Effects of burning on heathland soil chemical properties: an experimental study on the effect of heating and ash deposits.
The role of heat and nutrient supply from ash after light and hot fires on Brittany (France) heathland soils (brown acidic soils) were studied in the laboratory. The soil surface was heated either to 150 °C for 15 min or 300 °C for 30 min and the effects of the percolation of two ash solutions were studied. Soil heating had a significant effect on soil properties only at 300 °C. The OM content decreased during this treatment inducing a decrease in cation exchange capacity and in exchangeable bivalent cation concn. The nutrient inputs from ash did not compensate for these losses, except in the case of K. Nearly all Na was leached and its exchangeable concn always remained lower than the control samples. Moreover, the major part of nutrient input by ash was immobilized as insoluble forms. The results suggested that a hot burn had transient effects on the soil fertility of these heathlands and that repetitive fires induced a loss of nutrients and an impoverishment of the ecosystem. They contributed to the maintenance of the low fertility of these soils and the vegetation communities.