Estimation of carbon sequestration potential in coconut plantations under different agro-ecological regions and land suitability classes

Abstract

The study estimated the carbon sequestration potential of 25 year old Tall x Tall coconut (Cocos nucifera L. variety
typica) plantations under S2 (highly suitable for coconut) and S4 (moderately suitable for coconut) soils in wet (WL 3
, high moisture availability), intermediate (IL 1a, moderate moisture
availability) and dry (DL3, low moisture availability) agro-climatic conditions during May to September 2009. Variation in total carbon stock (plant and soil), total carbon input (measured as Gross Primary Production of coconut, GPP), total carbon output (measured as plant and soil respiration) and net carbon balance of ecosystems were assessed. Eight coconut palms and sample plotsper site were used for estimations (two factor factorial with eight replicates). There is a significant agro-ecological region (AER) x land suitability class (LSC) effect on all the components of the carbon balance in a coconut plantation. The total ecosystem carbon stock (Btot–eco ) reduces along a decreasing moisture gradient from WL3 to DL3 and decreasing soil fertility gradient from S2 to S4. The GPP and Rtot–eco do not show a reduction along a decreasing moisture gradient from WL3 to DL3 on S2, whilst it shows a reduction from WL3 to DL3 on S4 . The net C balance reduces from WL3 to DL3 on S4 , whilst it does not reduce from WL3 to DL3 on S2. C stock of the ecosystem varied between 32 and 72 Mg Cha-1 whilst the net carbon balance varied between 0.4 and 1.9 Mg C ha-1 month-1 under different growth conditions. Of the measured components, GPP and maintenance respiration ofcoconut palms and soil respiration had greater contributions to the overall C balance of the system. This is the first report oncarbon sequestration potential in coconut plantations of Sri Lanka.