Abstract
This work was put to determine the best value of specific gravity of Poplar nigra through different sampling criteria. Four groups of seven years old poplar trees were used (3, 5, 7 and 12 trees). Samples were taken at different heights from the stem of each tree(at :stump height , Breast height , at each one meter and two meters along the stem )in addition other samples were taken from fixed position (at: Breast height ,1/2 and 2/3 the height of tree) to determine the specific gravity . The results showed , a significant variation among the groups of trees and throughout the stem height .It is found that the groups of 3 and 5 trees gave values of specific gravity not representative to the actual values ,The same is true for the average values at breast height and for the three levels of height in the stem ,because it appeared that the first gave average value was lower and the second level gave higher average than the actual value of the specific gravity of poplar trees, while the average values at stump height in the group of 12 trees gave a considerable value which is close enough to the actual value ,and one can use it as a representative value of the specific gravity of Poplar nigra.
