Survival to prescribed fire of plantation-grown Corsican black pine in northern Portugal

The current fire regime threatens black pine (Pinus nigra Arn.) persistence in the Mediterranean Basin, which recommends larger-scale fuel treatments. Prescribed burning is an option for stand protection but its use in young stands (which are particularly at risk) is hindered by the scarce knowledge on post-fire tree survival. The objectives were to characterize bark thickness as a fire-resistance trait in P. nigra and to describe how post-fire tree survival responds to tree size and fire effects in a 16-year-old plantation. Bark thickness was related to diameter at breast height and height in the stem. Metrics describing tree size and stem and crown damage were measured 1 year after prescribed burning in 259 trees. Tree survival was modeled with logistic regression and Classification and Regression Tree analysis. Bark thickness increased linearly with diameter at breast height (dbh) and decreased with height in the stem. Tree survival was primarily a function of crown injury. Stem damage was an influent factor in small trees. Due to thinner bark and lower tolerance to crown damage, young P. nigra trees are less fire-resistant than other Mediterranean pines, e.g., Pinus pinaster. Prescribed fire should not be attempted if dbh < 10 cm. Mechanical clearing is the treatment of choice in young stands with a significant shrub layer.