Fire scar characteristics in two tropical montane conifer species from central Mexico

Abstract

Fire scar analysis is a fundamental tool for reconstructing fire regimes in conifer forests. However, little is known about fire scar properties in tropical montane conifers, where some assumptions limit dendroecological research. These include that fir species do not exhibit external fire scars and that pines without external fire scars have not experienced past fires. This study describes fire scar patterns in two conifer species growing in Mexican temperate forests: sacred fir (Abies religiosa) and smooth-bark Mexican pine (Pinus pseudostrobus). We extracted cross-sections from 110 trees and measured tree age, basal diameter, bark thickness, fire scar size and seasonality, the number of scars per tree, years and basal diameter from pith to the first scar, and the proportion of external and buried fire scars. Most trees had three fire scars, which appeared during the dry season after the first 15 years measured from the pith. Old and large-diameter trees did not have more fire scars, but the time between fire scars influenced fire scar closure in sacred firs. Bark thickness and the proportion of visible and buried fire scars were similar in both species. Our results suggest that the absence of visible fire scars in smooth-bark Mexican pines does not imply the absence of fire, and sacred firs can exhibit external fire scars like pines.