Identification of flavonoids in Pinus Laricio needles and changes occurring after prescribed burning

Prescribed burning is increasingly being used as a fire prevention tool in forest management; however, it can cause thermal stress to trees. Its effects on pine physiology have been poorly understood. Flavonoids are highly indicative of plants’ responses to environmental stress, and in this study, we used flavonoid concentrations in pine needles to assess fire impact on a Corsican Pinus laricio Poir. forest up to 4 years after prescribed burning. This is the first study that highlighted the presence of flavonols in P. laricio and indicated kaempferol to be the major compound. The total flavonol content increased by 60% 3 months after 1 or 2 prescribed low-intensity burnings and returned to the pre-burning level after 1 year. This suggests that thermal stress events caused defensive production of flavonoids. Prescribed burnings performed at 3-year intervals did not appear to alter flavonoid levels. In the light of these findings, forest managers may consider the use of prescribed burning at 3-year intervals as a means to reduce fuel loads, while minimizing the impact on P. laricio.