Tree Management

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Introduction

Unlike cars or houses which need regular repair, trees are complex living organisms, which have their own natural defence and maintenance systems. Life, death and decay are part of the natural cycle of life, and this includes trees.

In forests and woodlands trees compete with each other and with many other living things for light, space, water and energy. The defence and maintenance system within the tree ensures its survival. In the forest, lower branches die and are shed, producing trees with long slender trunks. Weaker trees may die, fall down and decay. Storms may cause branches to break of and fall to the woodland floor, to decay and become hosts to many other living things. Dead branches and cavities can be important wildlife habitats for many species.

However, trees have been brought out of the forest and into the urban environment where we live and work. Also the encroachment of roads and buildings into the countryside has altered the trees’ natural environment.

Trees in urban areas have to live in an alien environment with soil conditions that lack the natural balance of water and nutrient supply required for normal growth. They have to compete for space, tolerate pollution from vehicles, poisoning from chemicals such as de-icing salt, and wounding by pruning requirements.

All this in addition to coping with natural threats such as viruses, disease, insects, mammals, birds, severe weather and other agents which damage trees. It is a miracle that trees even manage to survive!

Natural defects in trees and damage due to adverse weather that are not a problem in the forest can be a hazard in the urban environment. For these reasons trees in parks, gardens, streets and public spaces require extra maintenance to keep them in a safe and healthy condition. The extra maintenance is often called ‘tree surgery’. There is both a personal and public interest in keeping our trees healthy and long lived. The proper care of trees with an understanding of how they grow and defend themselves is called ‘Arboriculture’.

Tree work - Pruning

Pruning is carried out for a variety of reasons, not always for the benefit of the tree. Branches are often considered to be a nuisance or are causing an obstruction. Some pruning may be in the interest of tree health, public safety or both.

Trees should not be pruned if it is not necessary to do so since any cutting can weaken a tree and each pruning wound exposes vulnerable tissues, which may be colonised by wood decaying organisms. Pruning of a healthy tree usually results in the production of vigorous new growth which depletes the tree’s food reserves. In certain species the harder the pruning then the more vigorous the new growth, commonly referred to as epicormic growth, will be. Older trees do not tolerate pruning as well as younger ones and substantial pruning can be very damaging, particularly in species which are not naturally tolerant of cutting.
Very substantial reductions can be detrimental to tree health, because of the loss of foliage, functional tissues and the creation of large pruning wounds.
 

 
Pruning operations

Generally most trees that need to be pruned will require one, or a combination of the following pruning techniques.

Pruning aims to develop a strong and well balanced branch structure.

Crown Thinning: This is the removal of a small portion of the secondary and small live branches throughout the crown. Thinning should produce a uniform density of foliage around an evenly spaced branch structure and reduces the density of the crown without altering the shape and form of the tree. Crown thinning should generally only be applied if there is a specific management reason for doing - inappropriate or overzealous thinning operations can have a significant adverse impact on crown structure and condition.

Crown Lifting: This is the removal of the lowest small diameter branches and preparing of lower branches for future removal. Crown lifting should avoid creating large wounds on the main trunk of older trees as these may take many years to occlude. To avoid lack of balance after crown lifting the crown should be at least 2/3 of the total height of the tree.

Crown Reduction: This is the reduction of the crown of a tree, or the tree itself, whilst maintaining its natural shape and form as far as practicable. The ends of the branches should be removed back to a suitable growing point (i.e. internal lateral branches) and the diameter of the remaining branch should be at least 1/3 of the diameter of the branch that is removed.

Remember - pruning results in wounding and loss of live tissues, which impacts on the function and health of the tree system. Therefore tree works should always be planned and restricted to the work necessary to achieve the pruning objective. Pruning should be avoided during spring and autumn time when trees are moving and storing vital energy reserves throughout the tree.

 

British Standard 3998

Trees work - Recommendations

The Standard provides recommendations and guidance for arboriculturists, land managers, tree owners, contractors, planners, statutory undertakers, surveyors, and all others interested in the care, management, and pruning of trees.

British Standard 3998 gives recommendations and guidance on the principles to be applied to achieve a satisfactory standard of tree management, tree work and general tree care (arboriculutural) operations. The standard also sets out the potential legal constraints and restrictions to be considered before undertaking tree work. It follows, in sequence, the stages of planning and decision making processes, which are essential to make appropriate tree management recommendations.

British Standard 3998 recognises that there can be problems with trees in relation to people, property and other infrastructure. The standard sets out to assist those concerned with tree management and pruning to form balanced judgements.

British Standard 3998 was originally published in 1966 but the current (3rd) revision was found necessary to take account of current practice, legislation and industry research regarding the management of trees.

Copies of British Standard 3998 and other British Standards can be purchased from the British Standards Institute at the following address:
 
Head Office
389 Chiswick High Road
London
W4 4AL

BSI Website: http://www.bsonline.bsi-global.com/server/index.jsp (this is an external hyperlink)

For further information please contact the Tree Team in the Department of Planning and Environment Tel: 01329 236100 ext. 2442 or e-mail conservation@fareham.gov.uk.