Effects of seasonal weather variations and phenology on live fuel moisture content and ignitability of mediterranean species

Maquis is an important component of Mediterranean vegetation characterized by high specific and structural heterogeneity and complexity. Flammability of vegetation is 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 behaviour modelling. Plant water content variations depend on both environmental conditions and ecophysiological characteristics of plants. As a consequence, knowledge of seasonal variation of ignitability and vegetation moisture content could contribute to identify critical periods of high ignitability risk in maquis ecosystems. Ignition delay time (ID time) 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.) of two areas located in North Sardinia, Italy, were measured during two consecutive years. Phenological phases and meteorological variables were also observed. Seasonal patterns of LFMC were compared with two drought meteorological indices. The aims of this work were to evaluate the influence of weather seasonal variations and phenology on LFMC and to analyze the relations between the seasonal patterns of LFMC and the pattern of two drought meteorological indices. Two typical seasonal patterns of ignitability were identified. Cistus salvifolius, Cistus monspeliensis, Lavandula stoechas and Rosmarinus officinalis seemed to be strongly sensitive to seasonal changes. They showed a clear increase of ignitability, during the drought period. For Arbutus unedo, Erica scoparia, Phillyrea angustifolia L. and Pistacia lentiscus the potential ignition risk of the live fine fuel appeared constantly high during the year and not strongly dependent on seasons. These patterns were strictly related to the seasonal variation of LFMC. Significant regression equations were found between plant moisture content and ID time. LFMC seasonal variations of Cistus salvifolius, Cistus monspeliensis, Lavandula stoechas and Rosmarinus officinalis were also well correlated to the drought indices.