City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: http://read.dmtmag.com/i/36513
Tree-lined boulevard with mature Platanus acerifolia Experience has shown it takes a minimum of three prun- ing cycles (15-20 years) to redevelop a crown structure and form that is more typical for the species and deemed safe for public use and enjoyment. This emphasis is particu- larly noteworthy in that Italian cities do not seem to have comparable legal protection for Act of God tree failures afforded to states and cities in America through sovereign immunity doctrine. In Torino, a lack of constructive knowl- edge of a specific defect or predisposing condition that contributes to a sudden tree failure that causes property damage or injury is not sufficient defense in itself to protect the City from negligence claims. Like many American cities with professional urban for- estry programs, including Milwaukee, Torino follows Klaus Mattheck’s Visual Tree Assessment (VTA) protocols to assess the structural integrity of city trees in urban areas. However, unlike Milwaukee where hazardous trees conditions are effectively identified and managed through an annual windshield survey and during cycle pruning operations, Torino’s much taller and older tree population (60,000 bou- levard trees reaching 25-30 meters/82 to 98 feet) demands a very methodical and highly scientific approach. In Torino, Mattheck’s VTA protocols are strictly followed by highly qualified contractors who complete ground-based visual assessment of the crown, trunk, and root flare and utilize advanced instrumentation such as Resistograph drill- www.urban-forestry.com Thank you, Davey Resource Group, for sponsoring the 2010 Arborist Exchange. ing and sonic tomography at their discretion to fully assess the structural condition of trees with suspected defect or decay. Gianmichele arranged for a field demonstration of Resistograph and tomography structural diagnostics testing, which was fascinating. Many municipal arborists in the U.S. have observed or perform structural diagnostic testing using Resistographs; however, in the U.S., tomography is largely limited to the medical profession (e.g., in the CT scan). Sonic tomography is an advanced computerized imaging technology that is capable of detecting hidden decay and defects (cavities and cracks) in trees based on differential speed transmission of sound waves between sensors placed around the circumference of the trunk. The resulting two- 35