Absolutely Barking!

Bark Poster

A number of people have asked me to produce the bark gallery on the right as a high resolution poster - it can be
downloaded here
It's an A2  PDF (which is 4 times A4, but the will resize to A3 or A4).


Absolutely Barking!


Examples of different bark types trees which I've photographed on the patch
Bark is like almost everything in nature – the more you look the more you see. If you walk through a wood you will, of course, be aware of the trees, but only have a vague sense of the variety of bark. Once you stop to look you’ll see that every tree species has its own kind of bark, and even amongst trees of the same species – no two are alike.

My latest patch project has been to photograph an example of the bark of each of the tree species on the patch – the result being the photos on this page. A quick glance through these is enough to show the range of bark types, colours and textures to be found - as well as their beauty . Some are rough, others smooth, some have vertical fissures others horizontal. Still others are patterned with ridges, sploges or square-shaped markings.

That no two trees are alike is well demonstrated by these examples of sycamores I've found on the patch. These are roughly ordered by age of tree which also gives an indication of how bark can vary throughout the tree's lifetime

Layers of the cross section of a tree
Tree bark and human skin, have a lot in common. They are both outer layers with a role in protecting the tissues beneath, and both are unique to the individual. Each fingerprint is famously unlike any other and no two trees have exactly identical bark.


There are a whole host of organisms, which share the tree's habitat and would like to 'get their hands on' the nutritious tree tissues. For this reason the tree has to invest a lot of resources on protection - hence bark. 

The outermost layer of the tree is made up of dead cork cells - this is the part we can see and touch. Cork protects the tree by helping to prevent water loss and insect / pathogen attack.  These cells are air-filled which helps insulate the tree and also accounts for the lightness of bark.


Why is tree bark so variable?

Different tree species occupy different ecological niches and each one has its own way of ‘going about things’ - this effects the kind of bark it has.

Beech, for example, has smooth bark which helps the tree avoid ‘hangers on’ -  ivy, mosses, insects etc find it difficult to gain a foothold. This smoothness has a cost, however – the bark must be produced slowly so the growth rate of the tree is limited and injuries are slow to heal.

Oak bark grows much faster than that of Beech, helping the tree repair injury sites and retain moisture. Again this comes at a cost – rapid growth causes the bark to crack, so harbouring insects and other pests. The Oak, therefore, has to counter these threats by making the bark less palatable and so produces protective chemicals such as tannins (which comes at metabolic cost).

Birch trees grow in damp environments and so are prone to lichen and moss infestation.  Therefore, to help shed these plants birches, have thin bark which peels easily.

Only a few species are like the Beech, in maintaining smooth, unbroken bark for their entire lifespan. The outer bark continues to grow at the same rate  as the increasing circumference of the tree. Most species reach a point where their wood is growing faster than the bark — and so the wood pushes outward against the bark - causing cracks, fissures etc. The specific characteristics of the specie's bark are partly a result of the way the it responds to this pressure.


Patch bark gallery

Alder
Ash
Aspen

Beech
Blackthorn
Cherry

Common Lime
Downy Birch
English Oak

Goat Willow
Hawthorn
Hazel

Holly
Hornbean
Horse Chestnut

Larch
Leyland cypress
Lombardy poplar

Juniper
Magnolia
Mountain ash

Norway spruce
Rhododendron
Rose (Dog Rose)

Scots pine
Sequoia
Silver birch

Sycamore
Turkey oak
Weeping willow

White poplar
Wych elm
Yew


So I’m looking at the bark of a tree – can I say why the bark like it is? Is it possible to say what has determined why this particular tree has this particular pattern. Well, it’s almost certainly, not possible, to account for every minute detail of the bark, some of it will probably be entirely random.

In a previous post on moth camouflage I found it a fascinating exercise to try to consider what might be the factors at play in determining the markings on a moths wing. A similarly interesting question concerns tree bark. 

This won’t be a complete list of factors  (and some of these factors may overlap, amount to same thing as other factors, or indeed not be relevant)

Species factors                     
Those that are common to all individuals of a given species and so have determined the way the tree has evolved
Environmental factors - influenced by the tree's distribution, habitat and the ecological niche it occupies
Climate -  how wet, dry, windy, sunny etc
Tree structure - size, shape
Interaction with other species -  protection from epiphytes, parasites,  herbivores, pathogens
Interaction with other species - non-protection  mycorrhizal fungi for example
Protection, physical - from extremes of temperature, resistance to fire, against water loss, impacts etc
Protection, chemical – chemicals protecting against insects, fungi bacteria etc
Bark chemical composition – may influence bark colour for example
Bark physical composition  – e.g how much air in the cells, this may also effect colour
Response to injury or infection 
How is bark shed by the tree
Bark layer composition – 3 layers of outer bark phellem, phellogen, phelloderm – and 2 of the inner, phloem, vascular cambium – how much of each is present and in what form
Other parts of the tree -  leaves, flowers, seeds may well have an influence
‘Lifestyle’ – e.g. is it deciduous, when does it come into leaf
Speed of growth – see the examples of beech and oak above
Photosynthesis – how much bark photosynthesis takes place – which will effect presence or absence 
of Lenticles (the pores which allow gas exchange through the bark)
How Long lived
Which part of the tree – are we looking at  - the lower trunk, a branch or a twig
Feedbacks – for example,  the overall weight of the bark will affect the structural properties of the tree which may be a factor which feeds back to influence the properties of the bark

