SITE QUALITY OF KHAYA (Khaya senegalenesis) PLANTATIONS IN SRI LANKA AS INDICATED BY HEIGHT-DIAMETER RELATION AND TOP HEIGHT TITLE

Abstract

is) being a new introduction, recommended for forest plantation establishment in the Dry and Intermediate Zones of Sri Lanka, assessment of site quality at growing localities is vital. Variables, i.e. tree height and tree diameter were measured non-destructively, at identified age classes of Khaya in Anuradhapura and Kurunegala divisions as representatives of Dry and Intermediate Zones, respectively. Khaya in Kurunegala has achieved 39.98 cm of dbh and 18.31 m of height by the age of 18-20, whereas in Anuradhapura they were 22.21 cm and 12.41 m. The dbh and tree height showed a strong degree of correlation in both divisions. Among the height-diameter models regressed, parabolic model (h = ß 0 + ß 1.d + ß 2.d2) and the model, h – 1.3 = ß 1.d + ß 2.d2 showed the best fit with the available data in Anuradhapura and Kurunegala divisions, respectively. As per height-diameter relation, site quality of the beat Polpithigama in Kurunegala is superior to the beats Ullukkulama and Rathmale in Anuradhapura, while the beat Mihintale in Anuradhapura is superior to the beats Ranawarawa and Ambanpola in the Kurunegala division. Khaya has attained average top heights of 14.2 m and 20.8 m at the base age of 18 20 years in Anuradhapura and Kurunegala divisions, respectively. Elevated top heights demonstrated the richness of site quality in Kurunegala division. Top height being the site index, it can be concluded that the beats Rathmale, Elayapattuwa and Punewa in Anuradhapura and the beats Ranawarawa and Ambanpola in Kurunegala division are inferior, while the beat Mihintale in Anuradhapura and the beats Kuliyapitiya, Nikaweratiya, Nakkawatta and Polpitigama in Kurunegala division are superior in site quality. This confirms that Khaya performs well in the Intermediate Zone than in the Dry Zone of Sri Lanka. Further, it identified the inferior sites for the growth of Khaya. These findings can direct the decision making process on future forest plantation establishment in Sri Lanka with possible refining of present recommendations. Key words: Top height, Height-diameter relation, Khaya senegalensis, Site quality