An arborist is a professional in the practice of arboriculture, which is the management and maintenance of amenity trees. Work can include tree surgery and also care of shrubs, vines, and other perennial woody plants. An arborist is distinct from a forester, or from a logger. Those professions may have much in common, but the scope of work is different. Arborists frequently focus on health and safety of individual trees, or wooded landscapes, rather than managing forests or harvesting wood.
Scope of work
To work near power wires either additional training is required for arborists or they need to be Certified Line Clearance trimmers or Utility Arborists (there may be different terminology for various countries). There's a variety of minimum distances that must be kept from power wires depending on voltage, however the common distance for low voltage lines in urban settings is 10 feet
(about 3 metres
). (American National Standards Institute
Z.133- and International Brotherhood of Electrical Workers
Arborists who climb (as not all do) can use a variety of techniques to ascend into the tree. The least invasive, and most popular technique used is to ascend on rope. When personal safety is an issue, or the tree is being removed, arborists may use 'hooks', ('gaffs', 'spurs') attached to their boots with straps to ascend and work. Hooks wound the tree,leaving small holes where each step has been (Tree Care Industry Association -found at tcia.org).
An arborist's work may involve very large and complex trees, or ecological communities and their abiotic components in the context of the landscape ecosystem. These may require monitoring and treatment to ensure they are healthy, safe, and suitable to property owners or community standards. This work may include some or all of the following: planting; transplanting; pruning; structural support; preventing, or diagnosing and treating phytopathology or parasitism; preventing or interrupting grazing or predation; installing lightning protection; and removing vegetation deemed as hazardous, an invasive species, a disease vector, or a weed. Arborists may also plan, consult, write reports and give legal testimony. While some aspects of this work are done on the ground or in an office, much of it is done by arborists who climb the trees with ropes, harnesses and other equipment. Lifts and cranes may be used too. The work of all arborists is not the same. Some may just perform consulting; others may perform climbing, pruning and planting: a combination.
Arborists gain certification and qualifications in a variety of ways depending on location such as country. It is important you know what type of arborist you need as for instance not all climb nor do all write reports and consult.
In Australia education and training is stream lined country wide and referred to as AQF There are varying levels of qualification.
In USA a Certified Arborist (or 'CA') is a professional who has over three years experience and has passed a rigorous written test from the International Society of Arboriculture Other designations include Municipal Specialist, Utility Specialist and Board Certified Master Arborist (BCMA).
Trees may need pruning for health and good structure, for aesthetic
reasons, and to permit people to walk under them. They might also require other care to improve their chances for survival, including treatments in response to damage from biotic or abiotic factors. Trees in urban landscape settings are often subject to human and natural disturbances above and below ground, and in need of solutions provided by arborists. Timing or methods depend on the species of tree and the purpose of the work, and a thorough knowledge of local species and environments is necessary to determine the best practices. Trees may also require pruning
to keep them away from wires, fences and buildings.
There can be a vast difference between the techniques and practices of professional arborists and those (without adequate training) who simply "trim trees". Some practices of (uneducated) tree workers are considered unacceptable by modern arboriculture standards. One example of an "unacceptable" practice is called "topping", "lopping" or "hatracking", when entire tops of trees or main stems are cut off, causing detrimental effects; generally done by cross-cutting the main stem or leaders, leaving big flat topped stubs.
Pruning should only be done with a specific purpose in mind. Every cut is a wound, and every leaf lost is removal of some photosynthetic potential. Proper pruning can be helpful in many ways, but should always be done with the minimum amount of live tissue removed.
In recent years, research has proven that wound dressings such as paint, tar or other coverings are unnecessary and may harm trees. The coverings may encourage growth of decay-causing fungi. Proper pruning, by cutting through 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 through spraying, soil application, stem injections or spraying. 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 in technology and sophistication from practices of the past, and many current practices are based on knowledge gained through recent research, including the widely respected intensive work by the late Alex Shigo, considered as one "fathers" of modern arboriculture.
Legal issues in arboriculture
Depending on the jurisdiction, there are a number of legal issues surrounding the practices of arborists and of urban tree management in general, including boundary issues, public safety issues, "heritage" trees of community value; and "neighbor" issues such as ownership, obstruction of views, impacts of roots crossing boundaries, nuisance problems, disease or insect quarantines
, and safety of nearby trees.
Arborists are frequently consulted to establish the factual basis of disputes involving trees, or by private property owners seeking to avoid legal liability through the duty of care. Arborists may be asked to assess the value of a tree in the process of an insurance claim for trees damaged or destroyed, or to recover damages resulting from tree theft or vandalism. In cities with tree preservation orders an arborist's evaluation of tree hazard may be required before a property owner may remove a tree, or to assure the protection of trees in development plans and during construction operations. Homeowners who have entered into contracts with a homeowner's association (see also Restrictive covenants) may need an arborist's professional opinion of a hazardous condition prior to removing a tree, or may be obligated to assure the protection of the views of neighboring properties prior to planting a tree or in the course of pruning. Arborists may be consulted in forensic investigations where the evidence of a crime can be determined within the growth rings of a tree, for example. Arborists may be engaged by one member of a dispute in order to identify factual information about trees useful to that member of the dispute, or they can be engaged as an expert witness providing unbiased scientific knowledge in a court case. Homeowners associations seeking to write restrictive covenants, or legislative bodies seeking to write laws involving trees, may seek the counsel of arborists in order to avoid future difficulties.
