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Welcome to The Green Man Arboricultural Consultancy

This website supports the consultancy business based in North Wales and which operates throughout the United Kingdom providing a wide range of arboricultural services including: home buyers tree reports, tree condition reports, development site surveys and reports, woodland assessment and management plans and general advice relating to trees.

For further information or to discuss your requirements please contact us on: 01978 821 851/ 07981 912 162 or via

Friday, 17 February 2012

Pests & Diseases: Parasitic Rot Types - Brown Rot

In November I created a post about a decay pathogen I had spotted on a mature beech tree. Following on from that post I would like to discuss the different types of parasitic rot that effect trees, starting with brown rots.

There are two cellular components in wood that are significant in allowing trees to achieve and maintain their size and stature. These are cellulose and lignin. Cellulose provides flexibility. It is the cell wall component that allows trees to withstand loading forces such as heavy snowfall and strong winds, and allows them to adapt to their environmental stimulus. Lignin provides rigidity and is the cell wall component that allows them to support themselves.

If a tree were to loose its cellulose it would become inflexible and the wood texture would be brittle. Loose the lignin and the tree can flex but looses its rigidity, its strengthening material. In arboriculture we say that cellulose provides tensile strength and lignin provides compressive strength.

Parasitic fungal decay pathogens (biological agents causing disease, and feeding on living wood) live off components of the cell wall and are selective about what cellular component they degrade, dependant on the rot type that they cause. Fungal pathogens are also selective about what part of the tree they degrade for example root rot, stem rot or branch rot.

First we will consider brown rots; brown rots degrade the cellulose in wood. The result as discussed above is a loss of tensile strength. The tree looses its ability to flex and the woody degradation caused by brown rots may result in brittle fractures.

If the fungal pathogen that causes a brown rot is associated with degradation of the roots of a tree, or the base of the stem, then the significance can be severe.

Arboriculturalists study decay pathogens in great detail. Fungal pathogens can be species specific, or effect a variety of tree species, sometimes being of a varying significance across the species. Aditionally trees have their own coping mechanisms and defences against pests and diseases which can seal off areas of decay and develop reactionary growth to compensate for the increased stress on their structure.

This is one of my favourite decay fungi, and brown rot fungus, Phaeolus schweinitzii. (Sorry, no common name!)

This fungus is associated with conifers. I have seen it on a variety of pines, cedars and spruce trees. The most incidences of it that I have recorded have been in conIfer plantations however I have also found it on several urban trees, i.e. trees growing in an urban environment.

The fungus is associated with degradation of the root systems and the decay can further extend up the main stem. Brackets are usually found on the ground around the root plate, growing directly off a root, or on the stem base or main stem.

It should be noted that the bracket, or fruiting body, of a fungus is just that, the fruit. The fungus itself lives within the tree.

As mentioned it is vital that arborists have a good understanding of the significance of pests and diseases, and good identification skills, to allow appropriate measures to be prescribed however from what we have discussed in this post it is clear that this fungus creates a serious risk of tree failure given its rot type and the part of the tree it degrades. This is what it can do to trees.

In the next post we will consider white and soft rots. For further reading I recommend the following book which is my favourite and most thumbed tree book: Principles of Tree Hazard Assessment and Management - David Lonsdale 1999 (DTLR ISBN 0 11 7533556)

Woodland Management - Emergence

I took a walk in my local woods this week with the dogs.

The woodland floor had been snow covered for about a week however a warm day and spell of rain put pay to the snow and revealed that the bluebells are making an appearance.

You can only see their leaf tips emerging at present but they are on their way. (This image is what we are all now waiting for!)

Woodland ground flora is at its most impressive in the spring. I like to walk in woodlands in spring to make the most of the wild flowers, and it is much easier to identify wild flowers when they are in bloom. More importantly much of the woodland flora does not persist into summer. This is significant to me as an arborist when I undertake woodland surveys.

Anyone who gardens will know that their garden appearance, and range of plants and flowers, differs widely from season to season. There is usually at least one plant that pops up in our garden each year that I had completely forgotten existed until it makes an appearance. It is much the same for woodland, every season is different. 

Although I have undertaken some woodland management for silvicultural purposes my involvement has been mainly centred on managing woodland for trees and wildlife; taking a holistic approach to maintain the system.

Woodland exists as a ecosystem. Each component of that system is dependant on the other components. Wild flowers and woodland ground flora are successful in woodlands as a result of the presence and density of the other flora and fauna, therefore any changes you make as part of woodland management can have a big impact on the success of the ground flora, and other woodland components.

Ideally I like to be able to monitor a woodland through spring and summer prior to developing a management plan and making any recommendations for work however at the least I strive to survey a woodland in Spring and note what ground flora is present, and how successful it is.

This information can be used to inform on where work is needed, and the extent and timing of the work that you do, to minimise its impact. The tree layers of the woodland are always present, and many shrubs are visible all year round.

Removing too many trees or shrubs can increase the light levels to the woodland floor. Woodland ground flora is use to a semi-shaded environment, happy with dappled sunlight. Increasing light levels can therefore be detrimental to its success.

Increasing light levels also encourages other plants to dominate such as brambles and bracken.

Dense vegetation that blocks any light from a woodland floor can also be detrimental to the development of ground flora as the environment becomes too dark.

Brambles, or natures barbed wire as I like to call it, can dominate an area quickly. Although bramble is a valuable plant that provides food and shelter, for many birds and small mammals, it can completely out-compete other ground flora. (It should be noted that anyone considering the removal of dense areas of bramble must consider the bird nesting season, there are many ground nesting birds in this country and bramble provides excellent shelter for them. When cutting back bramble you may expose a nest that once discovered cannot easily be re-protected and any disturbance may have an effect on the survival chances of the young.)

Maintaining appropriate light levels to the woodland floor also promotes natural regeneration of the tree species present in the woodland via seedlings that develop from fallen fruit.

Woodland management requires a sensitive and considered approach. If successful you may preserve the system and promote its self perpetuation.

The next time you walk in woods, hopefully this spring, have a look at the ground flora and see what is growing. You can then look at the other layers of vegetation such as shrubs, small trees (under-storey) and the canopy layer and see how they affect the light levels that reach the woodland floor.


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