Charcoal preservation and fire history in floodplain wetlands: problems and prospects

Fire plays an important role in floodplain wetlands, and wetland ecosystems respond dynamically in space and time to flooding, fire and geomorphological processes. Fire-climate-hydrology-vegetation interactions are complex and a multifaceted approach is required to understand and interpret fire history. This study investigated the use of macro-charcoal to interpret palaeo-fire regimes in the Macquarie Marshes. Sentinel Hotspot satellite data showed that Buckiinguy Swamp experienced 33 ignition points from 2002-2016, whereas Willancorah Swamp experienced 6 ignition points in this period. Macro-charcoal in contemporary sediment from Buckiinguy was used to estimate fluvial charcoal supply from upstream (13.5±3.2no. cm-3). Despite taking account of fluvial inputs, macro-charcoal in sediment profiles from both wetlands was highly variable. Buckiinguy had macro-charcoal up to 90 no. cm-3 in the upper 40 cm (mean charcoal accumulation rate; CHAR 0.55 cm-2a-1), and Willancorah had up to 450 no. cm-3 in the upper 60 cm (CHAR 3.75 cm-2a-1). Sedimentology, geochemistry, and carbon stable isotopes (δ13C range -15 to -25 ‰) were similar in both wetlands and quite uniform with depth. When combined with charcoal records, these proxies cannot be used with confidence to reconstruct local fire regimes.Water and wetland management could benefit from future palaeo-fire research if sufficient spatial and temporal assessment of fire and wetland conditions can be achieved.