Hazard tree recognition

Paul Forrestin Conservation & Ecology

TreeSurveys 3
Under the Occupiers Liability Act 1957 and 1984, there is a duty upon the occupier to take such care as is reasonable to ensure that bona fide visitors shall be safe from harm.

It is for this reason that I highlight the need for us all to understand why hazard tree recognition and the implementation of a basic tree survey and inspection report is of such great importance to us all as Sports facility managers. This will help to identify the three D issues - Dead, Diseased and Disorder - within the tree stock and produce a maintenance programme for the mature tree stock within your sports facility.

A tree survey and inspection report will also show your sports facility insurer that steps have been taken to reduce the risk of fallen branches or canopy failure onto target areas - paths, roads, buildings or even visitors and staff.

The value of trees can sometimes be completely overlooked and, all too frequently, tree management is simply forgotten and associated problems only arise when they have completely taken hold. How often have you walked under a tree and seen fallen branches, but never even thought to look up?

Sadly, a number of tragic, tree related accidents in recent years has highlighted the need for proper tree management under the care of the person or organisation responsible for the tree.

In July 2002, a city council were successfully prosecuted following the death of three people in two cars when a diseased Ash tree collapsed in December 1999.

TreeSurveys 1
Furthermore, section 3 of The Health and Safety at Work Act 1974 states: to ensure, so far as is reasonably practicable, that persons not in his employment who may be affected are not, thereby, exposed to risks to their health and safety.

Undertaking an annual inspection -both in and out of leaf - and following the advice given in the report can help your skilled maintenance teams to control the three D's which would lead to the risks associated with fallen branches and canopy failure. This not only aids the duty of care of the land occupier and obligations to the occupier's liability, but promotes sound ecological benefits and conservation efforts.

On golf courses in particular, tree maintenance should form an integral part of the course maintenance policy in order to further promote the playing characteristics and course character.

Lantra offer a basic one day Tree Inspection Training Course which aims to provide you with the knowledge to be able to identify a hazardous tree, determine the level of risk and then decide on an appropriate course of action and, furthermore, a three-day course which aims to provide specific tree inspection training at an advanced level for competent arboriculturists.

TreeSurveys 2
The type of survey conducted is quite methodical and usually carried out visually from ground level, although the survey could necessitate the need for a more specialist climbing inspection and the use of high technology devices such as decay detection systems.

As an example of a visual ground level inspection, you would note general observations (see table) of the tree reference number, species, size and age class, nature of defect (physiological and structural condition), level of risk (a hazardous tree only presents a risk if there is a 'target'), whether action is required and the level of urgency.

As a guide to the methodical process, you should follow a routine so that nothing is missed:

- Is the crown dense and full of leaves or perhaps showing obvious buds and twigs when dormant?
- Are the leaves large, green and undamaged from pest infestation?

TreeSurveys 4
An example of pest infestation would be leaf gall (see picture); the swelling of plant tissue caused by the infestation of a living organism, most often insects, mites, nematodes, bacteria, fungi or viruses.

Galls can form on any part of a tree and come in many shapes, sizes, colours and textures. Galls that are caused by insects or mites form in reaction to the laying of eggs, or the feeding of the insect that causes the gall. Most insect galls don't cause serious or long-term damage to an established tree. However, leaves will prematurely fall and, in immature trees, twig dieback can kill the tree. Twig dieback is a condition that occurs when new growth dies, in this case as the result of gall infestation.

- Does the tree crown contain deadwood, hanging and broken branches? (see picture).
- Are there any obvious cracks, rubbing branches or damage from maintenance equipment (usually mower equipment at the base) leaving the bark open to infection?
- Does the tree lean, particularly toward a target area (path, road or building)?
- Is there any evidence of fungus, disease or decay on the tree?
- Are the roots exposed in part or damaged, perhaps from maintenance equipment or excavations?
- Does the soil around the tree base show evidence of heave?

It can sometimes be difficult to notice the presence of cracks, splits and other defects from ground level, but they should be reported when you notice them.

Some trees can show evidence of quite apparent swelling around a decayed part of the tree and this is usually a sign of a process called 'adaptive swelling', where trees have the ability to strengthen themselves in areas of weakness. In this instance, the defect should be analysed by an appropriately qualified and indemnity insured arboriculturist.

If fungi is present on branches and is perceived to have caused weakness in the branch, then the recommendation for preventative pruning should be made.

A common sight nationwide within the canopy and climbing up the main stem of trees is ivy which, although can support a wide variety of wildlife and, in some instances, look attractive, can also hide defects. Although ivy does not actually kill trees itself, it will hamper the trees ability to adequately photosynthesise by blocking out light to the inner canopy and pose a greater burden to branches which, in time, will become prone to failure.

As previously mentioned, trees have the ability to strengthen themselves (adaptive swelling) in areas of weakness. So, trees growing in windy conditions may look misshapen or leaning, but will have adapted to the environment and problems usually arise when other trees have been removed.

TreeSurveys Table
Therefore a leaning tree is not always a problem, but caution should be aired when the tree is leaning over a target and, should the tree fail, then it will, of course, land on that target.

Fungal infections on the roots and stem of trees are usually evident in the form of fungal brackets. These are a sign that fungal mycelium is growing within the tree and, in some cases, a fungal bracket will show only 20% of the infection externally, with the remaining 80% of the infection within the roots and stem itself. Some of the fungi, particularly the ones that live on the stem base and the roots, can cause so much decay that there is a risk of the tree blowing over.

The inspection report should be presented in a clear manner which represents the findings of the survey, with all documents filed as points of reference during maintenance planning, with copies archived. This could make the difference between an effective defence or none at all in the case of litigation.

It is of great importance that the person undertaking the survey and inspection has a sound understanding of the relevant ecological issues and Acts of Parliament in place to protect our native flora and fauna.

Although it is permissible to disturb crows, magpies and pigeons at any time of year, and the majority of other species in order to preserve public health or safety, Schedule 1 of the Countryside and Rights of Way Act 2000 states that the disturbance of any birds covered in schedule 1, which includes seventy-nine less common species, may only be done under licence.

In the case of surveying ancient trees, the English Nature Specialist Method must be used to record the dependable habitat for that tree.

Recommendations, as noted in the survey report, should ideally direct minimal treatments in order to preserve ecological objectives and crown stabilisation in terms of decades opposed to non-ecological objectives.

After working as a greenkeeping apprentice, Paul Forrest joined the greenkeeping team at The Flaxby as Deputy Head Greenkeeper, and later became a company director for a Landscape and Horticultural contractors. In 2013, he rejoined The Flaxby and is currently studying the Foundation Degree Sports Turf Science through Myerscough College. The R&A awarded Paul a placement onto their Greenkeeping Scholarship programme through which he regularly exchanges advice and expertise regarding Golf Course sustainability and sound management practices alongside fellow R&A Scholars
Article Tags:
Conservation & ecology