Demographic processes and fire regimes interact to influence plant population persistence under changing climates

Individual and interactive effects of changing climate and shifting fire regimes are influencing many plant species across the globe. Climate change will likely have significant impacts on plant population viability over time by altering environmental conditions and wildfire regimes as well as influencing species demographic traits. However, the outcomes of these complex interactions for different plant functional types under future climate conditions have been rarely examined. We used a proof-of-concept case-study approach to model multiple plant species across two functional plant types, obligate seeder and facultative resprouter, to examine the interactive effects of demographic shifts and fire regime change on population persistence across two landscapes of over 7000 km² in temperate southeastern Australia. Our approach involves a novel combination of a fire regime simulation tool with a spatially explicit population viability analysis model. We simulated fire regimes under six different future climates representing different temperature and precipitation shifts and combined them with 16 hypothetical plant demographic change scenarios, characterised by changes to individual or multiple plant demographic processes. Plant populations were more likely to decline or become extinct due to changes in demographic processes than in the fire regime alone. Although both functional types were vulnerable to climate-induced changes in demography, obligate seeder persistence was also negatively influenced by future fire regimes characterised by shorter fire intervals. Integrating fire regime simulations with spatially explicit population viability analyses increased our capacity to identify those plant functional types most at risk of extinction, and why, as fire regimes change with climate change. This flexible framework is a first step in exploring the complex interactions that will determine plant viability under changing climates and will improve research and fire management prioritisation for species into the future.