220 Labrosse et al.: Effects of Tree Stabilization Systems on Tree Health ment resulted in development of trees with significantly more taper. Stem taper remained the greatest on these trees even af- ter stabilization systems were removed, demonstrating the im- portance of trunk movement for adequate taper development. Appleton (2006) evaluated the response of red maples (Acer rubrum ‘Red Sunset’) to ten different TSS approaches. The study included a control with no TSS, six aboveground methods, two belowground methods, and one combination below and aboveground method. Markings and damage from the TSSs were observed on tree trunks two years after trans- plant on trees using aboveground methods. The change in caliper dimension over a one-year period was significantly different among different TSS methods. The least amount of caliper growth was found on a belowground product and the combination, while the greatest growth in caliper was found to be with an aboveground guying method. The study con- cluded that the different TSS products had little effect on total growth of trees but the longer trees were stabilized, the more serious negative effects on tree health could be observed, em- phasizing the importance of removing these systems as soon as the tree’s root system is established (Appleton 2006). Research suggests that TSSs are not necessary in ev- ery planting situation. In some cases, TSSs may injure the tree and interfere with growth and development (Harris and Bassuk 1993; Appleton et al. 2008; Eckstein and Gil- man 2008; Alvey et al. 2009). Negative effects of TSSs are reduced taper development, increased height growth, de- creased caliper growth, trunk deformities, and undesirable water stress responses (Appleton et al. 2008). Multiple stud- ies of TSSs have arrived at similar conclusions with regard to the effects of TSSs on tree development: Jacobs (1954), Harris and Hamilton (1969), Leiser et al. (1972), Wrigley and Smith (1978), Harris (1984), and Patch (1987) have all shown that staking equipment increases tree height, while taper development and caliper growth are decreased. TSSs can cause changes in development because of a lack of movement in the canopy and trunk, which is necessary for proper taper development (Harris and Hamilton 1969). A TSS can cause morphological injury to trees in addi- tion to causing physiological and developmental chan- ges (Costello et al. 2003). The TSS hardware can girdle trunks, which can then lead to a number of stress-related symptoms. Girdling can impair health, stunt growth, and possibly lead to tree death (Gilman 1997; Johnson 1997; Costello et al. 2003). If the TSS equipment remains on the tree too long then tree vigor may also decline, predis- posing the tree to infection (Clark and Matheny 1991). Researchers agree that in certain instances, transplanted trees may need a stabilization system. These instances in- clude trees with a dense canopy, are located in windy sites, or have poor soil stability (Harris and Hamilton 1969; Apple- ton et al. 2008). General prescriptions for TSSs should be carefully considered for their effects on tree growth and de- velopment (Harris and Bassuk 1993; Appleton et al. 2008). Landscape architects and urban foresters who specify tree planting must ensure the best care and health of the trees as they adjust to their new location. This research aimed to uncover the health effects associated with the use of tree stabilization systems with an observational study based on the literature on TSS effects. Results may help to under- ©2011 International Society of Arboriculture stand TSS effects in different settings and lead to more well-informed establishment of healthy urban forests. This paper investigates the effects of tree stabil- ization systems on tree health to improve urban for- est planting specifications. The research objectives are: 1. Measure the effects of TSSs on trees through evidence of symptoms 2. Understand the effects of TSSs on tree health—both posi- tive and negative—from literature and analysis of observed symptoms 3. Assess if TSS type or cultural factors change the suscepti- bility of trees to TSS effects METHODS . Guelph is located in USDA Hardiness Zone 5a with soils that are dominated by well-drained, slightly basic loams. Tree Sample The study authors randomly selected 488 trees from both pub- lic land and recently developed, private land in Guelph, ON. Public sites included parks, stormwater management areas, and public open spaces (five public sites). These trees were recently (2007–2008) planted by private contractors and remained un- der warranty at the time of study. If specified, the TSS would likely still be in place on these trees. Private sites were gener- ated from a list of site development plans approved by the City of Guelph between 2002 and 2007 and included commercial, residential, industrial, and institutional land uses. Sites within each privately owned land use category were randomly select- ed to include an equal distribution of sites within each category (20 private sites). No information was available for how long a TSS was on the sampled trees, so the date of city site plan ap- proval is an approximate measure of the time since planting. Data Collection The trees were observed between October 17 and 22, 2009, and information was recorded about the location of the trees, their species, size, the types of TSS used, and any visible health condi- tions. Tree locations were recorded along with the species to con- sider any patterns that may make a tree more or less susceptible to the effects of TSSs. Trees were chosen to be visibly representative of site conditions and planting locations. The presence of TSSs was noted along with the materials and method used to stabilize the tree. The diameter at breast height (DBH) was recorded using a handheld caliper. Health defects associated with TSS were cat- TSS were cat- egorized under headings of overall health (signs of necrosis or death), crown dieback, girdled trunk, pests or disease (nonspe- cific), pinched or swollen appearance above the point of constric- tion, leaf scorch, wilting, stunted growth, flagging, and epicormic sprouting or excessive suckering below the point of constriction (Johnson 1997; Costello et al. 2003). Each symptom was record-Each symptom was record- ed on a scale of one to five, with one indicating severe health problems and five indicating the tree was in good health (Table 1). Urban trees within the City of Guelph provided the basis for in- vestigating the effects of TSSs on tree health. This city is of a representative size and population to other cities in Southwestern Ontario, Canada, and has a population of 118,000 and land area of 86.7 km2
September 2011
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