Trees Over Time 08: Anomalies

Fact is stranger than fiction. Take, for example, the sea cucumber that breathes through its bottom and, when attacked by a predator, fires parts of it innards at its enemy, growing them back later when it has done an inventory as to what is missing. I’m afraid the average human’s imagination is just not capable of coming up with such implausible creatures; even our depictions of alien species tend to be derivative of animals we are already familiar with, such that we give our imagined aliens tentacles, horns, large eyes – and, of course, most of them speak English (especially in early editions of the Star Trek series). This observable limitation to our minds ties in with what is known as the ‘brain paradox’ – if our brains were simple enough for us to understand how they worked, then we would end up being too simple to understand our brains. To overcome this paradox, neurologists turn to technology but when AI starts understanding how our brains work, I think we need to watch out!

Like most complex life forms, trees do sophisticated things that we do not yet fully understand – and odd things that seem to be self-defeating or just plain weird. These complications increase further due to the many unseen interactions between trees, microbes, and aspects of a tree’s growing environment which we ourselves cannot see nor sense. The common question asked is “What has caused the tree to do this?” – and frequently the correct answer is “We just don’t know.”

In this Trees-Over-Time (TOT) article, I’ve put together some anomalies that didn’t readily fit within any of the other themes of my previous TOT articles: it’s a bunch of ‘leftovers’, is what I’m hinting at. We’ll look at a few physical anomalies, some theoretical anomalies and some tree management anomalies – and I’ll let the pictures and captions do most of the talking.

Another reason to look at anomalies is that they are away from what is standard, normal, and expected. This means there are often things to be learnt from them. If we just keep thinking in standardised, normalised ways, with fixed expectations, not only can life be dull, but it also greatly limits how we might conceive of trees and their management.

Finally, to get you in the right frame of mind for this article, here is a short mental exercise you can try. Imagine what it might be like being a tree: we know that trees can sense things and that they can respond to the stimuli they can sense, but they cannot think: so ‘thinking like a tree’ is the wrong approach. To get closer to a tree’s perceptions, try this example: a light breeze blows across the skin on your arm and that causes your arm’s hairs to raise up. You must only feel the sensation – not verbalise it, nor conceive of it, not reflect upon it nor theorise about it. So, no thoughts – just the sensation. Then you must take the next conceptual step: it’s the skin that’s directly experiencing the sensation, you need to ignore the transmitted messages that are arriving at your brain and imagine being those skin cells on your arm that are feeling the breeze, embedded as they are in a matrix of adjacent living cells with which they communicate. Oh – and you can’t visualise anything either, as trees can’t see. It’s tricky – but this exercise can get you nearer to understanding just how weird a tree is as a living entity if you can achieve this mental feat.

Physical anomalies

Odd extrusions and growths on the outside of trees are common anomalies (e.g. burrs, crown galls, sphaeroblasts and other (less explainable) polyps). When I have tried to time-lapse a few of these (Fig.s 2-5), though, it seems they mostly develop in size early in the life of that tree and there’s only limited growth later in their lifecycle. They may be a wood-turner’s dream – but I want to capture more of them at a younger stage to make an interesting time-lapse or two.

Figure 2: “Everyone gets their time in the sun” This seems the case for many crown galls formed on trees, like this one formed on the stem of a silver birch (Betula pendula Roth). Many of these galls appear to have an initial rapid period of growth, then they ‘stagnate’, remaining a similar size for quite some time, and I’ve found many then start to break up, starting from some areas of bark death then subsequent internal decay. The gall pictured is no exception: it’s a little bigger in diameter and height on my revisit, but parts of it are already decaying and falling away. It has had its time in the sun.

Figure 3: “Sphere of influence” Minor development of a sphaeroblast on the stem of a wild cherry (Prunus avium L.) over thirteen years. A sphaeroblast is an oddly rounded woody growth that grows from a cluster of bud initials on the stems and branches of trees. It could perhaps be classed as a type of gall – however, it is uncertain whether microbes have to be involved in their production, as some could represent anomalous tree growth influenced by plant hormone levels, for instance, or arise due to previous injuries. Like the gall (Fig. 2), it’s common for dead areas to start to appear on sphaeroblasts as they age, which has even happened in the case of this small example. A recent class of our degree students were a bit bothered that Wikipedia (that well-known font of knowledge and disinformation) did not have an entry for sphaeroblasts, so we collectively created one. Perhaps more anomalous tree growth habits should also be catalogued there. If policed carefully by experts, Wikipedia pages can be useful signposts towards primary sources of knowledge – although we strongly advise against students citing it as an academic source. It’s the anomalous encyclopaedia of the modern age, that’s for sure.

Figure 4: “Love in my heart” – but quite clearly a knife in his/her pocket too! Vandalism to the stem of a Cotoneaster in a public park, time-lapsed over eleven years. It looks like that love has faded with time. Although it’s common to think of the outer bark of a tree as dead and inert material that is incapable of changing, that is not the case. I have time-lapsed a few of these carvings on trees – they all distort and fade with age – sometimes to the point of illegibility.

Figure 5: “Subtle changes” I’m a big fan of ‘subtle’ – and you’ll only enjoy this image if you are too. This veteran ash tree (Fraxinus excelsior L.) is probably over two hundred years old – and only a part-shell of the tree persists after decay and failure of much of its stem. You might think that there wouldn’t be much change to be seen in such a living shard whose annual growth increments must be sub-millimetre. But look closely: it’s a good game of ‘Spot the Difference’…

Anomalies of thought and belief

When managing trees, you can learn a lot by observation: one must be careful, though, as this can end up inducing the odd belief or two that is unfounded. Only recently did I come across an explanation for the death of tissues on the underside of branches in a couple of urban trees. Apparently it was due to ‘a sap flow shadow’ (a made-up term), even though all the symptoms pointed at previous fire damage, which is all too common where people set bonfires under the canopy of trees, a shed burns down or a stolen vehicle is burnt out. An example like this suggests that an on-going conversation with other arborists – and/or some formal education in arboriculture – might keep in check the development of some of these anomalous thoughts and beliefs.

Common attributes of the development of anomalous beliefs about trees are:

·      Only one factor is considered in what is a complex relationship (Fig. 6)

·      A technique is not fully understood and thus misapplied (Fig. 7)

·      A gut instinct is taken to be true, despite lack of empirical evidence (Fig. 8)

·      The mindset that trees grow to a fixed template – otherwise they are defective (Fig. 9)

Figure 6: “Strangle me and I’ll strangle you” Part of an ivy stem (Hedera helix L.) that has embedded into the stem of a hawthorn (Crataegus monogyna Jacq.). It is common to think of only one side of this relationship: that a climber wraps around the stem of a tree and that will throttle the stem. However, as the ivy stem starts to be occluded into the woody stem of the tree, it cannot increment in those parts compressed against the tree’s stem, and, sometimes, the climber’s stem will be throttled instead. Perhaps you have never thought of the process of secondary thickening as a weapon – but it is a key weapon in the armoury of trees that must defend themselves against all-comers.

Figure 7: “Mulching madness” How can such a simple thing as mulching go wrong? Easy – put humans in charge of the process! This odd configuration of mulching in a public park had me puzzled at the time. I’ve previously thought it was an attempt to create a new ‘bed’ in the park – but why not remove the grass under the one tree that has been planted? Perhaps the work specification stated “Mulch around the tree” – and that’s exactly what the contractors did – leaving that little island of grass right next to the young tree for some visual interest? On my return to this area, the mulching of this Cornus controversa Hemsl. ‘Variegata’ has become more rational.

Figure 8: “Lean isn’t mean” It seems that some people deliberately look for simple and easy ways to condemn a tree – to create an argument to get rid of it. That’s very sad. That leaning trees are at greater likelihood of failure than trees with a vertical stem is a frequently reoccurring argument used to justify tree removal. The reality is such a simple rule does not apply to the sophisticated woody constructs that trees produce: trees can make too many biomechanical adjustments for us to reliably second-guess them. Personally, I think we should see leaning trees as relatively friendly organisms: they are honest – in that they make clear where their fall zone is most likely to be; and they are generous – giving an arboriculturist repeated employment to monitor their lean.

Figure 9: “The oak with the hairy back” This is a pleasing time-lapse of a mature oak tree, released from a beech tree’s dominant canopy, presumably because the beech had some decay at its base, and the beech’s time for ‘playing in the park’ was deemed to be over. There will surely have been some increased likelihood of limb or stem failure for a one-sided tree like this, when experiencing greater wind exposure due to this neighbouring and dominant tree being felled. Through growth and adjustments, though, that likelihood tends to lessen with time. Great to see this oak taking advantage of the new space around it – although, note also how much the ivy has also developed in this ten-year time lapse. For this tree, I’d advise not allowing a large head of ivy to develop on it – for the tree’s sake more than anything else.

