The effect of fire-management on invertebrates within a South African savanna.

Abstract

Fire plays a key role in determining the structure and function of savanna ecosystems, without which the characteristic open grassland would be lost, along with the high biodiversity it supports. Over recent decades human development has meant that savanna systems have become heavily utilised, requiring burn management to be undertaken. As savannas are regarded as fire-prone systems, this practise had become an unquestioned tradition. Despite the wide use of burn regimes as a management tool, little is known about the effect of burning on non-focal taxa.

This study looks at both the long and short-term effects of burning, in a South African game reserve, on invertebrates within a patch mosaic structure. Since invertebrates encompass a broad group of organisms, analysis was divided into three levels based upon location within the ecosystem. Changes in the abundance and diversity of invertebrates at ground level, grass level and tree level were studied. The short-term study showed that ground invertebrate abundance increased following a burn event, whereas, grass and tree invertebrates showed declines. Analysis of invertebrate abundance and diversity within six different burn ages enabled the long-term effects of a patch mosaic burn regime to be monitored. Ground invertebrate abundance was high in recently burnt patches compared to undisturbed sites. Grass invertebrates declined immediately following the burn event in the short-term study; however, abundances remained similar across the burn ages in the long-term study. In contrast to grass and ground invertebrates, the abundance of tree invertebrates increased as the level of disturbance decreased; with the highest abundance being found in the unburnt site.

This study provides a general understanding of the effect burning can have on the invertebrate community; while opening new doors into a relatively untouched subject. Future research into this would be beneficial for the maintenance of the complex savanna ecosystem.