Integrating Plant Evolution into the Study of Fire in the Earth System

Wednesday, 17 December 2014
Sally Archibald, University of the Witwatersrand, Johannesburg, South Africa and Caroline Lehmann, University of Edinburgh, School of GeoScienes, Edinburgh, United Kingdom
20% of the Earth’s land surface burns annually representing a critical exchange of energy between the land and atmosphere via combustion. Fires range from small spreading surface fires to intense dramatic crown fire events, depending on the fuels and climate where they burn. Fire is a powerful selective force on plants: over the last 420 million years the plant traits required to tolerate fire, and in some cases to promote particular types of fire regimes have evolved. However, most Earth System studies focus on the links between climate and fire, ignoring the fact that these relationships are mediated by the fuels – by plant structure and function. We argue via multiple lines of evidence that the flammability of an ecosystem is influenced by the vegetation present, and that this vegetation is not a passive outcome of certain climate and fire properties, but is also the result of evolutionary forces, biological and biophysical feedbacks and biogeographic contingencies. Hence, understanding current patterns of fire and vegetation, as well as longer-term patterns of fire over deep time, requires a framework that can incorporate evolution and biogeography, and in particular, plant traits.