An arborist (or tree surgeon) is a professional in the practice of arboriculture, the management and maintenance of trees. For a topic outline on this subject see List of basic Australia topics. Townsville is a city on the north-eastern coast of Australia, in the state of Queensland. Portland is a city located in the Northwestern United States, near the Confluence of the Willamette and Columbia rivers This article is about people called professionals For the Movie, see The Professional or Leon. Arboriculture ('ɑːbərɪkʌltʃə is the cultivation of trees and shrubs A tree is a perennial Woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or Work may also include care of shrubs, vines, and other perennial woody plants. A perennial plant or perennial ( Latin per, "through" annus, "year" is a Plant that lives for more than A woody plant is any vascular Plant that has a perennial stem that is above ground and covered by a layer of thickened Bark. An arborist is distinct from a forester, or from a logger. A forester is a person who practices Forestry, the science and profession of managing forests A lumberjack or logger is a man who harvests lumber The term lumberjack is somewhat archaic having been mostly replaced by 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.
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'. ( 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. Template talkInfobox Union for usage -->The International Brotherhood of Electrical Workers (IBEW is a labor union 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. A biocoenosis (alternatively biocoenose or biocenose) termed by Karl Möbius in 1877 describes all the interacting Organisms living together In Biology, abiotic components are non-living Chemical and Physical factors in the environment. Landscape ecology is the science and art of studying and improving the relationship between spatial pattern and ecological processes on a multitude of scales and organizational levels (Wu 2006 2008 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. Parasitism is a type of symbiotic relationship between Organisms of different Species. Grazing generally describes a type of Predation in which an Herbivore feeds on Plants (such as Grasses, or more broadly on a multicellular A hazard is a situation which poses a level of threat to Life, Health, Property or environment. Introduced species|Weed Invasive species is a phrase with several definitions In Epidemiology, a vector is an Organism that does not cause Disease itself but which transmits Infection by conveying Pathogens from WEED (1390 AM) is a Radio station broadcasting a Spanish format 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 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. Aesthetics or esthetics ( also spelled æsthetics) is commonly known as the study of sensory or sensori-emotional values sometimes called 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. For other uses of the term "Pruning" see Pruning (disambiguation.
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. For other uses of the term "Pruning" see Pruning (disambiguation. Cross-cutting is an editing technique used in films to establish continuity
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. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. 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. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ 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 the trunk with an additive product called Pentrabark 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 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. Alex Shigo is widely considered the father of modern 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. For other uses see Quarantine (disambiguation Quarantine is voluntary or compulsory isolation typically to contain the spread of something
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. In tort law, a duty of care is a legal obligation imposed on an individual requiring that they adhere to a reasonable Standard of care while performing any acts  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. Vandalism is the behaviour attributed to the Vandals in respect of Culture: ruthless Destruction or spoiling of anything beautiful or Venerable  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. A Tree Preservation Order or TPO is a part of Town and country planning in the United Kingdom. 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. A homeowners' association (abbrev HOA) may be A legal entity created by a real estate developer for the purpose of developing managing and selling a community A real covenant is a Legal obligation imposed in a Deed by the seller upon the buyer of Real estate to do or not to do something  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. Dendrochronology (from Greek grc δένδρον dendron, "tree" grc χρόνος khronos, "time" and grc -λογία 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. An expert witness is a Witness, who by virtue of Education, Training, Skill, or Experience, is believed to have Knowledge 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. 
Other significant study materials and references for arborists include:
Some noteworthy arborists include: