Survival and growth of cactus species after a wildfire in central Argentina: Differences among species and the effects of microenvironment characteristics

Abstract

There are about 2200 cactus species, and most of them occur in fire-prone ecosystems. Nevertheless, there is scarce information about fire effects on the ecology of cactus species. In this study, we assessed the effects of a wildfire on the survival and growth of coexisting globose cactus species and their relation with microenvironment conditions in rocky outcrops from the Córdoba Mountains, central Argentina. A fire event occurred in spring 2011, and measurements were recorded in the first subsequent growing season, in winter. We selected 26 rocky outcrops and established three 3 × 1 m plots per outcrop. In each plot, we quantified all cactus individuals of the four species present in the area: Echinopsis aurea, Gymnocalycium bruchii, G. mostii and Parodia submammulosa. We also recorded if each individual cactus was dead or alive, and measured its size and post-fire growth. In addition, we measured the relative cover of rocks and bare soil, and the size of the rocks within a radius of 30 cm of each individual. Individual cactus survival (70–80%) did not vary among species. The highest post-fire growth was recorded in G. bruchii. For E. aurea, P. submammulosa and G. mostii, post-fire growth was negatively related to pre-fire size, suggesting that smaller individuals recovered faster than larger ones. Microenvironment characteristics did not affect post-fire growth in any of the species. Our results provide a preliminary insight into possible fire tolerance of globose cacti in the Córdoba Mountains, supported by their relatively high survival and growth after a fire event.