| Summary: | 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.
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