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12/02/97 13:55 $541 683 6826 EUG PUBLIC WORKS -4-4 MAINTENANCE 0001 /003 <br /> Post -Ir brand fax transmittal memo 7671 I x of pages ■ . �7 , / ' v �� j <br /> To n r Y a rh sty i ±F►om .P.s r6 (� [!�r <br /> Co. Co. <br /> Dept. Phone */ <br /> 439'S 1st St <br /> Fax# Fax M Cottage Grove, OR 97424 <br /> November 25, 1997 <br /> Ms. Christine Andersen, Director <br /> Public Works Dept. <br /> 858 Pearl St. <br /> Eugene, OR 97401 <br /> Dear Ms. Andersen, <br /> I am writing to express my thanks for the opportunity to have been involved <br /> with ad hoc committee on the Hendricks trees issue. I know this wasn't the <br /> practiced way,of doing things for the city: and it took quite a stretch to open for <br /> some'form of citi.zeninvolvenient.. I realize many issues :remain to be addressed <br /> and I encourage you to continue to iiivolve° intetested citizens, in this and Other <br /> projects. I suggest citizen involvement early in the process. <br /> I. wanted to express my ongoing concern with the hazard tree: issue at <br /> Hendricks Park. I have had three interactions with Public Works personnel since <br /> the meeting of Oct. 27th, and am concerned there was little connection made with <br /> Tim Brown of Frontier Tree Service of Bellevue, Washington. Tim will be in <br /> Eugene to work another week on a BLM contract some time. in January 1998. I <br /> plan to be in the field with him for at least a day. Perhaps this would provide an <br /> opportunity for one of the 'staff at urban forestry to accompany me. <br /> In reference to the tree /stand stability issue, :I have had the opportunity to <br /> contact Stephen J. Mitchell, .professor of silviculture at the University, of British <br /> Colombia, who has expertise with windthrow/windfirmness in Douglas fir stands <br /> and has published a number of papers in this field. Professor Mitchell indicated <br /> there is a stocking (density) threshold in which removing more trees would greatly <br /> increase the windthrow hazard. The' threshold varies with stand aspect, height, <br /> age, prevailing wind: direction for both endemic and catastrophic winds, structure, <br /> even-aged or uneven -aged condition, health & vigor. Professor Mitchell <br /> _- - - einpl3asi sl t as . extremely -ur por.:.tant -. look: at- each,situation - from - -a- stand - -._ _ ...: - -- <br /> level and individual tree level. In otherwords, the removal of individual trees may <br /> have a significant effect on the stability of the stand if the removal crosses the <br /> threshold for stand stability. <br /> Professor Mitchell said if we examine crown position of each tree, the <br /> dominants of the crown layer tend to be the most windfirm The intermediates <br /> and suppressed tend to be the next most windfirm due to the :lack ' crown and <br /> height. The codominants are the least windfirm as they have created the greatest <br /> competition for themselves putting all growth into height, protected by the <br /> adjacent trees from the wind. Most of the 19. trees selected for removal are in <br /> this codominant class. The more open grown the tree, the more time it has had to <br /> adapt to the effects of wind.. Windfirmness is a function of wind exposure over <br /> time. Professor Mitchell said trees : could adapt to an increasing exposure to wind, <br />