Using 137Cs measurements to estimate soil erosion rates in forest stands affected by wildfires. Results from plot experiments

The destruction of forest cover by wildfires has important consequences on the stability of forest ecosystems. It is well recognized that forests play a key role in regulating the hydrological cycle by modifying rainfall interception and evapotranspiration but also affecting hydrological and erosion responses of the soil surface. For these reasons, in areas devoted to forestry, wildfires can cause loss of biomass production and serious off-site problems related to overland flow and the amount of sediment delivered downstream. Quantifying the consequences caused by wildfires on the soil surface in terms of runoff and soil loss is a great challenge for scientists and foresters. In this paper, a plot experiment aimed at evaluating the effects on soil erosion by wildfires of different severity is firstly described. The experiment was carried out in 1999 in three small plots, located in Southern Italy, covered by pine trees planted in the early ‘60s. The results obtained from this experiment provided evidence of a short-time effect of wildfire on soil erosion. However, the normal conditions of the pre-fire period seemed to be re-established after a few months following fire. In order to explore possible long-term effects on soil loss, estimates of soil erosion provided by recent 137Cs measurements carried out in the same plots were made. The overall results indicated, for the study area, the absence of a long-term effect on soil erosion caused by the passage of fire and suggested that the 137Cs technique can be a useful tool to explore the effect of wildfires in forested ecosystems.