Fire in floodplain wetlands

Fire plays an important role in floodplain wetlands, which respond dynamically to flooding, fire and geomorphological processes. A multifaceted approach is required to understand and interpret their fire history. Fire mapping and analysis of sediment and macro-charcoal from contemporary fluvial deposits were used to assess and interpret past fire regimes in the Macquarie Marshes. After accounting for fluvial macrocharcoal flux from upstream sources, local macro-charcoal in ~1 m deep sediment profiles accumulated over the last ~1.7 ka were highly variable and inconsistent between cores in two core wetlands (concentrations 0 to 438 no. cm-3, mean accumulation rates 0 to 3.86 no. cm-2 a-1). A positive correlation existed between the number of recent fires, satellite-observed ignition points, and macro-charcoal concentrations at the surface of the wetlands. Sedimentology, geochemistry, and carbon stable isotopes varied little with depth and were similar in both wetlands. Application of macro-charcoal and other environmental proxy techniques is inherently difficult in large, dynamic, and patchy wetland systems due to variations in charcoal sources, sediment and charcoal deposition rates, and the prevalence of taphonomic processes. Future palaeo-fire research could benefit wetland management if sufficient spatial and temporal analysis and assessment of fire, flood and other environmental conditions can be achieved.