Fire regime, vegetation dynamics and land cover change in tropical peatland, Indonesia

This thesis seeks to understand and explain the role of fire in land cover change, vegetation and carbon dynamics in the carbon-dense, tropical peat swamp forest ecosystem of Southeast Asia. Following a methodological review, earth observation and ground data are employed to investigate fire regime, post-fire vegetation recovery, and fire-driven carbon losses in 4,500 km2 of peatland in Central Kalimantan, Indonesian Borneo. Results reveal an increasing trend in deforestation (2.2% yr-1 forest loss rate, 1973-1996; 7.5% yr-1, 1997-2005) and identify fire as the principal cause. A step change in fire regime is identified, with increasing fire frequency and reduced return interval following land drainage for the Mega Rice Project (MRP). During the post-MRP period (1997-2005), ~45% of the area was subject to multiple fires; 37% burnt twice and 8% three or more times. Extensive fires in 1997 and 2002 were associated with ENSO droughts, but fires in non-ENSO years (i.e. 2004, 2005) indicate fire incidence has decoupled from ENSO. This study provides a novel approach to quantifying relative magnitude of burn severity using characteristics of the post-fire vegetation regrowth. Combined spectral and ground data are used to demonstrate that enhanced fire frequency and burn severity limit post-fire forest recovery, with fern-dominated communities replacing tree re-growth. The character of post-fire vegetation is an important factor defining burning conditions for a subsequent fire, whilst fire frequency, severity and return interval influence both rate and nature of vegetation regrowth. Methods are proposed for deriving fire-driven carbon losses. Over the period 1973-2005, losses are estimated at 79-113 Mt of carbon (53-83 Mt from peat; 26-30 Mt from vegetation), with the greatest loss occurring during the post-MRP era (65-94 Mt). This work identifies the processes linking fire regime in tropical peatland to changes in vegetation ecology and carbon stocks and assesses the implications for ecosystem rehabilitation.