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An arborist (or tree surgeon) is a professional who manages and maintains trees (generally in an urban environment). This can include planting, pruning, structural support, the treatment of disease, insect, or abiotic disorders, lightning protection, and tree removal. It also can include planning, consulting, report writing and even legal testimony. Because trees provide many benefits to the landscape and to people, but they are also very large, heavy, and complex organisms, they require monitoring and care to ensure survival and safety in the human landscape.
Cultural practices
Trees may require pruning to keep them away from wires, fences and buildings, to improve long-term health and/or structure, for aesthetic reasons, and to permit people to walk and sit under them. They might also require other care to improve their chances of survival and longevity, or treatments in response to damage from biotic or abiotic factors. Trees in urban landscape settings are often subject to human disturbances above and below ground, as well as natural disturbances. Timing or methods depend on the species of tree and the purpose of the work. A thorough knowledge of local species and environments is necessary to determine the best practices.
There can be a vast difference in the techniques and practices of professional arborists and those who simply "trim trees". Many common practices of tree workers are considered unacceptable by modern arboriculture standards. One common abuse of trees is a practice called "topping", "lopping", or "hatracking", in which the outer part of the crown or the entire top of the tree is cut off. This has several detrimental effects. When all of the foliage is removed, the tree is left without the ability to produce food through photosynthesis. It must use stored energy to produce a flush of new growth to replace what was removed. The large internodal cuts are much more prone to decay than proper pruning cuts, and the subsequent abundance of sprouts arise around this area of decay, as well as usually being poorly attached, overcrowded, and weaker due to rapid growth.
Pruning should only be done with a specific purpose in mind. Every cut is a wound, and every leaf lost is removal of some amount of photosynthetic ablility. Proper pruning can be very helpful in many ways, but should always be done with the minimum amount of live tissue removed for the individual situation.
In recent years, research has proven that wound dressings such as paint, tar or other coverings are unnecessary and may be harmful to the tree. The coverings may actually encourage the growth of decay-causing fungi. Proper pruning, by cutting the branches at the right location, can do more to limit decay than wound dressing.
Chemicals can be applied to trees for insect or disease control either through spraying (though this can become impossible with very large trees), soil application, or stem injections when necessary. Compacted or disturbed soils can be improved in various ways.
Arborists can also assess trees to determine the health, structure, safety or feasibility within a landscape and in proximity to humans. Modern arboriculture has progressed a great deal in technology and sophistication from practices of the past, and more of the practices are based on knowledge gained through recent research.
Arborist organizations
The International Society of Arboriculture, a non-profit organization, maintains a list of ISA Certified Arborists who have passed a written exam and demonstrated a basic level of knowledge in arboriculture. There are also additional classifications of certified arborists with Certified Arborist/Utility Specialist and Certified Arborist/Municipal Specialist. Other certifications exist for Certified Tree Workers, and the highest level of certification, the Board Certified Master Arborist.
The American Society of Consulting Arborists is an organization whose membership is exclusive to those with either a certain level of industry experience, plus higher educational experience or continuing education; some members may achieve a higher status by fulfilling the requirements to become a Registered Consulting Arborist. Consulting arborists generally specialize in the areas of ethics, law, land planning and development, and tree valuation, among others. Consulting arborists are often called on for legal testimony and report writing for various instances where a particular authority on trees is necessary for consequent actions.
Legal issues
Depending on legal jurisdiction, there are a number of legal issues surrounding the practices of arborists and of urban tree management in general, including:
- Ownership of trees on or near boundaries - neighbours may have legal rights regarding trees which adjoin or overhang their property.
- "Right to light" - some jurisdictions grant property owners rights to enjoy a "reasonable" amount of sunlight, and neighbouring trees which deny this may be subject to trimming or felling as a consequence.
- Structural impact - the growth of tree roots (or their removal) may affect the stability of nearby walls or building foundations. Equally, unstable, diseased or dead trees may fall, causing structural damage or personal injury.
- Control of disease - in an attempt to control epidemics of tree diseases or agricultural pests, some jurisdictions may require property owners to ensure their trees are healthy and that rot and disease issues are addressed.
- Conservation - in many locations, certain trees are protected (often on a basis of species or size), requiring a specific permission be obtained before they are felled or radically trimmed.
- Safety - property owners are generally liable for injuries arising from unsafe trees or tree branches, and may also be liable for the safety of arborists working on their trees.
External links
- International Society of Arboriculture
- American Society of Consulting Arborists
- Tree Care Industry Association
- European Arboricultural Council
- Treebuzz.com Discussion forum and source of information for arborists and tree climbers from around the world
- Arboristsite.com - Online forum of arborist and related professions.
"Arborist"