“From acorn to ancient” – contrasting open-grown and forest trees

In spite of Ted Green remarking that he is “stating the obvious” in this chapter of his, it’s nonetheless good to be reminded of the benefits of open-grown trees and how they compare to closed-canopy trees of a similar age. Despite certain similarities, there really are many differences in today’s age, and we’ll explore some of them here. Before that however, it is interesting to note that the utilisation of open-grown trees during ‘ancient’ times was not uncommon. Orchard trees, for example, demonstrate man’s understanding of open-grown trees producing a much greater abundance of fruit than closed canopy trees.

Open-grown individuals

Morphologically, a tree that has grown without any marked competition will be vastly different to a tree that has grown amongst its competitive peers. Due to a reduced competition for light, and also because of the greater effect of wind upon its structure, an open-grown tree will be shorter, have a fatter trunk, a wider crown (perhaps with vastly-spreading and near-horizontal limbs), and a more significant anchorage root system. This ensures it is well adjuested to its setting (principally in allowing for optimal photosynthesis whilst retaining structural stability). Amazingly, investigations into the rooting systems of open-grown veteran trees by the Ancient Tree Forum revealed roots with a 2.5cm diameter at a distance of 50m from the base of the tree.

A mature open-grown oak pollard, complete with an absurdly broad crown with many near-horizontal limbs. Certainly an effective means of balancing photosynthetic needs with stability!

On a biodiversity level, we must also recognise that roots are host to a massive array of mycorrhizal associations. If an open-grown tree has a huge rooting system, associations with the tree (directly) will be potentially vast, though perhaps isolated somewhat (assuming no other trees are about). Shed roots may also support organisms of the decmposition subsystem (fungi, in particular).

Looking at the above-ground structure of an open-grown tree, we can also observe associations with a great number of species. For instance, the large limbs and vast canopy area of an open-grown tree will provide habitat for many insect species, and entire trophic systems surrounding their presence (from parasitic wasps to mites, and from birds to fungi and bacteria). Similarly, the very large and broad main stem will have a vast quantity of substrate (wood, cavities, hollows, and so on) available for saproxylic species and nesting birds, which will typically revel in the warmer conditions. The herbaceous plant species surrounding the tree will also provide support for insects, including saproxylic beetles.

Closed-canopy individuals

Because trees growing within a woodland or forest have to compete for all types of resource (light, water, nutrients, rooting space, branching space), their form will be vastly divorced from the open-grown tree. Investing most of its resources into growing towards the light, stems will be thin, lack taper, and rooting systems will be largely insufficient to support the tree structurally (which is evident when woodland edge trees fall following localised tree felling). However, root grafts (between a single species) and mycorrhizal relationships between individuals (across different species) may ensure that edge trees, which have larger canopies, support trees (via grafted roots and mycorrhizae) in more sheltered but still very local settings. By that same token, older trees may support younger individuals (particularly of the same species).

In time, deadwood within woodland stands may build up to significant quantities. As a stand ages, there is a progressive ‘self-thinning’ of the stand, eventually leading to only some (usually mature and quite large) trees remaining. This accumulation of deadwood ensures that the decomposition subsystem can mineralise nutrients, allowing these remaining trees to utilise these resources once again. The same can also be said for leaf litter, which is of far greater quantity within a closed stand (and retained, courtesy of a more sheltered micro-climate). For these reasons, and compiled both with the fact trees will ‘trade’ resources in a sort of peer-to-peer economy and their sheltered setting, rooting systems may be less expansive (compared to open-grown trees). Buttressing may also be lacking, unlike in open-grown individuals.

A stand of beech (Fagus sylvatica) last pollarded before 1830. We can see how the crowns of each individual are much more upright and narrow, and the stems have less taper than they would in an open setting. There is however a great abundance of leaf litter on the floor, though an unfortunate lack of coarse woody debris (excluding standing deadwood).

The decomposition associated with woodland stands will also be far quicker, given the cooler and moister conditions. As fungi tend to operate most effectively in such settings, the mineralisation of locked-away nutrients will be a much swifter process, when compared to the decomposition of deadwood on and around an open-grown tree. For instance, a large stem of a fallen tree within a woodland may decay in a few deacdes, whilst a fallen and significantly-sized limb of an open grown tree may take up to a century to fully decay.

Clearly it’s not possible to compare and contrast trees in different setting in any short space of time, though I felt that this brief entry by Ted Green in the below book was a rewarding read, if not to simply cement existing knowledge.

Source: Green, T. (2007) Stating the obvious: the biodiversity of an open-grown tree – from acorn to ancient. In Rotherham, I. (ed.) The History, Ecology, and Archaeology of Medieval Parks and Parklands. UK: Wildtrack Publishing.

