Late Holocene ENSO-related fire impact on vegetation, nutrient status and carbon accumulation of peatlands in Jambi, Sumatra, Indonesia

Abstract

Peat fires in Indonesia are predominantly anthropogenic and intensified by El Niño Southern Oscillation (ENSO)-related droughts. In recent decades, peat fires, which typically occurred in degraded areas (partially/entirely deforested peatlands), released massive amounts of carbon by burning the peat swamp vegetation and peat substrate. However, it could also influence atmospheric nutrient deposition, have a fertilizing effect on peatlands, and enhance their productivity. Little is known about how ENSO-related peat fires would affect the vegetation in times of little or no human impact. It is also unclear whether in the past such an ash-fertilization effect also occurred in the long term and how fires affected peatland carbon sequestration, which is one of their important ecosystem services. In order to understand this, we examine the fire regime, vegetation composition, nutrient status and carbon (C) accumulation rates of the Air Hitam and Sungai Buluh peatlands in Jambi, Sumatra, Indonesia during the Holocene. The results suggest that increased ENSO frequency and magnitude in the Late Holocene increased the fire occurrence and severity in both sites. During times of little human influence, those fires had little effect on peatland vegetation composition. The coincidence of more frequent fires, a nutrient enrichment and an increased carbon accumulation rate in the Late Holocene suggest that ash-fertilization might have also played a role in the recent past. Thus, low-severity fires could potentially enhance the peatlands' capacity to accumulate carbon if the water table is sufficiently high.