Fire severity as a key factor in post-fire regeneration of Pinus pinaster (Ait.) in Central Portugal

Abstract

Context: Mediterranean pine woodlands are strongly affected by wildfires; however, there are knowledge gaps in the role of fire severity on Pinus pinaster Ait. regeneration. Objectives: The principal questions were: (a) does post-fire regeneration of Maritime Pine differ where canopies were consumed to a low vs. high degree and (b) which factors, besides fire severity, could explain these differences. Methods: Pine recruitment was monitored from 2 to 36 months after a summer wildfire in 18 25 m2 plots, equally dividedovertwofireseverityclassesbasedoncrownconsumption. Besides the degree of crown consumption, three quantitativefireseverityindicesaswellaspost-firesiteconditions,seed input and understory vegetation recovery were measured. Results: Pine seedling densities were consistently higher in the plots with low than high crown consumption but due to marked spatial variability, they were only significantly different at two out of the eight sampling occasions. This variability could be explained by a quantitative index based on the diameter of twigs, as well as by seed input and postfire site conditions (ash and litter cover). Conclusion: Fire severity was found to strongly affect the pine recruitment following wildfire, using both a qualitative visual severity index and a quantitative, more labourintensive one.