Site index and yield of teak plantations in Lampang province [Thailand]

Study of site index and yield of teak plantations was carried out at Lampang province in 1983-84. The 82 sample plots each of 40 x 40 sq.meter. were laid out in 10-42 year old plantations. Diameter at breast height and total height and total height of teak in plots were measured and recorded. The relationship between age and average height of each plot was set up and a curve was drawn by site index. Using the height at base age (30 years) as a medium site, site index curves were classified into 5 site qualities; 10,15,20,25 and 30 meters. The best site qualities (site index 30) were Huay-Prao and Mae-Sai-Kum plantations at 10 years and Huay-Tak plantation at 40 years. From the recorded data, the relationships of stem volume and average diameter at breast height were expressed as regression equations. Stem volume per tree of teak plantations could be estimated by the following equations : site index 10: Vs = 0.00011(D)2.66054 (r=0.9911), site index 15: Vs = 0.00036(D)2.15012 (r=0.9788), site index 20: Vs = 0.00094(D)1.85258 (r=0.7861), site index 25: Vs = 0.00019(D)2.45599 (r=0.9885), site index 30: Vs = 0.00017(D)2.51308 (r=0.9834) where Vs = stem volume (outer bark) (cubic meter./ha.), D = average diameter at breast height (cm.). The relationship of yield, basal area, number of trees per unit area and average diameter at breast height on age and height could be expressed by the following equations : Vs = -73.04435 - 0.08039 Age + 10.72483 Ht(r = 0.465), BA = -2.00352 - 0.00953 Age + 0.82028 Ht(r = 0.8767), D = 0.42371 + 0.18850 Age + 0.81749 Ht(r = 0.9253), In No = 6.60743 - 0.03199 (D) (r = 0.4923), Where Vs = Stem volume (outer bark) (cubic meter./ha.), BA = basal area (sq.meter./ha.), D = average diameter at breast height (cm.), No = number of trees (tr./ha.)