If you wish to talk about this post, please do so here or via Arbtalk.

Co-dominant fork (with bark inclusion) failure on beech

An old pollard that had three stems before it had but two (though it now has only one!), we can see how recent the second failure event was. We had some strong winds last week, and I suspect this occurred then. Massive failure, though given it’s within Epping Forest it’ll be left on the deck and be host to many species of fungi and insect in the future.

Looking at the failure zone, an area of bark inclusion was evident. No doubt, this impacted upon the structural integrity of the beech, and facilitated with its failure a week or two ago.

A nice surprise on the opposite side of the tree, as well. And no, it wasn’t a winning lottery ticket.

Quite a nasty failure!

But we can see how the area of bark inclusion didn’t help. There’s also some decay in there.

And where another stem tore out (many moons ago), Ganoderma sp. (suspected Ganoderma applanatum) have colonised. Massive brackets!

Trametes hirsuta on a fallen beech (Fagus sylvatica)

You’d be mistaken for thinking Epping Forest is comprised of a pure beech monoculture, though it’s simply a case of most of the interesting fungi being found on the very old beech pollards on the site. Hand on heart, there’s at least one hornbeam, three oaks, and three wild service trees in the forest!

This fungus I had initially thought was Pseudotramates gibbosa (‘the stumpgrinder’), though Ted Green remarked that it was in fact Trametes hirsuta (syn. Coriolus hirsutus). This is because the latter has small and circular pores, in place of a more maze-like underside. Ted Green went on to comment that this fungus is not overly common in the UK, as it thrives in the warm and dry climates of mainland Europe more so than it does here. However, in recent years it has been found in the South East, and it may work its way northwards in time.

In this case, its colonisation on the upper surface of this downed beech stem is telling, as this region of the wood substrate is going to be drier and more exposed (and thus warmer). Such conditions are far more suitable than what is found on the underside.

A very neat arrangement of sporophores, in absolute abundance.

Atop, it appears to be very similar to Pseudotrametes gibbosa.

But beneath, the pore structure is different. Not a good photo, and in hindsight I’d have got a better one, but alas!

A rather massive Ganoderma sp. upon a dead strip of a beech stem

Again, this was found at Epping Forest during yesterday’s visit with the Ancient Tree Forum. This time, we can see a very hefty Ganoderma sp. (suspected Ganoderma applanatum), found fruiting upon a long and very extensive dead column of a beech (Fagus sylvatica) stem. The actual tree is still alive, though the crown is rather small in comparison to the entire structure.

Here we can observe the sporophore emanating from a dead section of its host. A slight upward orientation of the sporophore can be seen. Has its host shifted slightly in orientation, due to the decay?

From this angle, the growth increments can really be identified. A beatiful sporophore!

And we can see howe bleedin’ massive it is! Also note the small sporophore on the same side but right at the base, and a slightly larger one on the floor beneath. On the right hand side of the small basal hollow, we can also see the remnants of an old sporophore (again Ganoderma sp.).

Here is the beech as a whole. It evidently has only half a crown.

Perenniporia fraxinea on beech (Fagus sylvatica)

Along one of the paths in Epping Forest sat a large and very mature Fagus sylvatica, and at its base was a good-sized Perenniporia fraxinea sporophore. Around the region colonised we can identify some serious buttressing. This may likely be due to the fact that the penetrable soil depth is no greater than 60cm in places, though the presence of this white-rotting fungus may also very likely be inducing some reaction growth. It’s the first time I have come across this fungus on beech, so I thought I’d share the below photos.

Here sits the sporophore, between two root buttresses.

A side profile shot reveals its prominence.

Panning back, we can see exactly how significant the buttressing is in this region. Evidently, it is more extensive than in the regions away from the area where the sporophore is emanating from.

A glorious oak pollard with an added extra

Again one from today (Ancient Tree Forum meet at The Warren, Epping Forest), though this time the ‘main’ focus is the tree. In the below image, we can see a very large oak that has been historically pollarded, though such management has since lapsed (the last time it was pollarded was prior to 1830). We can see at least five stems that remain, with a sixth being lost some years ago (as shown by the large tear-out). On this tear-out, we can also see what appears to be the remnants of a Laetiporus sulphureus (the white mass). I couldn’t get close enough to give a definitive identification, though I strongly suspect it is indeed this fungus (which we know may often fruit upon a wound surface).

A very hefty oak pollard, complete with at least one tear-out.

In that tear-out, we have what looks like the remains of a Laetiporus sulphureus sporophore. If it is then that’s hardly surprising, as I have seen this fungus produce a sporophore on an open wound in many an instance.

