Prescribed underburning before resin tapping does not affect resin yield in Pinus pinaster Ait. stands

Aim of study: To assess the effect of prescribed underburning (PB) and tapping on resin yields in maritime pine stands. We hypothesized that PB reduces fire hazard, generates stress at the cambium level and potentially increases the number of resin canals and resin yield after tapping. Area of study: Northern Plateau of the Iberian Peninsula, central-eastern Spain. Material and methods: Six 50 m x 50 m plots were established in a Pinus pinaster Ait. stand, three of which were burned and tapped in 2018 and three controls plots (tapped only). Resin yield was monitored in 90 trees over four years (2018-2021). A Generalised Linear Mixed Model (GLMM) for repeated measures was used to analyse resin production. Average resin yield per tree was predicted by Treatment as a fixed between-subject factor (two levels: Tapping only vs PB+Tapping) and years as within-subject factor (four levels: 2018, 2019, 2020, 2021). Plot and tree were considered random factors. Main results: The GLMM revealed the significant effect of time (years after tapping), plot and tree. However, the potential effect of meteorology (time), site (plot) and the interaction between fire and individual trees (stress that potentially increases number of resin canals) did not generally have any effect on resin yield at stand level. The resin yield was maintained in burned and tapped plots relative to the tapped only control stand. Research highlights: Prescribed underburning before tapping in order to reduce fire hazard is compatible with tapping P. pinaster stands but does not increase the resin yield.