Evaluation of some fuel moisture codes in Mediterranean shrubland of North Sardinia

The moisture content of dead fuel (dead twigs and leaves, fallen branches, litter, etc.) is an important variable in fire ignition and fire propagation modelling, because it is usually the driest and most likely to ignite during the summer season. Moisture exchange in dead materials is controlled by physical processes, and is clearly dependent on rapid atmospheric changes. Therefore, some meteorological danger indices, such as the three moisture codes of the FireWeather Index, address the modelling of the moisture dynamics of dead fuel. This kind of codes are mainly based on semiempirical equation and provide values that are classified in three or four fire danger classes usually ranging from low to extreme. Although several European Mediterranean countries have adopted part of the FWI in their forest danger forecasting, it was identified the need to perform further tests in order to calibrate and validate the codes also for Mediterranean environment. The FWI system was, in fact, designed for the Canadian environment which presents different characteristics if compared with Southern European countries in terms of both fuel types and weather conditions. The main objectives of this work is to evaluate the potential use of the FWI moisture codes in describing dead fuel moisture content pattern for Mediterranean shrubs. The study was carried out in Sardinia (Italy). Moisture content of dead fuel (1 hour and 10 hours fractions) was determined periodically during four consecutive years on three Mediterranean shrub species: Cistus monspeliensis L., Pistacia lentiscus L., and Juniperus phoenicaea L. Meteorological variables and temporal patterns of moisture content, measured by using humidity sensors, were also recorded. Therefore, we used FMC values by sensor measurements to calibrate the fuel moisture codes in our environment. Finally, in order to develope different treshold values of danger more appropriate for mediterranean climate, percentile analysis was applied and new fuel moisture code classes were defined.