Abstract
Abstract. Fire is the primary disturbance factor in many terrestrial ecosystems. Wildfire alters vegetation structure and composition, affects carbon storage and biogeochemical cycling, and results in the release of climatically relevant trace gases including CO2, CO, CH4, NOx, and aerosols. One way of assessing the impacts of global wildfire on centennial to multi-millennial timescales is to use process-based fire models linked to dynamic global vegetation models (DGVMs). Here we present an update to the LPJ-DGVM and a new fire module based on SPITFIRE that includes several improvements to the way in which fire occurrence, behaviour, and the effects of fire on vegetation are simulated. The new LPJ-LMfire model includes explicit calculation of natural ignitions, the representation of multi-day burning and coalescence of fires, and the calculation of rates of spread in different vegetation types. We describe a new representation of anthropogenic biomass burning under preindustrial conditions that distinguishes the different relationships between humans and fire among hunter-gatherers, pastoralists, and farmers. We evaluate our model simulations against remote-sensing-based estimates of burned area at regional and global scale. While wildfire in much of the modern world is largely influenced by anthropogenic suppression and ignitions, in those parts of the world where natural fire is still the dominant process (e.g. in remote areas of the boreal forest and subarctic), our results demonstrate a significant improvement in simulated burned area over the original SPITFIRE. The new fire model we present here is particularly suited for the investigation of climate–human–fire relationships on multi-millennial timescales prior to the Industrial Revolution.
Highlights
The CryosphereFire is one of the most important disturbance processes affecting the terrestrial biosphere
Since we focus on the overall performance of the model in simulating fire behaviour and impacts on ecosystems, and since the development of the demographic history data sets is the subject of a separate publication, we exclude anthropogenic ignitions from the simulations presented here
Using monthly climate forcing constrains total precipitation amount and number of wet days, but the timing of rainy days within a given month may be very different in the simulation compared to the true weather situation, e.g. if simulated wet days all come clustered at the beginning or end of the month, whereas in reality they had been more distributed over the month
Summary
The CryosphereFire is one of the most important disturbance processes affecting the terrestrial biosphere. Fires affect most ecosystems from tropical forests to tundra (Bond and van Wilgen, 1996; Dwyer et al, 2000), and the evolution of fire over the Phanerozoic is likely to have had a major control on both the global carbon budget and the present distribution of plants on earth (Bond and Keeley, 2005; Pausas and Keeley, 2009; Bond and Scott, 2010; Bond and Midgley, 2012). Biomass burning (both wildfires and intentional combustion of biofuels) influences the spatial and interannual variability in the emissions of climatically relevant trace gases and aerosols, including CO2, CO, CH4, NOx, and black carbon (Crutzen and Andreae, 1990; Penner et al, 1992; Andreae and Merlet, 2001; Jain et al, 2006).
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