Effect of burn area on invertebrate recolonization in grasslands in the Drakensberg, South Africa

Abstract

Our study examined the short-term response of grassland invertebrate communities to fire in the South African Drakensberg, in relation to distance from the edge of a burn. We aimed to establish which species survive fire and the dynamics of the post-fire recolonization process, and thereby contribute to establishing the ideal area of a prescribed burn for invertebrate conservation. Four transects were sampled two and 12 weeks after burning. Along each transect one unburnt control and four burnt sites were quantitatively sampled. Richness, abundance and diversity were calculated for each site and canonical correspondence analysis was applied to transect and morphospecies counts to determine the impact of distance from the edge of the burn on community structure. Distance from burn edge affected invertebrate richness and abundance, especially for flying insects. Burning appeared to minimally impact on wingless invertebrates, suggesting they tolerated fire by finding refuge. Invertebrate community structure changed with increasing distance from burn edge two weeks, but not 12 weeks post-burn. A distance of 280 m from burn edge appears to allow sufficient recolonization to maintain invertebrate diversity. Taxa found in the unburnt control and site closest to the edge in burnt grassland may be fire sensitive and require further study.

Keywords: invertebrates, fire, grasslands, recolonization, Drakensberg