Fire regimes and soil erosion in north Australian hilly savannas

Abstract

Soil erosion is recognised as a major landscape management issue in northern Australia, given highly erodible soils, and high rainfall erosivity associated with low soil surface cover and intense storm events at the commencement of the wet season. Although recent continental-scale erosion modelling addresses such conditions, it does not take account of contemporary fire regimes dominated by annual, late dry season wildfires, especially in extensive higher slope (≥5%) regions of monsoonal Australia. The present paper reports a simple erosion pin assessment at two sites, contrasting soil loss and movement on unburnt and late dry season-burnt hillslopes over one wet season. Although very significant erosion was observed on both unburnt and burnt treatments, overall there was roughly three times the net soil loss and two times more soil movement on late dry season-burnt plots. The landscape scale of late dry season fire regimes, and implications for increased impacts of soil erosion on soil organic matter, nutrients, and ecosystem health are discussed. Collectively, assembled data suggest that more attention needs to be given to understanding and managing the impacts of contemporary fire regimes on hillslope soil erosion processes in the seasonal Australian tropics.