Mediterranean bioclimate zones of the world for the understanding of fire regimes

Aim: To quantify the role of soil fertility in the spatial variability of fire activity and to identify the mechanisms that drive this variability.

Location: The five Mediterranean-type climate regions of the world.

Time period: 2002 – present.

Major taxa studied: Terrestrial plants.

Methods: We compiled remotely sensed data on fire activity, climate, net primary productivity, and chemical soil properties for bioclimatically homogeneous zones within the five Mediterranean-type climate regions of the world. Putative direct and indirect effects of the environmental variables on fire activity were evaluated through structural equation modelling.

Results: Fire activity increased with net primary productivity, as expected for ecosystems with fuel-limited fire regimes. Soil acidity and the concentration of exchangeable aluminium also increased fire activity, supporting the idea that low fertility promotes plant characteristics that favour fire initiation and spread.

Main conclusions: Our research supports a positive relationship between wildfires and low soil fertility in Mediterranean-type climate regions across the globe. Therefore, soil fertility should be incorporated into models predicting future fires in a warming world.