Surprise! Surprise!

The TOT process, of going back to trees after a decade – or maybe 13-14 years now, as time moves ceaselessly onwards – brings a roller-coaster of emotions – interest, excitement, disappointment (especially when a tree you are looking for has been removed) and surprise. My biggest surprise so far has been finding that two stems had fused together in a young horse chestnut, which appeared in the first TOT article but there have been quite a number of others. Here are just a couple where what one might expect to find or look for turns out differently.

Figure 10: “Much at stake” Initially I took this image because of the interesting spiral grain on the stem of this young whitebeam (Sorbus aria Crantz. ‘Lutescens’) in an urban car park. Revisiting the tree to see if the spiral grain had become less prominent, more prominent or about the same, it wasn’t that which ended up interesting me, so much as that the stake and tie were in exactly the same position that they were thirteen years before. I was so surprised at this complete lack of change I kept blinking and looking at the image again and again… It is wrong-headed to use tanalised stakes to support trees if you have no intention of re-using them after the tree has become established. Unfortunately, I have many images of such over-preserved stakes causing damage to trees – and even becoming occluded into the bases of young trees. In this case, this whitebeam has not grown quickly (it’s in a central reservation in a car park, so it’s probably struggling in a small soil volume), otherwise its stem would be in contact with the stake, causing it unnecessary harm.

Figure 11: “Blam!” I have a lot of photographs of tree forks – who doesn’t, right? This one is of a cracked fork in a large-growing willow (probably a cross with some Salix alba in it). When I plan a revisit, I think in advance about the likely outcomes and whether it’s worth going back to have a look. Clearly, the initial image showed a situation which was a win-win scenario to revisit, as either this cracked fork had failed in Storm Ciara – or it had persisted much as it was before. Wrong! An adjacent alder tree had failed at its roots and slammed itself right into the split fork. These sorts of examples are teaching me not to anticipate any changes to my TOT trees that much – but just to go and have a look without pre-judging what’s likely to have happened.

A tree walks into a bar…

It can be surprising how little the process of secondary thickening of trees is anticipated by site managers. A common result of forgetting the fact that tree trunks get fatter with time is they are often ‘swallowing up’ sundry static items such as fences, wire, posts, and the occasional bench. The meme in this collection of images of trees occluding foreign objects is the famous bicycle occluded into the fork of a pine tree – and, like many memes, it obscures the fact that such occlusions are very frequent and that one can learn more from looking at a range of examples, rather than repeatedly bringing up just the one (Fig.s 12 and 13).

Figure 12: “Full metal jacket” Metal tree guards are quite commonly occluded by trees in my experience. This is more than a little silly – as some of the guards are robust, expensive, and readily re-usable, so they should be moved on to help establish other new urban trees on a regular basis. For some, like this one around a maturing London plane (Platanus x acerifolia Willd.), it just becomes a feature of the tree. Two things can be gained from this image: i) the way the secondary thickening of the tree appears to be ‘flowing’ over the ironwork gives an interesting perception of the fluidity of secondary growth – something that otherwise we might think to be a process that pushes objects away from a tree; ii) that records should be kept of such occlusions, as this is really going to prove a problem when it comes time to fell this tree! Otherwise, considerable damage will occur to a Stihl MS 880!

Figure 13: “Sitting on the fence” Occlusions of foreign objects are really common in our urban trees: having visited all the main parks in the Greater Manchester region in 2018-2019, I came across many occlusions of iron railings, fencing, wire, posts, stones and other inanimate objects. Personally, I don’t class this as ‘damage’ – although the consequences can be dire for the tree in a few cases. This sycamore, occluding an old park railing, is a great teaching aid. Note how the adverse taper of the tree stem has increased with time. The occluded railing is lending substantial mechanical support to the tree, disincentivising secondary growth below the railing. Over time, this tree will become more and more reliant on this artificial support, which teaches a much broader point - that support systems need to allow for flexure and trees need to be feathered off from any support if structural independence is the aim.

