Silviculture and management of forest plantations (Research and Development of forestation): Comparative study of the growth form of Tectona grandis Linn. plantations planted with four different spacing at Mae-moh, Lampang [province in north of Thailand]

The study was carried out in the 13-year-old Tectona grandis Linn. plantation of Mae-Moh, Lampang. The stands were initially planted with 2x2, 3x3, 4x4 and 6x6 mxm spacing. Four random sample plots of 40x40 m2 were established in the four stands and measurements of stem diameter at breast height (DBH), total height (H), crown branching height (HB), Crown length (CL) and Crown diameter (CD) of all trees in each plot were conducted. The results revealed that for all planting spaces the correlation between diameter at breast height (DBH) and total height (H), crown branching height (HB) and crown length (CL) were hyperbolic, while the correlation between the total height (H) and crown diameter (CD) crown length (CL), crown branching height (HB) and DBH were exponential; slenderness (H/D ratio) and crown sectional area/basal area at breast (CSA/BA) decreased with increasing DBH. Total aboveground biomass and stem volume of the stand planted with 2x2 m x m spacing was found to be largest being approximately 61.54 ton/ha and 196.12m3/ha but in the 3 x 3, 4 x 4 and 6 x 6 m x m spacing stands, they were found to be next to the former one in the magnitude of above ground biomass and stem volume being 23.95 ton/ha and 37.90 m3/ha; 13.75 ton/ha and 22.80 m3ha; 2.53 ton/ha and 4.43 m3/he, respectively. Stem and branch biomass were found to be large in the order, 2 x 2 m x m x 3 m 4 x 4 m x m 6 x 6 m x m spacing. Stand density were found to be large in the order; 2 x 2 m x m 3 x 3 m x m 4 x 4 m x m 6 x 6 m x m spacing. Mean DBH were 4 x 4 m x m 3 x 3 m x m 2 x 2 m x m 6 x 6 m x m, mean total height were 2 x 2 m x m 3 x 3 m x m 4 x 4 m x m 6 x 6 m x m and mean basal area were 4 x 4 m x m 2 x 2 M x m 3 x 3 m x m 6 x 6 m x m spacing stands respectively. Mean crown branching height were found to be large in the order; 2 x 2 m x m 3 x 3 m x m 4 x 4 m x m 6 x 6 m x m, mean crown diameter were 4 x 4 m x m 3 x 3 m x m and 6 x 6 m x m 2 x 2 m x m and mean crown length were 2 x 2 m x m 3 x 3 m x m 4 x 4 m x m 6 x 6 m x m spacing stands, respectively