Abstract
Many mathematical function were used to estimate tapering degree of Populus nigra main stem tree in Zakho . 35 sample obtained thought stand classification and according to there density using strata randomized sampling method . Each sample area was 0.01 hectare .To record all changes that affect longitudinal and diametrical growth , one tree was chosen from each sample area , and all tree morphological dimension were recorded , in addition to distance between the trees . The chosen trees were felled and cuted into different parts at one meter length from ground level to 4 cm stem diameter . By using simple linear regression , four mathematical Models were established. In order to find the best fit model for these four Models , coefficient of determination, standard error of estimate were used and the following model give the best result
d0 = b0+b1 cw (b2 (-b3hi) )
R2=0.87 S.E%=0.6369
By using above model , tapering tables was prepared for Populus nigra trees grown in Zakho at different stand density . By using this table a desired management decision can be chosen which can be suitable for the harvesting plan.
