Effects and behaviour of experimental fires in grasslands, savannas, and forests of the Brazilian Cerrado

23 de dezembro de 2019

dez 23, 2019

Letícia Gomes, Heloisa S. Miranda, Divino V. Silvério, Mercedes M. C. Bustamante

An understanding of fire behaviour and its impacts on natural ecosystems is essential for developing management strategies, specifically for planning prescribed fires. It is well known that vegetation and microclimate factors are important predictors of fire behaviour. However, the relative importance of these factors and how fire behaviour responds to changes in these factors are still understood, especially in the Brazilian Cerrado, which has strong seasonality and high vegetation heterogeneity. Here, we compiled literature data from 65 experimental fire plots in three vegetation types in the Cerrado biome—grasslands, savannas, and forests—corresponding to a gradient of increasing of woody cover. First, we evaluated how aspects of fire behaviour (fire spread rate, fire intensity, and heat released) and of fire-associated emissions (fine fuel consumption, combustion factor, and carbon emissions associated with fine fuel consumption) vary according to vegetation type. Subsequently, we evaluated the relative importance of vegetation (represented by woody cover and fine fuel load) and microclimatic factors (represented by vapour pressure deficit [VPD] and wind speed) in determining the fire behaviour and fire-associated emissions.

Using generalised linear models, we evaluated the simultaneous influences of vegetation and microclimate variables (only for independent and non-collinear variables) on fire behaviour and fire-associated emissions. We found that aspects of fire behaviour and fire-associated emissions differed among the vegetation types: compared to forests, grasslands and savannas showed higher fire spread rates and fire intensities, consumed more fine fuel biomass, had larger combustion factors, released more heat, and emitted more carbon. The results show that the vegetation type, VPD and fine fuel load are key metrics for explain fire behaviour and fire-associated emissions in the Cerrado. The VPD was found to be the primary driver of the fire spread rate and fire intensity for all vegetation types and fine fuel load was the primary driver of heat released, fine fuel consumption, combustion factor, and carbon emissions in all vegetation types.

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