Study of Growth Function of Black Poplar (Populus Nigra) With Kermanshah and Zanjan Origin in Karaj Research Station

In order to evaluate the growth function of Populus nigra trees under homogeneous conditions, a total of 24 individuals of P. nigra (3 individuals per stand) were sampled from 8 artificial stands in Kermanshah province and 12 individuals of P. nigra (3 individuals per stand) were sampled from 4 artificial stands in Zanjan province. In order to assimilate environmental conditions, seedlings were planted under randomized complete blocks design with 3 replications in Karadj area. In growing season, height growths were measured in 6 periods and diameter growths were measured in 2 periods. The results showed no significant differences between stands in term of height and diameter growths but there were significant differences between periods in terms of height and diameter growths. In total, the results of growth parameters measuring in P. nigra stands showed the trees of the two provinces presented a fairly similar growth function during a growing season.