Growth performance and carbon accumulation of Khaya ( Khaya senegalensis) in Sri Lanka

Abstract

Khaya (Khaya senegalensis) being a new forest plantation species, its growth performance under Sri Lankan conditions has not been evaluated. Further, carbon sequestration by forest plantations, which forms an important option in climate change mitigation, has not gained much attention in Sri Lanka. Hence, the present study aimed at assessing the growth performance and carbon accumulation of Khaya plantations in Sri Lanka. The tree height and tree diameter were measured non-destructively in identified age classes and biomass was estimated with allometric equations. Khaya in Kurunegala division (Intermediate Zone) has achieved 39.98 cm and 18.31 m of dbh and height, respectively, by the age of 18-20 years, whereas in Anuradhapura division (Dry Zone) it was 22.21 cm and 12.41 m, respectively. Significantly higher dbh and tree height (p<0.05) indicates the better site conditions in the Kurunegala division for superior growth of Khaya compared to those in the Anuradhapura division. The dbh and tree height of Khaya showed a strong correlation in both divisions. Significantly higher (p<0.05) biomass of Khaya was recorded in Kurunegala than in Anuradhapura division. The average carbon sequestration of K. senegalensis was 88.98 and 127.92 t/ha in Anuradhapura and Kurunegala divisions, respectively. Khaya plantations in Anuradhapura division (741.92 ha) and Kurunegala division (475.20 ha) have accumulated 21,785 t and 27,969 t of carbon, respectively. Growth performances evaluated in the present study can guide the future decision making process in establishment of forest plantations in Sri Lanka. Regional baseline carbon estimates of Khaya generated by this study could effectively be utilized for carbon budgeting programmes until validated further by increasing the frequency of measurements of variables and developing allometric relationships specific for K. senegalensis.