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' · another measure used Io approxirno~e ~ ~.~ ~
<br />..'a,ree3PRZ, iJthedis,oncefromthe i~.,..~Ahead!
<br />',, tree trunk equal to 40 percent of the -'
<br />~ree'~ hel~hL This method is more
<br />'appropriate where branch .. You'll save time and money J[ you
<br />~'~pread is narrow, develop a landscape protection plan
<br />:; '" ' ~' ~ .... before construction begins. Careful
<br />
<br /> ..... ~' ' . expense and heartache of later repair-
<br />
<br /> ..: .. ~' to construction activities.
<br /> , : hek~ht These steps will help you create a
<br />
<br /> :" height x 0.4
<br /> :.... - ,= criticalro0~ radius
<br />
<br /> · , Protected
<br />
<br />:: '5.' U~'ff0rt-p, nat~ly,.'°n most sites space
<br />is limited and this rUle must be bent.'."
<br />]u§t..how. dose ar{ activity can come
<br />~4th0ut, serlo_usly threatening the ·
<br />survival.., of a tree depends upon the '"
<br />species, the extent of damage, and. th~ '
<br />piam's health. Some'healthy trees can
<br />su,wiV~ after losing 50 percent of their
<br />roots. Ho0eever, other species are
<br />extremel? sensitive to root cutting,
<br />even outside the, dripline.
<br /> ' Table 1 shows ~:he relative sensi:, .
<br />tivity of various tree species to root .~ '-'
<br />distur, bance., I{ possible, disturb no. ·
<br />more than 25 percent o£ the roots
<br />wJthinthe dripline for an), tree, · ' ....
<br />?0tect intermediate species to the
<br />dripline, and allow extra space b'eyond
<br />.',he dripLine for sensitive species. For,
<br />all frees; avoid needless or excessive
<br />5amage..- A, qualified tree-care spe-
<br />dalist can.help you determine how..'
<br />much root intefferenke a particul,ar7 :
<br />tree can tolerate. ' .'
<br /> ' ? When dealing .wi. th trees that have
<br />been growing Jn the'forest or that
<br />
<br />'naturally have ~ narrow growth habit,
<br />an approach called the "critical root .
<br />radius" is more accurate than the
<br />dripline method for determining the
<br />PP..Z. This is particularly true for
<br />c61umnar trees and for those where
<br />Competition has reduced the canopy
<br />spread. ..
<br /> To calculate critical root radius,
<br />estimate the tree's height and multiply
<br />by.40 percent (0.40). The result is the
<br />approximate distance from the tree
<br />trunk in which a critical amount of the
<br />tree's roots may be .found. Whenever
<br />possible, isolate this area from con-
<br />'struction disturbance and treat it as
<br />the' PRZ (Fighi-e 2).
<br />
<br /> I. Mark construction zone
<br /> boundaries..
<br />
<br /> Obtain a complete set of site
<br /> deve}opment plans, including the
<br /> proposed location of buildings,
<br /> driveways, sidewalks, and utility
<br />· lines. Ask the builder or architect to
<br /> mark areas wher~ heav, y equipment
<br /> will be used, where soil will be
<br /> permanently added or removed and
<br /> what depth, and where fill and '
<br /> building materials will be temporarily
<br /> stockpiled. Use a measuring tape,
<br /> stakes, and string to temporarily mark
<br /> ti~e boundaries of construction activi-
<br /> 'ties on the Site.
<br />
<br /> '2. Inventory trees.
<br /> on the site.
<br /> Reco~d the location, size, and
<br /> health, oi~ each tree. Wilted leaves,
<br /> broken or dead limbs, trhnk rot, and
<br /> thin tops are all signs of stress. Trees
<br /> that are overmature, display poor
<br /> form, lean heavily over future build-
<br /> ings, oi' have severe insect or disease
<br /> problems (Figure 3) should be marked
<br /> for removal 'prior to construction.
<br /> Also mark trees that need pruning to
<br /> make room'for future structures and
<br /> construction equip.ment.
<br />
<br /> 3. Select the trees
<br /> to be saved.
<br />
<br /> 'Examine the site carefully and
<br /> note how each tree fits into the future
<br /> -landscape. Keep in mind that the
<br /> builder may be able to shift the
<br /> location of a building, utility line, or
<br />
<br />
<br />
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