Arborists generally focus on the health and safety of individual plants and trees, rather than managing forests or harvesting wood (silviculture or forestry). An arborist's scope of work is therefore distinct from that of either a forester or a logger.[citation needed]
In order for arborists to work near power wires, either additional training is required or they need to be certified as a Qualified Line Clearance Arborist or Utility Arborist (there may be different terminology for various countries). There is 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).[1]
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. There are two common methods of climbing, Single Rope System (SRS) and Moving Rope System (MRS). When personal safety is an issue, or the tree is being removed, arborists may use 'spikes', (also known as 'gaffs' or 'spurs') attached to their chainsaw boots with straps to ascend and work. Spikes wound the tree, leaving small holes where each step has been.[citation needed]
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 perform tree services and 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 provide a consulting service; others may perform climbing, pruning and planting: whilst others may provide a combination of all of these services.[2]
Qualifications
An arborist disassembling a tree using a crane and bucket
Arborists gain qualifications to practice arboriculture in a variety of ways and some arborists are more qualified than others. Experience working safely and effectively in and around trees is essential. Arborists tend to specialize in one or more disciplines of arboriculture, such as diagnosis and treatment of pests, diseases and nutritional deficiencies in trees, climbing and pruning, cabling and lightning protection, or consultation and report writing. All these disciplines are related to one another and some arborists are very well experienced in all areas of tree work, however not all arborists have the training or experience to properly practice every discipline.[citation needed]
Arborists choose to pursue formal certification, which is available in some countries and varies somewhat by location. An arborist who holds certification in one or more disciplines may be expected to participate in rigorous continuing education requirements to ensure constant improvement of skills and techniques.[citation needed]
In Australia, arboricultural education and training are streamlined countrywide through a multi-disciplinary vocational education, training, and qualification authority called the Australian Qualifications Framework, which offers varying levels of professional qualification. Government institutions including Technical and Further Education TAFE offer Certificate III or a diploma in arboriculture as well as some universities.[3][4] There are also many private institutions covering similar educational framework in each state. Recognition of prior learning is also an option for practicing arborists with 10 or more years of experience with no prior formal training. It allows them to be assessed and fast track their certification.[citation needed]
In France, a qualified arborist must hold a Management of Ornamental Trees certificate, and a qualified arborist climber must hold a Pruning and Care of Trees certificate; both delivered by the French Ministry of Agriculture.[5][6]
In the US, a Certified Arborist (CA) is a professional who has over three years of documented and verified 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). The USA and Canada additionally have college-based training which, if passed, will give the certificate of Qualified Arborist. The Qualified Arborist can then be used to offset partial experience towards the Certified Arborist.
Tree Risk Assessment Qualified credential (TRAQ), designed by the International Society of Arboriculture, was launched in 2013. At that time people holding the TRACE credential were transferred over to the TRAQ credential.[citation needed]
In Canada, there are provincially governed apprenticeship programs that allow arborists' to work near power lines upon completion. These apprenticeship programs must meet the provincial reregulations (For example, in B.C. they must meet WorkSafeBC G19.30), and individuals must ensure they meet the requirements of the owner of the power system.[citation needed]
Cultural practices
Arborists may use specialised vehicles to gain access to trees, such as this Unimog equipped with a power take-off driven woodchipper
Trees in urban landscape settings are often subject to disturbances, whether human or natural, both above and below ground. They may require care to improve their chances of survival following damage from either biotic or abiotic causes. Arborists can provide appropriate solutions, such as pruning trees for health and good structure, for aesthetic reasons, and to permit people to walk under them (a technique often referred to as "crown raising"), or to keep them away from wires, fences and buildings (a technique referred to as "crown reduction").[7] Timing and methods of treatment depend on the species of tree and the purpose of the work. To determine the best practices, a thorough knowledge of local species and environments is essential.[citation needed]
