Impact of fire frequency on woody community structure and soil nutrients in the Kruger National Park

Although fire is recognised as an important determinant of the structure and function of South African savannas, there are few studies of long-term impacts. Controlled burning blocks of contrasting fire season and frequency have been maintained throughout the Kruger National Park for almost 50 years. This paper reports on a quantitative study of the Satara plots to determine the long-term impacts of fire frequency on woody community structure and soil nutrients. Increasing fire frequency significantly decreased woody plant basal area, biomass, density, height, and mean stem circumference. The number of stems per plant and the proportion of regenerative stems increased with increasing fire frequency. Effects on species richness of woody plants were inconsistent. There were no significant differences attributable to fire frequency for any of the soil variables except organic matter and magnesium. Organic carbon was highest in the fire exclusion treatment and lowest in soils from plots burnt triennially. Magnesium levels were greatest in the annually burnt soils and least in the triennial plots.