Fires are ecological disturbances that change the structure of populations, and accordingly demographic response is determined by the particular attributes of each species. The present study evaluates the effect of fire on a population of Hypericum styphelioides subsp. styphelioides through its population structure. The structure of the population in unburned and burned areas was characterized. In the burned area, medium reproductive adult occurs in larger numbers and its density is higher in comparison to the unburned area, this pattern could have been determined by a post-fire population explosion. On the other hand, the classes below the medium reproductive adult were less represented in the burned area, probably as a consequence of the continue decline on the recruitment of younger individuals of each generation due to the reduction of nutrient levels after the fire. This pattern matches the similarity of the densities of these performance classes and the overall density between both areas. Furthermore, the smaller dimensions found in medium and small breeding adults in the burned area of the pine forest also indicates the nutrient deficiency that affected the growth of the individuals after the fire. However, similar dimensions found among vegetative adults of both areas may indicate the recovery of the levels of nutrients in the burned area of the pine forest to the pre-fire levels, by the accumulation of organic matter.