There can be a vast difference between the techniques and practices of professional arborists and those of inadequately trained tree workers. Some commonly offered "services" are considered unacceptable by modern arboricultural standards and may seriously damage, disfigure, weaken, or even kill trees. One such example is tree topping, lopping, or "hat-racking", where entire tops of trees or main stems are removed, generally by cross-cutting the main stem(s) or leaders, leaving large unsightly stubs. Trees that manage to survive such treatment are left prone to a spectrum of detrimental effects, including vigorous but weakly attached regrowth, pest susceptibility, pathogen intrusion, and internal decay.[8]
Pruning should only be done with a specific purpose in mind. Every cut is a wound, and every leaf lost is removal of photosynthetic potential. Proper pruning can be helpful in many ways, but should always be done with the minimum amount of live tissue removed.[9]
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 [10]
Chemicals can be applied to trees for insect or disease control through soil application, stem injections or spraying. Compacted or disturbed soils can be improved in various ways.[citation needed]
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. Many current practices are based on knowledge gained through recent research, including that of Alex Shigo, considered one "father" of modern arboriculture.[11]
Legal issues
Depending on the jurisdiction, there may be a number of legal issues surrounding the practices of arborists, including boundary issues, public safety issues, "heritage" trees of community value, and "neighbour" issues such as ownership, obstruction of views, impacts of roots crossing boundaries, nuisance problems, disease or insect quarantines, and safety of nearby trees or plants that may be affected.[citation needed]
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.[12] Arborists may be asked to assess the value of a tree[13] in the process of an insurance claim for trees damaged or destroyed,[14] or to recover damages resulting from tree theft or vandalism.[15] 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. Carrying out work on protected trees and hedges is illegal without express permission from local authorities,[16] and can result in legal action including fines.[17] Homeowners who have entered into contracts with a Homeowner's association (see also Restrictive covenants) may need an arborists' 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.[18] 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.[19]
Before undertaking works in the UK, arborists have a legal responsibility to survey trees for wildlife, especially bats, which are given particular legal protection. In addition, any tree in the UK can be covered by a tree preservation order and it is illegal to conduct any work on a tree, including deadwooding or pruning, before permission has been sought from the local council.[citation needed]
Organizations
Australia Limited, a non-profit organisation, is a national organisation promoting and representing tree workers, arborists, professional tree management and urban forestry throughout Australia and the Asia-Pacific region.[20]
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.[citation needed]
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.[21] 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.[citation needed]
The American Society of Consulting Arborists is an organization whose membership is exclusive to those with 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.[22] 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 professional body representing the sector is the Institute of Chartered Foresters. The trade body representing arborists is the Arboricultural Association. The association maintains a register of consultants who have demonstrated a high level of technical arboricultural knowledge, and operate an Approved Contractor scheme. This scheme assesses both the technical competence and business practices of arboricultural contractors.
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-1990s.[23][24]
In literature
The protagonist in Italo Calvino's novel The Baron in the Trees lives life on the ground as a boy and spends the rest of his life swinging from tree to tree in the Italian countryside. As a young man he helps the local fruit farmers by pruning their trees.[citation needed]
Notable arborists
Some noteworthy arborists include:
Francis A. Bartlett – founded The Bartlett Tree Experts Co., the world's leading scientific tree and shrub care company in 1907.
John Chapman – pioneering U.S. frontier nurseryman and orchardist, commonly known as Johnny Appleseed.
Sebastian Junger – author of Perfect Storm and War. Previous to becoming a journalist, Sebastian was an arborist in Massachusetts.
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.[26]
Alex Shigo – considered the father of modern arboriculture.
David Mitchell - Devon born tree inspector and veteran tree expert
Friendship Oak on the campus of Southeastern Louisiana University is hundreds of years old. Like other mature spreading oaks, Friendship Oak is maintained by arborists to prevent the limbs from growing into the ground.
Arboriculture is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants. The science of arboriculture studies how these plants grow and respond to cultural practices and to their environment. The practice of arboriculture includes cultural techniques such as selection, planting, training, fertilization, pest and pathogen control, pruning, shaping, and removal.
Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots.
Urban forestry is the care and management of single trees and tree populations in urban settings for the purpose of improving the urban environment. Urban forestry involves both planning and management, including the programming of care and maintenance operations of the urban forest. Urban forestry advocates the role of trees as a critical part of the urban infrastructure. Urban foresters plant and maintain trees, support appropriate tree and forest preservation, conduct research and promote the many benefits trees provide. Urban forestry is practiced by municipal and commercial arborists, municipal and utility foresters, environmental policymakers, city planners, consultants, educators, researchers and community activists.
Girdling, also called ring-barking, is the circumferential removal or injury of the bark of a branch or trunk of a woody plant. Girdling prevents the tree from sending nutrients from its foliage to its roots, resulting in the death of the tree over time, and can also prevent flow of nutrients in the other direction depending on how much of the xylem is removed. A branch completely girdled will fail and when the main trunk of a tree is girdled, the entire tree will die, if it cannot regrow from above to bridge the wound. Human practices of girdling include forestry, horticulture, and vandalism. Foresters use the practice of girdling to thin forests. Extensive cankers caused by certain fungi, bacteria or viruses can girdle a trunk or limb. Animals such as rodents will girdle trees by feeding on outer bark, often during winter under snow. Girdling can also be caused by herbivorous mammals feeding on plant bark and by birds and insects, both of which can effectively girdle a tree by boring rows of adjacent holes.
The International Society of Arboriculture, commonly known as ISA, is an international non-profit organization headquartered in Atlanta, Georgia, United States. The ISA serves the tree care industry as a paid membership association and a credentialing organization that promotes the professional practice of arboriculture. ISA focuses on providing research, technology, and education opportunities for tree care professionals to develop their arboricultural expertise. ISA also works to educate the general public about the benefits of trees and the need for proper tree care.
Alex L. Shigo was a biologist, plant pathologist with the United States Forest Service whose studies of tree decay resulted in many improvements to standard arboricultural practices. He travelled and lectured widely to promote understanding of tree biology among arborists and foresters. His large body of primary research serves as a broad foundation for further research in tree biology.
Ulmus 'Frontier' is an American hybrid cultivar, a United States National Arboretum introduction derived from a crossing of the European Field Elm Ulmus minor with the Chinese Elm Ulmus parvifolia in 1971. Released in 1990, the tree is a rare example of the hybridization of spring- and autumn-flowering elms. Tested in the US National Elm Trial coordinated by Colorado State University, 'Frontier' averaged a survival rate of 74% after 10 years.
Tree topping is the practice of removing whole tops of trees or large branches and/or trunks from the tops of trees, leaving stubs or lateral branches that are too small to assume the role of a terminal leader. Other common names for the practice include hat-racking, heading, rounding over, and tipping. Some species of trees are more likely to recover from topping than others. There are alternatives to topping that can help to achieve the same goals without damaging trees.
The Certified Arborist credential identifies professional arborists who have a minimum of three years' full-time experience working in the professional tree care industry and who have passed an examination covering facets of arboriculture. The Western Chapter of the International Society of Arboriculture (ISA) started the certification program in the 1980s, with the ISA initiating it in 1992.
Tree Line USA is a program sponsored by the Arbor Day Foundation in cooperation with the National Association of State Foresters which recognizes public and private utilities across the United States that demonstrate best practices that protect and enhance America's urban forests.
A branch collar is the "shoulder" between the branch and trunk of woody plants; the inflammation formed at the base of the branch is caused by annually overlapping trunk tissue. The shape of the branch collar is due to two separate growth patterns, initially the branch grows basipetally, followed by seasonal trunk growth which envelops the branch.
Tony Kirkham MBE VMH is the former Head of Arboretum, Gardens & Horticulture Services, Royal Botanic Gardens, Kew.
The Davey Tree Expert Company, also known as Davey Tree, is a North American employee-owned corporation. The company's main services are research driven tree services, grounds maintenance and environmental consulting services for residential, utility, commercial and environmental partners in the United States and Canada. Davey has employees throughout the United States and Canada.