Daedaleopsis confragosa on a fallen birch log

At an Ancient Tree Forum event today, which was hosted at Epping Forest, I came across a huge array of fungal species on multiple host species. I’ll be sharing many of these photos over the coming week, as well as some awesome pictures of old coppiced and pollarded beech and hornbeam. However, for now, I’m sharing a few shots of some blushing brackets (Daedaleopsis confragosa) on a small piece of coarse woody debris from Betula pendula. These are nothing particularly rare, and I have also seen them on fallen birch logs before, though it’s a good example of the fungus and builds on my recent post showing it on willow.

We can see four sporophores on this small log.

A closer inspection of the one on the bottom right. It has largely remain unblemished.

More of a side profile on this one. A very thin sporophore, in this instance.

Daedaleopsis confragosa on willow (Salix sp.)

During the autumn months of last year, I came across this decent-sized sporophore of the blushing bracket (Daedaleopsis confragosa). From memory, this was a crack willow (Salix fragilis), though I honestly cannot remember. Regardless, it’s a very good example of what this fungus can achieve without being ‘bruised’ (where the bracket turns red on the upper surface). The heartwood of this host will be subject to a white rot. As a willow species, such degradation is not particularly favourable, as the wood is generally rather weak.

Upon the main stem, from afar.

Coming in for a closer look, the bracket’s subtle morphology begins to become more evident.

As always, a lovely pattern atop. We can see this is, at least in part, two-tiered.

A look at the underside of the bracket.

Wind + bark inclusion + rot = impending cupboard door failure

It was incredibly windy over the weekend and into Monday, and at some point over that period of time this poor (and rather old) hawthorn failed quite majorly. On the windward side, an area of bark inclusion lead to a large crack propagating down the main stem. This crack allowed the tree to fold open in the wind, much like how a cupboard opens (hence the term ‘cupboard door failure’). I managed to capture this on video, which can be seen here (short version, complete with me talking) and here (longer and different version, without me talking). Please let me know if the video links don’t work, and I’ll re-upload them (at any time).

The hawthorn was felled that afternoon (given the risk of members of the public), and inspecting the hawthorn today revealed a very extensive decay column (a white rot fungus, which I suspect is Ganoderma australe) throughout the stem and up into the principal branching structure. In terms of t/R however, it was perhaps (at a glance) ‘sound’ enough to remain standing when looking at the lower trunk (if it hadn’t failed so gloriously, further up!). I have included some photos below of the aftermath.

Here’s the base of the tree, complete with a Ganoderma sp. sporophore (on the right hand side of the butt).

The cracks associated with yesterday’s video has stretched throughout this entire cross-section – almost.

Further up the stem, we can see how much the structure had folded out.

Opening up a cross-section of the stem, we can see very extensive rot.

There also appears to have been some wood-boring insects present, in the past.

Up in the lower crown, we can see how a heavily-decayed centre is surrounded on one side by extensive discolouration and developing decay.

Suffering street trees – the battle of the urban environment

Too many times do we come across trees that have simply been hacked at, battered and bruised at the base, or just appear outright stressed. It’s certainly an unfortunate sight, and it really does have an adverse impact upon the streetscape – unhealthy and unsightly trees can make an area appear uncared for.

In this case, we can see four Prunus cerasifera ‘Pissardii’ that, whilst relatively pretty in blossom, have suffered significant pruning wounds and basal damage (from the overhead wires being kept free of branches and parked cars, respectively). As a result, fungal colonisation has occurred, and their form is not to be desired. Even during summer, they aren’t particularly graceful specimens. I sounded all four with a hammer, and they didn’t indicate extensive hollowing, though I remain sceptical about there not being much decay. Given sporophores have breached out onto multiple sides of all of the trees, their decay columns may very likely be extensive (at least) in the radial direction.

Here sit the four trees, within small planters in the pavement. Atop the crowns, we can see electricity and phone wires.

This individual bears the marks of previous topping cuts. At the base, we can see a Ganoderma sp. (suspected G. australe).

Another individual shows fewer signs of aggressive past pruning, though upon close inspection it has lost quite a few large branches in the past (as a result of keeping the crown clear from the overhead wires and the roadway).

A third tree. Again very messy, and again not particularly graceful. There is plenty of fungal colonisation at the base of this one.

Here we can see the overhead wires and how the crown has been historically pruned back.

A close up of a Ganoderma sp. (suspected G. australe), which are found on three of the four trees.

A second tree shows signs of colonisation on both sides of the butt (old brackets), with a central sporophore still active.

A large branch removal has allowed Laetiporus sulphureus to colonise. Here, we can observe an old sporophore. It will likely fruit again this year.