Individual factors   
No two trees of the same species are exactly alike, so overlaying the species factors  will be factors effecting the bark of the individual                        

Location – in which part of the species' range is the tree growing and in which habitat within the  species' habitat range.
Neighbours – what other individuals of other species and the same are growing / living nearby
History – what has happened during the tree’s lifetime
  • Weather
  • Lighting strike
  • Herbivore / pest attack
  • Woodpecker holes, etc, etc
Age
Genetics

As we saw with the examples of Oak and Beech, and with moth camouflage, there are competing factors which are traded of against each other and there will, in fact be a whole network of interactions in constant flux.

To take a step back for a moment - tree bark and moth's wing aren't particularly special in this respect. It's probably true to say that most things are the way they are due to a large web of interacting factors.

 ...or to put it more simply - things are the way they for lots of reasons (which is a statement so blindingly obvious it calls for a "no sh*t Sherlock!")


This tree on the patch was probably struck by lightning. It is burned out and almost completely hollow inside.
The fact that it continues to grow, seemingly healthily, is testament to the fact that most of the life of the tree is in the inner bark
As an experiment I was interested to see if I could distill bark patterns down to something more simple as a kind of identification guide -  I don't think it's particularly successful - but I rather like the design!
Sycamore, Aspen, Silver birch, Alder, Oak, Cherry
 


Recent Patch Sightings
4/2 - 110 Pink footed Geese - north
6/2 - Song thrush, Starling, Great tit, Coal tit, Dunnock now in song
6/2 - First spring flowers - Opposite Leaved Golden Saxifrage
7/2 - 2 Willow tit, 3 Roe Deer
8/2 - Scarlet Elf Cup

Scarlet Elf Cup
Get this

Comments

  1. This is totally brilliant! Beautiful and helpful, too. Brings the eye to the tree in a different way. Thank you.

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  2. Fabulously informative and superb quality photos.

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  3. Very interesting blog especially the photos, which are a useful identification tool. I too am fascinated by the patterns on bark, especially London Plane, which is ever changing as it peels. In our local park their bark is green with chlorophyll/lichen; when it rains the colour is highlighted and contrasts beautifully with the newer, orange bark. I love to paint trees, some of my watercolours can be seen at www.karenhumpage.turnpiece.net

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    1. Thanks Karen - I just checked out your tree paintings - superb! - I've got a couple of my paintings on this blog as well

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  4. This is a great article / research! Really enjoyed it, and very usefull & interesting. i shared it on my FB page and have had great feedback for you Thankyou

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  5. Great article. Short and to the point. Just the facts and well presented. Gonna go practice now. Cheers !!

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  6. A great resource - thanks for sharing

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  7. Fantastic article Phil! Glad to see I'm not the only one! Working on something similar myself at the moment

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  8. Wonderful article. Really, really useful. And the photos are beautiful - the gallery would make a fabulous poster - any chance?

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  9. This is brilliant. Many thanks. We have 4 hectares here in eastern Portugal that we're encouraging to develop as a food forest. We still have a few unidentified trees where this will be a great help.

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    1. Hi John - thanks whereabouts in Portugal? - I used to live in Braga, Cheers, Phil

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    2. Great photos and id's. I was wondering about one I saw a few weeks ago - Aspen!
      Cheers

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    3. Yes, I noticed it was blogspot.pt. We're in the foothills of Monsanto, near Idanha a Nova.

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  10. This is brilliant. Many thanks. We are working on 4 hectares here in eastern Portugal, encouraging its development as a food forest and we still have a couple of unidentified species. This will be a great help.

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  11. Brilliant Phil...every tree is an individual and love the detective approach to bark....cheers jon

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  12. wow!
    Better than many of published "Tree Identification" books commercially available.
    Thanks for putting your time and infinite knowledge to this informative page!

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  14. Curious if you used any spatial analyses to compare bark morphology. It seems like there could be some diagnostic combinations of bark characters that would help separating out a good number of species. Could be a very valuable contribution to winter tree ID.

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  15. This is one of the most beautifully written and informative posts I have ever come across. As a landscape designer, I find this extremely useful and amazing! Thank you for sharing!

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  16. This poster is awesome! Thank you so much for creating and sharing it!

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  17. So helpful, thank you very much. I am studying RHS Level 2 and your explanations have been fab. Michelle .

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  18. thanks for that, you convey a lot of information in a wonderfully accessible and easy going manner with beautiful images. Put a happy smile on my face.

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  19. I need to look at this page once in a while, as it's so brilliant information, thank you for all the work gone into this Phil.

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