Thining of sprout groups for optimal number to raise Poplar clones production.

Pruning and cutting some of the sprouts of poplar clones in short rotation system causes the left sprouts use more minerals, light, water and at last they have thicker and taller trunks which can be used in wood industries like paper industry. This project wants to study the effects of pruning in wood production as well as dimensions of wood products. In the project ٥; clones were used: Populus x euramericana costanzo, Populus x euramericana 561,41 Populus x euramericana vernirubensis, Populus x euramericana triplo ﻭ Populus x deltoids 63,8 The project was done in 5000 square meters with statistical split plat design with 3 replications and ٥; main treatments (clones) and ٣ sub treatments (numbers of the shoots in each stool) in 4 time periods (2004 to 2006) in Karaj Alborz research station. The parameters like diameter (dbh) and height of the shoots were measured at the end of every growing season and by using diameter the basal area was calculated. At the end of the period the wet and dry weight of biomass was measured and after calculating the averages of the parameters such as diameter, height and dry biomass were analyzed by using SAS software. The results showed that the average of the shoots in the third treatment (control treatment) ranged from 3 in the P.d. 63,8 to 5,8 in P.e. 561,41 in each stool. The clones P.d. 63,8 and P.e. 561,41 were taller and thicker in comparison to other clones. The average of diameter and height of clones in the first treatment (one shoot in a stool) were more than the second treatment (two shoots in a stool) and also the parameters in the second treatment were more than the third treatment (several shoots in a stool). The most average dbh was 8cm for P.d. 63,8 in the first treatment and the least was 2,6 cm for P.e.vernirubensis clones in the third treatment. The clone P.d. 63,8 with the 9,14m height average in the first treatment was the tallest and P.e. 561,41 with the 4,24m height average in the third treatment was the shortest. Significant differences were observed in the average height and diameter of the clones in different treatments. Mean basal area -which is a suitable trait for estimating of clones biomass productionin the third treatment was more then the second and the first treatments, in the contrast of diameter and height. Produced biomass of P.d. 63,8 and P.e. 561,41 were the most and for P.e.vernirubensis it was the least and significant clonal differences were observed between the mean of this parameter. Biomass production in 4 P.euramericana clones in the third treatment was more then the first and second treatments. But in P.deltiodes clone the produed biomass in the first treatment was more then the second and the third treatments Dry biomass ranged from 9,118 ThÏ1 yÏ1 for P.e.vernirubensis to 19,285 ThÏ1 yÏ1 for P.d. 63,8 to in the first treatment.