Abstract:
stration 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