Arborist training, reference materials, and continuing education
The study materials considered to be the reference canon for arborists seeking to advance from entry level to mastery of the trade in arboricultural services are the following:
- Arboriculture: Integrated Management of Landscape Trees, Shrubs, and Vines, 4th edition (Harris et al. ) - the standard text for introductory arboriculture, and the primary reference for working arborists.
- ANSI A300 standards for tree care operations (TCIA, all parts) - industry standards.
- ANSI Z133.1 standard for tree care operations (ISA) - industry standards.
- ANSI Z60 standard for nursery stock (ANLA) - industry standards.
- Best Management Practices (ISA, all topics)
- Plant Health Care for Woody Ornamentals (Lloyd et al.)
- Abiotic Disorders of Landscape Plants—A Diagnostic Guide (Costello et al.)
- Trees and Development: A Technical Guide to Preservation of Trees During Land Development (Matheny and Clark)
- Manual of Woody Landscape Plants (Dirr)
- An Illustrated Guide to Pruning, 2nd edition (Gilman)
- Principles and Practice of Planting Trees and Shrubs (Watson and Himelick)
- Arborists’ Certification Study Guide (Lilly)
- Plant Physiology (Kozlowski)
- Urban Soils: Applications and Practices (Craul)
- A New Tree Biology (Shigo) - the classic text by the man widely considered the father of modern arboriculture, Alex Shigo.
- The Landscape Below Ground; Parts I and II (Neely and Watson)
- Arboriculture and the Law (Merullo)
- Trees and Building Sites Conference Proceedings (Watson and Neely)
- The Art and Science of Practical Rigging (Donzelli et al.)
- A Photographic Guide to the Evaluation of Hazard Trees in Urban Areas (Matheny and Clark)
- Diseases of Trees and Shrubs (Sinclair et al.)
- Evaluating Tree Defects (Hayes)
- Guide for Plant Appraisal, 9th edition (CTLA)
- Insects That Feed on Trees and Shrubs (Johnson et al.)
- Tree Structure and Mechanics Conference Proceedings: How Trees Stand Up and Fall Down (Smiley et al.)
- Journal of Arboriculture
- Pesticide information: www.greenbook.net and www.pesticideinfo.org
- Urban Forestry: Planning and Managing Urban Greenspaces (Robert Miller)
- Natural Disaster Damage to vegetation
Other significant study materials and references for arborists include:
- USDA Soil Surveys
- Soil Science (Hausenbuiller)
- Urban Soil in Landscape Design (Craul)
- Built Environment (Bartuska)
- Design with Nature (McHarg)
- Principles and Applications of Soil Microbiology (Sylvia et al.)
- The Biology of Symbiotic Fungi (Cooke)
- Mycology - Plant Pathology Internet Guide Book (Kraska)
- Forest Entomology: Ecology and Management (Coulson & Witter)
- Plants of the Pacific Northwest (Pojar), or similar local reference
- Trees of Seattle (Jacobson), or similar local reference
- Natural Vegetation of Oregon and Washington (Franklin), or similar local reference
- The Use and Significance of Pesticides in the Environment (McEwen)
- The Body Language of Trees (Mattheck)
- Trees (Coombes)
- Wild Neighbors: The Humane Approach to Living with Wildlife (HSUS)
- IPM World Textbook (Radcliff, online)
- The Tree Care Industry Association, formerly the National Arborist Association, is a public and professional non-profit organization for the arboriculture field. It has more than 2,000 member companies representing over a dozen countries. TCIA's Accreditation program certifies that tree care companies that have been inspected and accredited based on adherence to industry standards for performance and safety; maintenance of trained, professional staff; and dedication to ethics and quality in business practices. In addition, they provide safety and educational programs, guidelines for tree service operations, ANSI A300 tree pruning standards, and consumer resources.
- 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 for those who work near power lines, and Certified Arborist/Municipal Specialist for those who deal mostly with community trees. 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 in various instances where a particular authority on trees is necessary for consequent actions.
- In the UK, the principal organisation representing arborists is the Arboricultural Association The association maintain a register of consultants who have demonstrated a high level of technical arboribultural knowledge, and operate an Approved Contractor scheme. This scheme assesses both the technical competence and business practices of arboricultural contractors. Searching for approved contractors is possible through the tree-care.info 'Find an Arborist' area and the 'UK Arborist Directory'
- The European Arboriculture Council is a European group of arboriculture organizations from various countries.
- Plant Amnesty is a public education and advocacy group, based in Seattle, dedicated to promoting proper pruning methods. Founded in 1987, Plant Amnesty became an international resource for arborists and their clients in the mid 1990's.
Some noteworthy arborists include:
- John Chapman - pioneering U.S. frontier nurseryman and orchardist, commonly known as Johnny Appleseed.
- Chuck Leavell - two-time recipient of the Georgia Tree Farmer of the Year award, and author of the children's book, The Tree Farmer. In 2006 Leavell was appointed by Governor Sonny Perdue to the Georgia Land Conservation Council. He is also an accomplished jazz pianist and keyboardist for the Rolling Stones.
- Alex Shigo - the father of modern arboriculture.
- Cass Turnbull - founder of Plant Amnesty, a non-profit education and advocacy group, and author of pruning and gardening books.
- Benjamin White - a working arborist until injured in a fall from a tree, Benjamin White became an environmental activist, worked as bosun of the Sea Shepherd, and created the sea turtle costumes worn at the anti-WTO protests in Seattle during 1999.
- Liam McGough - a contestant on the British version of Big Brother
Notes and citations