Determining fuel moisture thresholds to assess wildfire hazard: A contribution to an operational early warning system

ARGAÑARAZ JUAN P; LANDI M.A.; SCAVUZZO, CM; BELLIS, L. M.

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2018

1932-6203

Fuel moisture content (FMC) is an important fuel property for assessing wildfire hazard,since it influences fuel flammability and fire behavior. The relationship between FMC andfire activity differs among land covers and seems to be a property of each ecosystem. Ourobjectives were to analyze pre-fire FMC among different land covers and to propose a wildfirehazard classification for the Sierras Chicas in the Chaco Serrano subregion (Argentina),by analyzing pre-fire FMC distributions observed for grasslands, shrublands and forests andusing percentiles to establish thresholds. For this purpose, we used a fire database derivedfrom Landsat imagery (30 m) and derived FMC maps every 8 days from 2002 to 2016 usingMODIS reflectance products and empirical equations of FMC. Our results indicated thathigher FMC constrains the extent of wildfires, whereas at lower FMC there are other factorsaffecting their size. Extreme and high fire hazard thresholds for grasslands were establishedat FMC of 55% and 67% respectively, at 72% and 105% for forests and at 106% and 121%for shrublands. Our FMC thresholds were sensitive to detect extreme fire hazard conditionsduring years with high fire activity in comparison to average conditions. The differences inthe distributions of pre-fire FMC among land covers and between ecosystems highlightedthe need to locally determine land cover-specific FMC thresholds to assess wildfire hazard.Our wildfire hazard classification applied to FMC maps in an operational framework will contribute to improving early warning systems in the Sierras Chicas. However, moisture aloneis not sufficient to represent true fire hazard in Chaco forests and the combination with othervariables would provide better hazard assessments. These operational wildfire hazardmaps will help to better allocation of fire protective resources to minimize negative impact onpeople, property and ecosystems. To the best of our knowledge, this is the first study analyzingpre-fire FMC over several fire seasons in a non-Mediterranean ecosystem, aiming atassessing wildfire hazard