Estimating the Relative Contributions of Root Respiration and Peat Decomposition to the Total CO2 Flux from Peat Soil at an Oil Palm Plantation in Sumatra, Indonesia

The decomposition of organic matter influences CO2 flux in peat soils. However, determination of the flux from the decomposition process is usually over-estimated because the total CO2 flux calculation includes root respiration. We clarified this issue addressing the following aims: (i) to study the relation of oil palm root distribution in peat soils to the flux and (ii) to estimate the relative contribution of root respiration and peat decomposition to the total CO2 flux. The study was conducted between January and June 2012. In the research area, three transects were established perpendicular to drainage channels, where nine14-year-old oil palm trees were selected and used as observation sites. Eight closed chambers were established as observation points at each site. We measured CO2 flux at each point using an Infra Red Gas Analyzer (IRGA). Root and peat samples were collected from each observation point to measure root density and analyze peat chemical properties. Our results showed that the pHH2O and nutrient content of P, K, Ca and Mg in the peat soils significantly increased of CO2 flux. Oil palm roots at depths of 0–15 and 15–30 cm nearest the tree showed the highest density, while root densities gradually decreased with increasing distance from the tree. CO2 flux in the peat soils nearest to the tree were highest at 0.44 ± 0.23 mg CO2 m-2 sec-1 (or 137.7 ± 73.4 t CO2 ha-1 yr -1). CO2 flux significantly decreased with increasing distance from the tree, showing the lowest value of 0.10 ± 0.04 mg CO2 m-2 sec-1 (or 30.67 ± 12.4 t CO2 ha-1 yr -1). We conclude that the CO2 flux was derived from peat decomposition and root respiration. Using the integral equation approach, the relative contribution of root respiration and peat decomposition was 74 and 26%, respectively to the total CO2 flux.