The response of springtails to fire in the fynbos of the Western Cape, South Africa

Although fire is a natural form of disturbance in many ecosystems, the frequency of fires is increasing due to human activities. Hence, understanding the impacts of fire on biodiversity and ecosystem functioning has become increasingly important. In this study we investigated the effects of a large-scale fire on an important soil-dwelling group, springtails (Collembola), one year before and for three consecutive years after a fire in the fire-prone fynbos ecosystem in South Africa. In particular, we investigate the resistance of the springtail assemblages (i.e. their ability to remain relatively unchanged in the face of a disturbance), and their resilience (i.e. ability to return to a pre-disturbance state). To do this we sampled two sites with contrasting vegetation (Erica and Protea) and used three different standardized litter types in litterbag traps. A total of 35 springtail species from 31 genera and 14 families was found. The springtail assemblages in this fynbos system showed slightly more resistance to fire than resilience after the fire event, though substantial variation was found among vegetation types. Mean species richness and abundance per litterbag varied among the Protea and Erica sites, with resistant species being dominant in the Erica site, while species that showed an increase after the fire were dominant in the Protea site. Differences were also found between life forms: atmobiotic (free-living in vegetation) and epiedaphic (surface dwelling) species showed a significant decline in mean species richness directly after the fire in the Erica site. Euedaphic (soil-dwelling) species richness remained unchanged post-fire in the Erica site, while actually slightly increasing after the fire in the Protea site. Although the fynbos springtail assemblages had not fully recovered to pre-fire abundance after three years, many species appear to be resistant to or recover rapidly after fires, at least as ascertained over the relatively short (four years) duration of the study. It is likely that this response is influenced by the presence of suitable refugia within sites and by species-specific traits. Given changing fire regimes and the increasing frequency of fires due to human disturbances, the system will likely become more dominated by resistant springtail species preferring nutrient rich circumstances and easily decomposed litters.