Effects of initial spacing on some allometric characteristics of 12-year-old Quercus castaneifolia plantation in central Mazandaran, Iranian Caspian forests

The effects of initial spacing layout on some allometric characteristics of 12-year-old Quercus castaneifolia trees grown in Central Mazandaran, north of Iran were examined. Trees were planted in 5 different layouts (1?1, 1.5?1.5, 2?2.5, 2?3 and 4?4 m). Tree height, diameter at breast height, natural pruning height and the survival of trees were recorded in each sample plot. Tree basal area and H/D ratio and standing volume were calculated for all trees. The results of statistical analysis showed that increasing in spacing level from 1?1 to 4?4 significantly increased the average diameter at breast height from 6.93 to 12.42 cm and survival from 53% to 85%. The average tree basal area per ha decreased from 19.98 m2ha-1 to 6.43 m2ha-1 and H/D ratio from 151 to 77 when the distance between trees increased from 1 ? 1 to 4 ? 4 m. but spacing regime had no significant effect on tree height and natural pruning height. It can be concluded that on the basis of standing volume, H/D ratio and survival rate, the best plantation spacing in this research station was 2 m ? 3 m. Statistically, about 95% of the changes in sediment yield was due to the effect of increased dry land farming area in the basin (R2= 0.95, ? < 0.05).