Unlikely Comebacks

Too often, we can concentrate excessively on the drawbacks of urban trees: complaints from the public used to grind me down each summer when I worked as a tree officer, attending maybe thirty per day at times. Many of the complaints could be said to be more related to the benefits of trees, if you consider them from a different perspective:

·      “It’s blocking my view” = the tree is supplying valuable screening of your ugly house

·      “It’s making my garden shady” = it’s cooling down your open space and lessening the risk of you getting skin cancer

·      “It’s producing seedlings all over my garden” = it’s providing “trees for free”!

Working with coppiced hazel from a young age, I have always valued and admired the ability of many trees to regrow from a cut stump. Some arboricultural practices are a bit ‘binary’ – even though I know a lot of highly knowledgeable arborists/arboriculturists who are more than capable of thinking laterally. When a valuable tree in an open space or garden must be felled – there is a very strong tendency to “think binary” and purchase a new tree from a nursery to replace it. What if the stump produces some re-growth? That’s a tree for free – and it’s actually the same valuable tree that was felled – and it will also often establish at a much faster rate than any imported tree and it comes without the biosecurity risks - so why isn’t the protection and formative pruning of re-growths a more common practice in arboriculture?

Obviously, it’s very annoying when a tree that needed to be got rid of grows back – but, personally, I still admire that – I admire a tree that doesn’t die easily. Figures 14-17 show some examples of ‘comeback trees’ which I think can teach us something about sustainability in our urban forests.

Figure 14: “How many died?” This is, perhaps, a case of anomalous data reporting more than anything else. Although Dutch elm disease seems like it was something that happened in the 1970s, it is still a common issue for arboriculturists like me. This is because the local population of field elms (Ulmus minor Mill.) is on a cycle of regrowth, disease, dieback of their stems and then regrowth. Although a previous report stated that twenty million elms were ‘killed’ by Dutch elm disease in the UK (Gibbs et al., 1994), it really depends on what you think of as a tree and what it means to be ‘killed’ – as most of those 20 million elms are still growing in the UK. The cycle of “death” and regrowth is captured in this cluster of field elms by a lane in Garstang, Lancashire: such clusters of elms are a new meme of the English landscape, although the average layperson is blissfully unaware of that fact and thinks all the elms died out ages ago.

Figure 15: “I’ll be back!” Aside from elms, many other UK trees are capable of re-growing from their cut stumps. This is surely a boon that we can make use of in our urban forests. Pictured is a car park island, which was adorned by a common lime (Tilia x europaea L.) until the tree was felled. Limes are pretty reliable for re-growing back in this way – we even had one lime in one of my previous roles that grew back in a verge after two ‘doses’ of the stump grinder. Sometimes I think we have such fixed ideas about what a tree should be and what it should look like that we miss opportunities to make use of such re-growths. If you check my first ‘Trees over Time’ article, it’s possible to retrain regrowth from a stump like this into a good tree form again – yet this seems to be a rare occurrence in arboricultural practice. Again, this is possibly a consequence of the chainsaw being the “tool of choice” in arboriculture and a limited conception in some of what constitutes a tree and what constitutes appropriate tree management.

Figure 16: “Neglect brings benefits” The rewilding movement has been around for a while now in the UK – but in urban areas it needs to overcome the ingrained cultural concepts of areas being ‘overgrown’ and sites being ‘neglected’ – when that is what much of our rarer wildlife really needs. As with Fig. 15, if no-one gets around to mechanically removing the stump of a tree, good things can happen. In this case, a whitebeam was blown over on an industrial estate: these sorts of trees rarely come to be replaced when lost on such commercial land, in my experience. Fortunately, it’s replaced itself through regrowth – and it has become a mixed bush of hawthorn and whitebeam. Why the hawthorn? Because it was one of those whitebeam specimens grafted onto a hawthorn rootstock, so both have grown back post-failure. That our trees can come back in this way shows their resilience and we should make more use of that ability where it fits within the landscape.

