Abstract:
ABSTRACT
Carbon sequestration by tree is imperative in tumbling atmospheric carbon dioxide level. Hence, forest plantations are
considered highly efficient systems for carbon sequestration, which plays a vital role in climate change mitigation. While,
carbon sequestrations of forest plantations were little focused in Sri Lankan context, present study aims to validate its potential,
using Khaya plantations in Anuradhapura and Kurunegala divisions of Sri Lanka. Variables, i.e. tree height and tree diameter
were measured non-destructively at identified age classes to estimate biomass using allometric equations. DL1b being the sole
agro ecological region in Anuradhapura, resulted less variation in biomass distribution through age classes, whereas it was
irregular in Kurunegala, visualizing the climate variation of the different agro ecological regions (DL1b, IL3, IL1a, IM3b) within
the division. Greater biomass of Khaya recorded in Kurunegala was attributed to moisture rich growing conditions, whereas
lower biomass in Anuradhapura resulted with less annual rainfall and prolonged drought, indicating the strong association of
biomass with environmental stress. Greater root:shoot ratio (R/S) of Khaya was observed in Anuradhapuara, while R/S had
decreased through age classes in both divisions. The average above ground carbon sequestration of Khaya i.e. 88.98 and 127.92
tonnes per ha in Anuradhapura and Kurunegala divisions were well ahead of the IPCC’s benchmark of plantation forests in
‘Tropical Dry’ climate i.e. 30 tonnes per ha, indicating its potential of climate change mitigation, besides the timber use. The
total amount of carbon sequestered by existing Khaya plantations amounted to 21,785.25 and 27,969.10 tonnes in Anuradhapura
(741.92 ha) and Kurunegala (475.20 ha) divisions, respectively. Despite the greater extent, Khaya in Anuradhapura assimilated
less carbon due to stressful conditions imposed by climate and being in younger age classes. While, carbon estimates enable
economic valuation of forest plantations in the context of carbon crediting, the regional baseline carbon estimates of Khaya
generated by present study can be effectively utilized for carbon budgeting programmes, until further validated with
comprehensive survey of individual trees and by developing allometric relationships specific for Khaya senegalansis.
Key words: Khaya senegalensis, Carbon sequestration, Climate change mitigation, Biomass, Age classes
