Arboriculture & Urban Forestry 35(3): May 2009 Arboriculture & Urban Forestry 2009. 35(3): 157–164 157 Efficacy of Conventional Tree Stabilization Systems and their Effect on Short-Term Tree Development Alexis A. Alvey, P. Eric Wiseman, and Brian Kane Abstract. We evaluated three conventional tree stabilization systems (staking, guying, and root ball anchoring) on 6.4 cm (2.5 in) caliper field-grown, balled and burlapped white ash (Fraxinus americana L. ‘Autumn Purple’). At five weeks and at seven months after planting, performance of the stabilization systems was evaluated under ambient wind conditions as well as wind-simulating pull tests. Nonstabilized ash trees remained upright during both the 5-week and 7-month studies de- spite occasionally substantial wind gusts. From the pull tests, the study found the stabilization systems performed equally well and that even nonstabilized ash trees were tolerant of moderate to heavy wind loads. Stabilization systems differed in the maximum force they endured before component failure. The guying system withstood forces 1.7 to 2.5 times greater than the root ball anchoring and staking systems, respectively. Stabilization system components were very durable during the first growing season and did not substantially impact tree height growth, shoot elongation, root diameter, root length, or root mass seven months after planting. After one growing season, both nonstabilized and previously stabilized trees remained up- right until unrealistically large loads were applied. Practical implications for landscape tree management are discussed. Key Words. Anchoring; Guying; Planting; Pull Tests; Staking; Tree Stabilization; Tree Support; Wind. Tree stabilization systems (TSS) are commonly installed on transplanted trees to provide (1) anchorage and aid root estab- lishment, (2) trunk support for trees that cannot stand upright on their own, and (3) protection from landscaping equipment, au- tomobiles, and vandals (Leiser and Kemper 1968; Harris 1984; Smiley et al. 2003; Appleton et al. 2008). The first application is the most common; recently transplanted landscape trees may be prone to destabilization from root ball shifting and inad- equate root anchorage, which can require costly follow-up care to reposition or replace the tree (Appleton et al. 2008). It is be- lieved that excessive movement of the root system breaks new roots that have extended into the backfill soil, possibly inhibit- ing tree establishment and growth (Appleton and Beatty 2004). There are three conventional TSS configurations: staking, guy- ing, and root ball anchoring. Staking entails one to four tall stakes (one-third to two-third total tree height) positioned around the tree with a horizontally-oriented strap secured between the top of each stake and the trunk. Guying entails one to four short soil anchors positioned around the tree with an angled guyline secured between each anchor and the trunk. Root ball anchoring entails immobiliz- ing the root ball with stakes and/or straps placed over, around, or through the root ball and beneath the soil surface. These TSS con- figurations can be fabricated from general hardware supplies or purchased as proprietary systems. A recent survey identified no less than a dozen commercial TSS products (Appleton et al. 2008). While there are compelling reasons to use TSS on landscape trees, there are also numerous disadvantages of tree stabilization (e.g., Appleton et al. 2008). Of greatest concern to arborists are the cost of TSS and their potentially negative impact on tree health and development. The costs to purchase, install, and maintain a TSS can add considerably to the total establishment cost of a landscape tree. In a recent survey of 250 landscape practitioners, cost and ease of removal ranked highly among the most important short- term and long-term TSS selection criteria (Appleton et al. 2008). TSS components that attach to trunks or branches can cause abrasion and girdling (Leiser and Kemper 1968; Harris and Ham- ilton 1969). In Boston, MA, U.S. staking caused more damage to trees than automobiles or vandalism (Foster and Blaine 1978). Nearly three-fourths of surveyed practitioners had observed tree damage (usually trunk girdling) from TSS not removed in a time- ly manner (Appleton et al. 2008). Aboveground TSS can also pre- dispose trees to trunk breakage (Leiser and Kemper 1973); staked trees have been observed with their trunks broken at the point of attachment (Patch 1987). Leiser and Kemper (1968) estimated that stakes attached above two-thirds of the total tree height caused trunk stress three to five times greater than on nonstaked trees. Aboveground TSS can also alter trunk and root development, which may have implications for long-term structural integrity. Holbrook and Putz (1989) found that four-year-old sweetgum (Liquidambar styraciflua L.) saplings that had been guyed for two years were taller and had thinner, less-tapered stems than nonsta- bilized saplings. Neel (1967) applied various staking configura- tions to one-year-old, containerized sweetgum, Japanese zelkova (Zelkova serrata Thunb.), mountain birch (Betula pubescens Ehrh.), and Chinese pistache (Pistacia chinensis Bunge.). Staking decreased the rate of diameter growth, increased height growth, inhibited the formation of reaction wood, and decreased trunk ta- per progressively as the degree of tree immobilization increased. After guying young Scots pine (Pinus sylvestris L.) for two years, Fayle (1976) found that roots originating from the trunk-root junction of guyed trees had grown in width only about half that of nonstabilized trees. Fayle also found that compression wood was present more frequently and in greater quantities on the exposed, horizontal roots of nonstabilized ©2009 International Society of Arboriculture
May 2009
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