Abstract
Most studies of climate change effects on fire regimes assume a gradual reorganization of pyrogeographic patterns and have not considered the potential for transformational changes in the climate-vegetation-fire relationships underlying continental-scale fire regimes. Here, we model current fire activity levels in Australia as a function of mean annual actual evapotranspiration (E) and potential evapotranspiration (E0), as proxies for fuel productivity and fuel drying potential. We distinguish two domains in space according to the dominant constraint on fire activity being either fuel productivity (PL-type fire) or fuel dryness (DL-type fire) and show that the affinity to these domains is related to fuel type. We propose to assess the potential for transformational shifts in fire type from the difference in the affinity to either domain under a baseline climate and projected future climate. Under the projected climate changes potential for a transformational shift from DL- to PL-type fire was predicted for mesic savanna woodland in the north and for eucalypt forests in coastal areas of the south–west and along the Continental Divide in the south–east of the continent. Potential for a shift from PL- to DL-type fire was predicted for a narrow zone of eucalypt savanna woodland in the north–east.
Highlights
Fire is a profound organizing force for ecosystems (Bowman et al 2009), a significant contributor to global biogeochemical cycles and a major influence on human populations in fireprone environments (Gibbons et al 2012, Chuvieco et al 2014, Moritz et al 2014)
To evaluate potential for qualitative changes in the processes underlying continental-scale fire regimes (‘transformational shifts’, as developed in paragraph) we focus on the relative importance of fuel productivity and fuel dryness constraints on fire activity levels
The form of the fitted F0.99 response surface (figure 2(a)) supported the hypothesized dichotomy of two distinct domains of climate limitation on fire activity: (i) relatively hot and dry environments where F0.99 was more sensitive to E than to E0 (i.e., productivity-limited fire (PL)-type fire), and (ii) relatively cool and humid environments where F0.99 was more sensitive to E0 than to E (i.e., dryness-limited fire (DL)-type fire)
Summary
Fire is a profound organizing force for ecosystems (Bowman et al 2009), a significant contributor to global biogeochemical cycles (van der Werf et al 2010) and a major influence on human populations in fireprone environments (Gibbons et al 2012, Chuvieco et al 2014, Moritz et al 2014). Fires occur across the continents with characteristic distributions of size, intensity, frequency and season, forming a small number of distinct ‘pyromes’, or broad syndromes of fire regimes (Archibald et al 2013). How these syndromes emerge from interactions of climate, vegetation, land use and human behaviour remains incompletely understood, hindering the predictions from dynamic global vegetation models (DGVMs) and other approaches that seek to predict land surface dynamics under global change (Kelley and Harrison 2014, Scheiter et al 2014). We propose a modelling framework for evaluating the potential for change in the average rate of burning (i.e. fire activity level) as well as for changes in fire type (i.e. transformational shifts) under altered future climates
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