Abstract

QUINTERO-GRADILLA, Shatya Devi et al. Post-fire change in structure and composition of the tree stratum and fuel load in a Pinus douglasiana forest in Mexico. Madera bosques [online]. 2019, vol.25, n.3, e2531888.  Epub May 15, 2020. ISSN 2448-7597.  https://doi.org/10.21829/myb.2019.2531888.

In pine forests with an historical fire regime of frequent low severity surface fires, under extreme weather conditions or a consequence of fire suppression, the severity of fires may increase. Response of vegetation to severe fire events was studied in a chronosequence of 8 years, 28 years and 60 years in a forest dominated by Pinus douglasiana in Mexico. Tree density (> 2.5 cm diameter) reached values of 1095 stems ha-1 ± 609 stems ha-1 and a basal area of 10.0 m2 ha-1 ± 2.2 m2 ha-1 in the 8 years stands; 28 years after stand-replacement fires, basal area (44.6 m2 ha-1 ± 3.0 m2 ha-1) was close to that of 60-year-old stands (49.0 m2 ha-1 ± 6.4 m2 ha-1). Pines showed the highest importance value across the chronosequence; with post-fire time, a formation of a sub-canopy of shade-tolerant broad-leaved species and an increase in species richness and diversity was observed. Long periods without fire increased surface fuel loading (66.0 Mg ha-1 ± 5.5 Mg ha-1 for 28 years and 61.5 Mg ha-1 ± 4.6 Mg ha-1 for 60 years-old stands) and changed fire behavior (spread velocity increased from 1.3 m s-1 to 4.1 m s- 1 and flame length from 0.7 m to 1.7 m between the 8 years stands and 28 years - 60 years stands combined). Results suggest that the fire suppression policy in pine forests should be evaluated considering the balance between biological conservation goals and mitigation of high severity fire danger.

Keywords : mixed pine-hardwood forests; species diversity; forest fuels; fire regimes; stand-replacement fires; Sierra de Manantlán Biosphere Reserve.