Chemical concentrations in overland flow from different forested areas in a Mediterranean environment: burned forest at different fire intensity and unpaved road

Chemical analyses of overland flow were made from samples taken in six diff erent land units. The objective was to determine the concentrations of the various chemical elements in surface runoff of each unit. Overland ilo iv p roduced during the three years of the study was also quantified in order to establish the ionic transport associated to each of the land units. Plots were placed in a forest with open and closed vegetation and in a burnt fore st, within which three levels of fire intensity were distinguished. An unpa ved road was also monitored. Results show that the burnt zones produced the highest ionic concentrations in the overland flow (600 mg/l), but after on e-year values had reverted to similar levels compared with other. Differenc es were also very high between similar open and closed vegetation forest (1 52 and 72 mg/l respectively in 1994). Unpaved roads play an important role, not only in the runoff generation but also in the chemical concentration ( 120 mg/l in 1994).