Recovery of Chilean Mediterranean vegetation after different frequencies of fires

Abstract

Post-fire recovery of sites in the Chilean Mediterranean vegetation were evaluated 20–30 years after the last fire. We mapped all fires that occurred between 1985 and 2015 in Central Chile using Landsat images. In order to conduct a spatial analysis of vegetation recovery and field sample, we chose sites burned between 1985 and 1995 that retained native vegetation and cover until 2015. In a sampled of these sites, richness and abundance of woody vegetation, and herbaceous richness were recorded. We contrasted our results from field sampling with control (unburned) sites at the species level. Generalized linear models (GLM) were used to evaluate the relationship between the percentage of vegetation recovered with fire frequency, pre-fire cover, topographic and geographic factors. In addition, GLM were used to evaluate the effects of fire frequency on species richness, abundance, and cover. We found that the proportion of dense and semi-dense vegetation cover were similar in sites burned once and twice, and higher than sites burned three times. Besides, the proportion of dense and semi-dense vegetation cover were higher in lower elevation sites, in those with higher slopes, and far from population centers. The richness and abundance of adult woody species, richness of regeneration and richness of native herbs, were greater in sites that had lesser fire frequency. Mean species richness of native herbaceous species decreased as fire frequency increased, exotic herbaceous cover had no relation with fire frequency, and both native and exotic herbaceous cover were greater at driest latitudes but were not related to fire frequency. Mean species richness after one fire was higher than in unburned sites, but some plant species were found only at unburned sites. We conclude that the Mediterranean vegetation of Chile is able to regenerate to pre-fire conditions after one and two fires, but three consecutive fires reduced its cover, richness and abundance, even 20 years after the fire.