of fruiting bodies sit proudly adjacent to a single conk of Ganoderma australe. Both induce a white rot, and thus the wood of this beech is both very wet and very soft.Atop the trunk, these three specimens have a maturer colouration towards their centres.The ones on the side of the trunk are not as mature, though are certainly adorable. Quite fluffy atop (though still very jelly-like), if you get the chance to look at these under a hand sens then please do – they’re so cool!
Pholiota aurivella (golden scalycap)
I saw a lot of fresh ones in the New Forest and they were sublime (they really are golden), though the ones at the base of this topped ash (Fraxinus excelsior) are more worthy of a place here. You’ll see why.They’re over-mature, and have begun to really decay.They still retain their lovely cap texture, however.Breaking the cap off reveals the gills below and the very decayed interior, which is being consumed by insect larvae.I ruined this guy’s home, unfortunately. I put the cap back afterwards, so hopefully the conditions persist to allow these guys to develop. This set of shots therefore shows the importance of decaying fungal fruiting bodies for insects and other fungi and bacteria. A whole mini ecosystem!
Sparassis crispa (cauliflower fungus)
Found just this afternoon in a churchyard, this douglas fir (Pseudotsuga menziesii) is supporting a mycelial colonoy of Sparassis crispa.Huzzah! Anyone for dinner? They even sit on a lovely bed of needles and cones.These are less than a week old, as they were not there this time last week. They are both around 10-15cm across.Another close look but peering down slightly.And what a view of the church they get during their ephemeral existence.
Arboriculture 