Figure 17: “Harping on” As well as coppice re-growth, Nature has more to teach us about how to keep trees alive past their ‘sell-by date’. A harp tree is one that has slumped over but continues to grow on the ground. My local parks and woodlands contain quite a few harp trees that have occurred naturally – which makes one wonder why, if a valuable tree has a major defect at its base or a partially decayed root system, it’s not an arboricultural practice to arrange for the tree to be lain down on the ground and allow it to continue growing. The common objection when I mention this is that ‘kids will climb on the fallen trunk of the tree’ – like that is something we must always try to stop. Another objection tends to be that it gets in the way of the grass being cut. The more we take a ‘normative view’ of tree and site management, the more we miss out on our trees’ potential. Here, in a local woodland, an oak has fallen over – fortunately, there is also a gap in the canopy above the trunk. This fallen tree is already on its journey to becoming a harp tree: I wonder how many of these potential harp trees, in a good setting for their development, are just cut up and disposed of? Probably the vast majority in managed areas – such a shame, and it exhibits our real lack of imagination. My current favourite tree is a harp tree, situated near the top of Arnside Knott: it has developed around twenty stems and, being on the ground, is a tree I can actually climb!

Unbelievable Losses

My 7th TOT article on ‘Decline and Death’ touched upon the many trees I’ve found to have died whilst following up on the fate of trees, many of which have not come to be replaced. As this TOT series of articles comes to an end, I would like to give further emphasise to the extreme damage that is inflicted on a daily basis to individual trees and the many unnecessary losses of urban forestry assets (Fig.s 18-20). That I find this effect so often, whilst not finding many new trees being established, is a worry – and perhaps it is not that anomalous. You decide.

Figure 18: “Overkill” This time-lapse shows a very anomalous story. A new avenue of lime trees was established in a local public park, but they were planted far too densely – at around 3 metre centres – and I used to use this as an example of poor design with trees. This park subsequently won a restoration grant that facilitated some tree works – and this whole avenue was stripped back out again – probably not having been there for more than twenty years. It was ‘overkill’ to have planted so many trees in the first place – it was also ‘overkill’ to have felled them all, in a park that is really bare and featureless through much of its centre. I am sure someone would put up arguments for what was done if this case were enquired into – but at least one mistake was made – if not two. Having established these trees, surely thinning out this avenue, or even using a tree spade to move some of the trees to other areas of the park would have been a much more sustainable solution. I say this is an anomalous story, but I have just recently come across a large wooded area, planted by volunteers about fifteen years ago that is now destroyed for the building of houses. It’s urgent that we get such tree plantings right and defend them against such development pressures.

Figure 19: “The chainsaw fairies” When a publicly-owned tree is topped at the back of a small modern house and garden that features a PVC conservatory, I’m sure we would all like to conclude who the perpetrator is; as the only people with the motivation to do this sort of damage are the owners of said house and conservatory. Apparently, though, such circumstantial evidence is not enough to consider a prosecution – something that I think is anomalous in terms of justice. Pictured is an alder that was in a local churchyard – one of a row of trees that came to be topped to the rear of two of the neighbouring houses – shockingly, including the topping of three birch trees by the village’s cenotaph. This alder was topped on a Saturday, “when no-one was around” and, on my return, it had been felled – again, the vicar of the parish wasn’t around when that happened. As we can’t presume the guilt of the property owner in such cases, we ought to consider the possibility that this work was carried out at night by ‘chainsaw fairies.’ If you didn’t know, chainsaw fairies turn up to do tree work for free wherever a resident makes a wish for more light to their windows and less leaf litter in their gutters. Despite all the noise this tree cutting must make, it’s surprising how the neighbours claim not to have heard or seen anything – proving that it must have been fairy magic!

Figure 20: “Reverting to type” This image of the reversion of a variegated Norway maple I was going to include just as an example of reversion. Honestly, I don’t know why anyone bothers with ‘Drummondii’ as a cultivar, given that this ‘experiment’ has been tried many hundreds of times – always with the same result – the variegated foliage always reverts. However, as the TOT process involves telling the stories of trees, there can be major deviations in expected pathways – you know, anomalies… In this case, just at the time of putting this article together, I travelled passed this garden and found the tree had been topped – with no crown retained at all. I often tell my students that garden trees are a very important part of many urban forests in the UK – and that most of them are constantly under threat of poor management or destruction. Liberal and democratic people that we are in the UK, we allow such destruction of environmental assets to occur as part of home-owners’ liberties. Although the reverting foliage on this tree made it a “dog’s dinner”, it’s no improvement to have topped it, I would say. Perhaps the arborist was told to “remove all the green shoots”, and she/he found it too much of a faff and just removed all of the shoots?

