Combining optimization and simulation modelling to measure the cumulative impacts of prescribed fire and wildfire on vegetation species diversity

摘要

1.Growth-stage optimization (GSO) offers a new approach to biodiversity conservation in fire-prone regions by estimating the optimal distribution of vegetation growth stages that maximize a species diversity index.This optimal growth-stage structure provides managers an operational goal explicitly linked to a positive conservation outcome but does not define the fire regime needed to achieve it.2.We paired GSO with LANDIS II,a landscape succession and disturbance simulation model,to (a) estimate the optimal growth-stage structure that maximized vegetation diversity in a south-east Australian heathy woodland,(b) define the fire regime needed to achieve it,and (c) determine the cumulative effects of different fire-regime scenarios on vegetation diversity over a 60-year period.Scenarios included 0%,2%,5%,and 10% of the landscape burnt per year by prescribed fire only,or in combination with three alternative wildfire regimes.Furthermore,we investigated the differences in the optimal growth-stage structure relating to above-ground,soil seedbank,and total (above and soil seedbank) diversity datasets.3.The growth-stage structure that maximized total vegetation diversity comprised approximately even proportions of all stages.In contrast,separately analysed above-ground and soil seedbank data resulted in a greater proportion of younger and older growth-stages,respectively.4.Scenarios including 5% prescribed burning per year (with and without wildfire) resulted in diversity values within 1.5% of the theoretical maximum value.Scenarios including 2% and 10% prescribed fire resulted in diversity values 8%– 12% and 1.5%–5% lower than the maximum,respectively.Scenarios without prescribed fire caused diversity to fall 30%–70%.Trends across the 60 years showed that wildfire depressed diversity and subsequent prescribed fire drove recovery within 15 years.The largest threat to vegetation diversity was the absence of fire.5.Synthesis and applications.Combining growth-stage optimiza