عنوان مقاله [English]
The trial was conducted in 1995, under statistical method of split plots and Fully Randomized Design, with three replicates. The main treatments consisted of three levels of thinning (control, medium and heavy) and the secondary treatments consisted of two thinning intervals (three and five years). Three plots (0.3- 0.4 ha) were allocated at each replicate of a Maple plantation stand in Emamzadeh-Abdullah experimental site (Caspian Forests of Iran). Each plot was divided to two subplots. Before beginning thinning in the ten-year old stand in 1995, height was measured in the plots which average mean and dominant height were 10.86 and 12.14m., respectively. The qualitative characteristics of the future trees were measured annually, where the whole trees at each subplot were measured in accordance to their thinning intervals. Overall, 307 individual trees were selected in the nine plots as future trees.
The results show that the effects of thinning treatments, particularly the heavy level on growth parameters were significant. The effects of heavy thinning on future trees diameter growth rate (1.3 cm/y at D.B.H), crown diameter and slenderness factor was significantly more than the control thinning in 2002. Thinning increased the mean stem diameter from 12.7 cm in 1995 to 18.5 cm in 2001. As a result the wood quality potential increased for different products. The heavy thinning doubled mean basal area after three years (1995-1998) from 12.73 to 24.54 m2/ha (3.0 m2/ha/y). At the same period, mean volume growth for the remained and the whole trees (removed+remained) were 15.43 and 29.07 m3/ha/y, respectively.