Interaction of Fire, Vegetation, and Climate in Tropical Ecosystems: A Multiproxy Study Over the Past 22,000 Years

Fire causes dramatic energy and matter exchanges between biosphere and atmosphere on a regional to global scale. Predicting fires, however, is hindered by the complex interplay of fire, climate, and vegetation. Paleo-fire records provide critical information beyond instrumental records that cover only the past few decades and may be used to assess the role of fire in large-scale and long-term environmental changes. Here we present a 22,000-year multiproxy record of fire regime from a sediment core retrieved offshore South Java, Indonesia. We use microcharcoal in combination with two molecular markers of burning, levoglucosan and polycyclic aromatic hydrocarbons, to reconstruct fire occurrence as well as fire intensity in the past. We show that fire occurrence and intensity were high during the Last Glacial Maximum (LGM; around 21,000 years ago) and low during the Heinrich Stadial 1 and the early Holocene. Both fire regime and vegetation in tropical regions with high annual rainfall were primarily controlled by rainfall seasonality. However, fire additionally stabilized the savannah (rainforest)-dominated ecosystem during the LGM (early Holocene) but caused transitions between the two vegetation types during the deglaciation and the late Holocene.