Historical fire frequency (1779-2013) in pine-oak forests in the community of Charcos, Mezquital, Durango

Historical fire regimes were reconstructed using dendrochronological methods to provide basic information for understanding this phenomenon. In order to reconstruct the fire history in a pine-oak forest in Mezquital, Durango, we collected 78 samples from different fire-scarred tree species (Pinus durangensis, P. arizonica, P. ayacahuite, P. teocote and Pseudotsuga menziesii); 73 and 27 % of the samples were taken from live and dead trees, respectively. By applying dendrochronological methods a total of 75 samples (96 %) and 535 fire scars were dated. Fire regimes were reconstructed from 1746 to 2013, with 1779 being the year of the first recorded fire. A mean fire interval (MFI) of 2.0 years and a Weibull median probability interval (WMPI) of 1.8 years (all scars) were reconstructed. Considering 25 % of scars or more (large fires), a MFI and a WMPI of 7.0 and 5.9 years, respectively, were determined. In total, 92.2 % of fires were categorized as having occurred in the spring and only 7.8 % in the summer. There was no significant (P < 0.05) influence of rainfall and the El Nino Southern Oscillation (ENSO) on fire frequency; however, extensive fires were positively associated with decreased rainfall and ENSO events (La Nina phase).