Weather seasonality and pattern of thermochemical properties in vegetation living in the Mediterranean basin

Calorific value and flammability of vegetation are useful parameters to understand wildfire occurrence and behavior. Flammability and fuel calorific value of vegetation are influenced by several factors (structural and chemical properties, moisture content, etc.). The moisture content of living plants is one of the most critical parameter affecting fire ignition and propagation and represents an important variable in fire behavior modeling. Plant water content variations depend on both environmental conditions and ecophysiological characteristics of plants. The fuel calorific value, which influences the fire propagation and intensity, is mainly determined by chemical composition of species, growing conditions, and age of tissues. These characteristics could change throughout the year in relation to weather conditions and phenological phase of plants. Calorific value, flammability (ignition delay time, flame persistency, maximal height of flame), and live fuel moisture content (LFMC) of eight dominant species (Arbutus unedo L. Cistus salvifolius L., Cistus monspeliensis L., Erica scoparia L., Lavandula stoechas L., Phillyrea angustifolia L., Pistacia lentiscus L. and Rosmarinus officinalis L.) growing in two areas located in North Sardinia, Italy, were measured during two consecutive years. These Mediterranean shrub species are an important component of the understory vegetation that constitutes the surface fuels primarily responsible for the ignition and the spread of wildland fires in Mediterranean forests. Phenological phases and meteorological variables were also observed. In this paper, the influence of weather seasonal variations and phenology on LFMC and thermochemical parameters is evaluated and the relations between environmental conditions and thermochemical parameters are analyzed. In addition, biomass data of fine fuel components of some of the studied species are also reported with the purpose of analyzing the fire hazard in Mediterranean vegetation.