A whoopie sling is an easily adjustable rope sling designed for tree pruning or tree removal. The whoopie sling works by wrapping the sling around the trunk of a tree or a heavy load bearing limb and pulling the end of the rope within the sling through a spliced choker. By adjusting the size of the eye in the rope through the choker the user is able to adjust the length of the sling constricting around the tree without needing knots.
The European Arboricultural Council (EAC) based in Bad Honnef, Germany is a forum where delegates from a wide range of arboricultural organizations throughout Europe meet. The goal of the EAC is to elevate the status and to raise the professional level of competence within arboriculture. This objective is carried out by liaising on matters ranging from research and education to successful tree establishment and the improvement of safe working practices.
The Master Arborist or Board Certified Master Arborist credential identifies professional arborists who have attained the highest level of arboriculture offered by the International Society of Arboriculture (ISA) and one of the two top levels in the field. There are several paths to the Board Certified Master Arborist, but typically on average each has been an ISA Certified Arborist a minimum of three to five years before qualifying for the exam. The certification began as a result of the need to distinguish the top few arborists and allow others to identify those with superior credentials. The ISA added specialty certifications of Utility Specialist, for those maintaining vegetation around electric utility wires, Municipal Specialist, for those with additional experience managing public urban trees.
Trees can live for a long time but eventually die, either from natural causes or killed by man. Ill-health of trees can be diagnosed, and early treatment, pruning or felling to prevent the spread may result in timber stocks and amenity trees being saved. Tree owners and Arborists/arboriculturists need to be aware of the risk posed by hazardous trees. Construction projects sometimes avoidably damage trees.
A tree fork is a bifurcation in the trunk of a tree giving rise to two roughly equal diameter branches. These forks are a common feature of tree crowns. The wood grain orientation at the top of a tree fork is such that the wood's grain pattern most often interlocks to provide sufficient mechanical support. A common "malformation" of a tree fork is where bark has formed within the join, often caused by natural bracing occurring higher up in the crown of the tree, and these bark-included junctions often have a heightened risk of failure, especially when bracing branches are pruned out or are shaded out from the tree's crown.
A branch attachment is where a branch is attached to the trunk of a tree. Three types of branch attachment are recognized due to differences in the anatomical position of buds that form them. Two key components contribute to the mechanical strength and toughness of the attachment: interlocking wood grain at the top of the attachment and an embedded knot that often lies within the attachment. A common malformation of a branch attachment is the inclusion of bark within the join, which can weaken the attachment.
Tree care is the application of arboricultural methods like pruning, trimming, and felling/thinning in built environments. Road verge, greenways, backyard and park woody vegetation are at the center of attention for the tree care industry. Landscape architecture and urban forestry also set high demands on professional tree care. High safety standards against the dangers of tree care have helped the industry evolve. Especially felling in space-limited environments poses significant risks: the vicinity of power or telephone lines, insufficient protective gear and narrow felling zones with endangered nearby buildings, parking cars, etc.. The required equipment and experience usually transcends private means and is often considered too costly as a permanent part of the public infrastructure. In singular cases, traditional tools like handsaws may suffice, but large-scale tree care usually calls for heavy machinery like cranes, bucket trucks, harvesters, and woodchippers.
↑ Harris, Richard W., James R. Clark, and Nelda P. Matheny: Arboriculture Integrated Management of Landscape Trees, Shrubs, and Vines, third edition; Prentice-Hall, Inc. 1999.
↑ Landscape Tree Appraisal by David P. Mooter, et al.; University of Nebraska–Lincoln Extension; March 2004.
↑ Guide for Plant Appraisal, 9th ed; by the Council of Tree and Landscape Appraisers; International Society of Arboriculture; 2000.
↑ See also specific legal provisions for "tree theft" such as, for example, the Revised Code of Washington title 64.12.030 for Washington (State, USA) or similar state, provincial, or local statutes.
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