Characteristics of Gaseous Carbon Emission from a Tropical Peatland Fire: A Plot-Scale Field Experiment in Central Kalimantan, Indonesia

Abstract:

Tropical peatland in Southeast Asia is a vast reservoir of terrestrial carbon, which covers 24.8 million hectares and stores 68.5 PgC peat, equal to 11–14% of global peat carbon. In recent decades, large scale peatland fire has occurred frequently in that region, in which many areas of peatland were reclaimed with intention to use the land for forest plantation and rice paddy. We conducted a plot-scale peat burning experiment to elucidate the characteristics of gaseous carbon emission from a tropical peatland fire at the ground level.

The experimental site was established at an open area 20 km southeast from Palangka Raya, Central Kalimantan Province, Indonesia. The size of the burning plot is 4 m in length and 3 m in width. Gas samples were collected at heights of 1.0, 0.5, 0.0 (aboveground), −0.1 and −0.2 m (belowground) through stainless steel and/or aluminum tubes settled across the edge of the plot. The concentrations of carbon dioxide (CO₂), carbon monoxide (CO), methane (CH₄) and particulate matter (PM) was determined. Soil temperature was recorded every 10 minutes 0.1 and 0.2 m below the ground surface. Twelve iron rods were installed in 1-m by 1-m square grid to determine the depth of burn scar.

After ignition, flaming stage of peat burning was ceased within 1-2 hours. The following smoldering stage continued for a week. In the flaming stage, soil temperature at −0.1 m increased tentatively. After the smoldering stage began, the temperature rapidly increased to 350–450°C. Response of soil temperature at −0.2 m was less prominent. Concentrations of gaseous components became maximal in the flaming stage. During the smoldering stage, the concentrations gradually decreased. The influence of burning on CO₂ and PM was prominently remained at −0.1 m, whereas those at −0.2 m were not so much. The averaged burnt depth was 5.8±5.1 cm. Based on bulk density of 0.22 g/cm³ and carbon content of 55.5%, the amount of carbon lost from the plot was 85.3 kg. Most of the gaseous carbon was evolved as CO₂. The second major emission form was CO, which increased from 7% in the flaming stage to about 20% in the smoldering stage. The proportions of CH₄ and PM were consistently small.