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Arborlst or designee, Duration of tree maintenance services could be <br />less than one full work day, requiring Contractor to mobilize to another <br />work area, Most assignments will require several job site set ups to <br />perform the work dependent on field conditions. A Service Request <br />Prune typically consists of one or more of the following pruning <br />treatments found in sections a„ b, c., d., e. and f below: <br />a. Structural Prune: Structural Pruning Is the removal of live <br />branches and stems to Influence the orientation, spacing, growth <br />rate, strength of attachment, and ultimate size of branches and <br />stems. Structural pruning is used on young and medium -aged <br />trees to help engineer a sustainable trunk and branch <br />arrangement. If young trees are pruned to promote good <br />structure, they likely will remain serviceable in the landscape for <br />more years than trees that have not been structurally pruned. <br />This pruning type can be summed up In the phrase: subordinate <br />or remove codominant stems. Small- maturing trees and shrubs <br />are structurally pruned to properly space codominant stems, <br />reduce or remove rubbing limbs, and provide desirable crown <br />configuration. All branches are to be kept less than half the trunk <br />diameter, Spacing scaffold limbs allows for the trunk and leader <br />to develop properly, gives the canopy a mare balanged form,, and <br />b. Crown Cleaning: Crown Cleaning or cleaning out is the removal <br />of dead, diseased, crowded, weakly attached and low -vigor <br />branches and water sprouts from the entirety of the tree crown. <br />Cleaning Is the selective removal of dead, diseased, detached, <br />and broken branches. This type of pruning is done to reduce the <br />risk of branches falling from the tree and to reduce the <br />movement of decay, insects, and diseases from dead or dying <br />branches into the rest of the tree. It can be performed on trees of <br />any age but is most common on medium -aged and mature trees. <br />Cleaning Is the preferred pruning type for mature trees because <br />it does not remove live branches unnecessarily. Cleaning <br />removes branches with cracks that may fail when the interior <br />wood dries, <br />C. Crown Thinning: Crown Thinning includes the selective removal <br />of branches to Increase light penetration and air movernent into <br />and through the crown. Increased light and air stimulates and <br />maintains interior foliage, which in turn improves branch taper <br />and strength. Thinning reduces the wind -sail effect of the crown <br />and the weight of heavy limbs. Care must be used to avoid <br />stripping branches of all foliage at the interior of the tree crown. <br />This practice, known as "lien tailing" disrupts the structural <br />Integrity of the tree, making it subject to limb and branch failure, <br />especially during high winds. Thinning the crown can emphasize <br />the structural beauty of trunk and branches as well as improve <br />the growth of plants beneath the tree by increasing light <br />penetration. When thinning the crown of mature trees, up to 25% <br />of the live foliage may be removed unless directed otherwise by <br />the City Arborist. <br />25B -27 <br />