CAN FOSSIL PLANT TRAITS TELL US ANYTHING ABOUT PALEOFIRE REGIMES?

The fossil record of charcoals reveals that wildfires have occurred on our planet for 410 million years (Glasspool et al. 2004). Our modern ecosystems exhibit a range of different fire regimes defined by the patterns of fire seasonality, frequency, size, intensity, type and severity. Because fire regime includes so many interlinked aspects of fire that we cannot yet estimate for the past, it is difficult to discern for paleofire events. Paleofire studies typically rely on assessing the abundance of fossil charcoals in rocks and sediments (see Scott, 2000 for a review), which allows paleontologists to identify variations in fire frequency (Marlon et al., 2009). It is also possible to study the fuel by observing the botanical affinities of fossil charcoals (Scott, 2000) and more recent research has quantified the temperature of formation of charcoals using reflected light microscopy (McParland et al. 2009). However, few paleofire studies utilise either of these latter sources of information. Paleofire science therefore most typically focuses on estimating the fire frequency component of fire regime. Fire intensity, fire severity and fire frequency are key components of fire regime and these are influenced strongly by plant traits, which influence fuel structure and govern the amount and rate of energy released from a fire and in turn how much energy is transfered to the ground and other plants (Davies, 2013). The ability to estimate variations in fire intensity and severity would therefore markedly improve our understanding of the effects of paleofires on ecosystems. From their fossil remains, we know much about the types of plants that have grown throughout Earth’s history via reconstructions of plants and ecosystem. Of importance to fire are the traits of leaf size and shape, which can be observed in leaf fossils; both these traits are known to impact upon to litter flammability (Schwilk and Caprio, 2011). Building on such trait based approaches we consider the influence of Leaf Mass per Area [LMA: dry mass / fresh area (Wright et al., 2004)] on litter flammability where LMA is a trait that is measurable from fossil leaves (Royer et al. 2007). Our aim is to begin to provide paleo-suitable information on plant trait-flammability relationships that we may be able to start utilising in our intepretations of paleofires in Earth’s past.