During the strict ‘lockdown’ through March and early April this year, I took to taking the children for local walks in our peri-urban part of Lancashire – always taking the camera, of course. I made a collection of images of local oak trees that we found as our walks radiated out from our home – there were many magnificent old oaks to record in hedgerows, gardens, churchyards, and parks. But there were none – zero – new native oak trees anywhere we walked, outside of woodland. I live in a glorious landscape – but one that is essentially declining, from this brief analysis. It is partly for this reason that we have initiated an Arbor Day at Myerscough College – so new trees do get planted into the local landscape. Our current society often seems to be planning only for the short-term: sustainable tree planting for future generations needs more of us to be longer-term thinkers.

Urban Trees: “The Underdogs”

I do have an instinctive bias towards ‘the underdog’ – but I’m not so na?ve as to give unconditional love to all underdogs: some trees I find I can’t give my trust to (Fig. 21) – but I suppose that makes these trees someone else’s underdog. In general, if you work with and care for urban trees, you’re doing a great job: caring for something highly valuable that most laypeople severely undervalue: An urban forester is probably always someone who is not ‘going with the flow’ – but then the latter is associated with people who are not sincere, who have no true emotions, so that’s probably just as well.

Figure 21: “A ripping yarn” The strongest feedback I get about the TOT project is where my time-lapse images show a tree recovering from an injury or pruning wound. It must seem to many people that this is a positive news story – and perhaps gives the wish-fulfilling impression that Nature and the environment are capable of healing themselves without our intervention. I’m not so na?ve – but it can be surprising how different people interpret these sorts of images in very different ways. This image shows one of those dodgy Platanus clones that blighted urban tree planting in the UK in the 1980s – and which had split catastrophically to leave only two lateral branches. On my return, one might think “Wow – what an amazing recovery by that tree” – however, it is still one of those dodgy Platanus clones that one cannot trust to be structurally sound. For me, in an urban setting with targets, there’s not much joy to be had in watching a tree like this getting bigger – nor a Fraxinus ‘Raywood’ either…

Recording so many trees over time, some are developing a second and third chapter in their lives – as in Fig. 20. To finish, here’s a tree that featured in the first TOT article on physical resilience that was a great example of a tree coming back in that ‘underdog’ way – but which has come to be hacked down by a vandal (or vandals) two years later (Fig. 22 & 23). Having been more personally involved with this tree and using the image of its recovery from the dog biting in several of my lectures, this further damage to the tree feels more like ‘MURDER!’

Figures 22 & 23: “The stories continue…” Appearing in my first TOT article on physical resilience, this silver lime (Tilia tomentosa Moench) made an admirable recovery from damage to its stem caused by a dog goaded to bite it by an anti-social individual (Fig. 22). Sadly, this year, revisiting this park for other reasons, I found that this poor tree has been subject to a further violent attack – and of greater severity (Fig. 23). Someone had cut into the stem all the way around with a hatchet, machete or knife – and the tree’s stem had snapped at that point in an early summer squall – probably only about a week or so before I took these two images. Note that the stem below the cutting and failure point has already produced epicormic shoots. The normative view would be to fell the remains of this tree and start again – however, I’ve had much success in coaxing a damaged tree like this back to a good form by applying multiple doses of formative pruning. For this tree, and many others I have been tracking for my TOT images, the story may continue to develop in interesting ways.

And on that bombshell…

This is the last article in this series of ‘Trees Over Time’. I had contemplated a further article on trees in relation to development, of which I have quite a few related time-lapses – but it was just too depressing to put those images of death, destruction, bad design and ineptness together on the same page. “Something is rotten in the state of Denmark” - and in Warrington, Wimbledon, and Wolverhampton too, I’m sorry to report. I’m going to keep the best worst examples in that category for my book, I think.

I deeply enjoy the process of going back to so many trees to create these TOT images – each good time-lapsed situation makes a story – and the stories for many of these trees will continue for decades. I will be keeping this side-line of revisiting trees I have pictures of, for as long as I am able – as I’m rather addicted to finding out what happens in the next chapter of each tree’s story. Surprises await – and much learning…

Yours anomaly, Duncan.

References

Gibbs, J, Brasier C and Webber J (1994) Dutch Elm Disease in Britain; Research Information Note 252, Forestry Commission.

***THIS ARTICLE FIRST APPEARED IN THE SUMMER EDITION OF THE ARB MAGAZINE 2020 - MY MANY THANKS TO SARAH BRYCE FOR EDITING ALL THESE ARTICLES AND ALLOWING ME SO MUCH PAGE SPACE!***