Influence of burning and defoliation on Festuca costata (Nees) in the Drakensberg

Abstract

Fire occurs naturally in grasslands and savannas and it is commonly used as a management tool to influence structure and composition. The ability of a grass plant to recover from fire may be influenced by the fire frequency and intensity (influenced by seasonal weather conditions and fuel load), defoliation and competition from neighbouring plants. This study sought to investigate factors influencing the fire and herbivore dynamics of an evergreen C₃ grass, Festuca costata, in a high-altitude C₄ dominated grassland in the Drakensberg Mountains of South Africa. We experimentally examined the effect of fire frequency, defoliation and competition from neighbours on the growth dynamics of F. costata. Annual burning significantly decreased aboveground biomass production, number of tillers and tuft circumference of F. costata. Defoliation similarly reduced aboveground biomass production, number of tillers, tuft circumference and specific leaf area of F. costata. Competition from neighbouring plants reduced aboveground biomass production, number of tillers and tuft circumference of F. costata. Given the expected variable impacts of increasing CO₂ levels and temperature on C₃ and C₄ grasses, these results provide insights for managing the matrix of C₃ and C₄ grasses in the Drakensberg grasslands in a changing climate.