Preliminary assessment of the impact of long-term fire treatments on in situ soil hydrology in the Kruger National Park

Abstract

There has been significant attention focused on the impacts of fire frequency and season of burn on ecological processes in the Kruger National Park (KNP). Whilst there has been some examination of these fire effects on soil properties, the explicit linkages of these effects to the hydrology of soils in burnt areas has remained a gap in our understanding. During August 2010, a field scoping campaign was undertaken to assess the impacts, if any, of long-term fire treatments on the hydrology of soils on the experimental burn plots (EBPs) in the KNP. Using various hydrometric and soil physical characterisation instruments soil, hydraulic conductivity and soil strength variations were determined across the extreme fire treatment on the EBPs, the annual August (high fire frequency) plots and the control (no burn) plots, on both the granite and basalt geologies of Pretoriuskop and Satara, respectively. It was found that there were soil hydrological and structural differences to fire treatments on the basalt burn plots, but that these were not as clear on the granite burn plots. In particular, hot, frequent fires appeared to reduce the variation in soil hydraulic conductivity on the annual burn plots on the basalts and led to reduced cohesive soil strength at the surface.

Conservation implications: The KNP burn plots are one of the longest running and well studied fire experiments on African savannahs. However, the impacts of fire management on hydrological processes in these water-limited ecosystems remains a gap in our understanding and needs to be considered within the context of climate and land-use changes in the savannah biome.