Fuel shapes the fire–climate relationship: evidence from Mediterranean ecosystems

Abstract

Aim To understand how vegetation mediates the interplay between fire and climate. Specifically, we predict that neither the switching of climatic conditions to high flammability nor the sensitivity of fire to such conditions are universal, but rather depend on fuel (vegetation) structure, which in turn changes with productivity. Location An aridity/productivity gradient on the Iberian Peninsula (Mediterranean Basin). Methods We defined 13 regions distributed along an aridity gradient, which thus differ in productivity and fuel structure. We then assessed the changes in the temporal fire–climate relationship across regions. Specifically, for each region we estimated three variables: the aridity level for switching to flammable conditions (i.e. climatic conditions conducive to fire), the frequency of these flammable conditions and the area burnt under such conditions. These variables were then related to regional aridity and fuel structure indicators. Results In mediterranean ecosystems, the aridity level for switching to flammable conditions increased along the aridity gradient. Differences in fire activity between regions were not explained by the frequency of flammable conditions but by the sensitivity of fire to such conditions, which was higher in wetter and more productive regions. Main conclusions Under mediterranean climatic conditions, fuel structure is more relevant in driving fire activity than the frequency of climatic conditions conducive to fire. At a global scale, fuel also drives the fire–climate relationship because it determines the climatic (aridity) threshold for switching to flammable conditions. Our results emphasize the role of landscape structure in shaping current and future fire–climate relationships at a regional scale, and suggest that future changes in the fire regime (i.e. under global warming) might be different from what it is predicted by climate alone.

Drought impacts on vegetation in the pre- and post-fire events over Iberian Peninsula

“…Accordingly, results suggest a certain level of fire selectivity for pixels presenting lower vegetative and water stress over spring and early summer, which emphasises the importance of fuel availability in fire occurrence over the Iberian Peninsula (Pausas and Fernández-Muñoz, 2011;Pausas and Paula, 2012).…”

The deforestation story: testing for anthropogenic origins of Africa's flammable grassy biomes

“…They differ strikingly from woody fuels characteristic of much of the Northern Hemisphere such as conifer woodlands and Mediterranean shrublands or the eucalyptus forests of southern and eastern Australia [59,60]. In these woody ecosystems, fuel continuity during large fires is coincident with hot dry conditions.…”

Estimating and Up-Scaling Fuel Moisture and Leaf Dry Matter Content of a Temperate Humid Forest Using Multi Resolution Remote Sensing Data

“…In areas of high vegetation productivity, such as this study, a small reduction in fuel moisture may enhance the dry matter productivity (i.e., an increase in dead fuel load and connectivity) [10], and therefore fuel consumption is increased by fire. LDMC is related to the lifecycle of a leaf and it shows the production of dry matter per leaf [11] and is a plant trait that sets the amount of dry material that is available for combustion [12].…”