Effects of different fire severity levels on soil chemical and physical properties in Zagros forests of western Iran

Przemysław Szmit

The study focused on the effect of different intensities of fire on physical and chemical properties of soil in Zagros forests of western Iran. The dominant tree species in these forests is oak (Quercus persica). Three sites were selected; high severity burned site (HS), low severity burned site (LS) and control (not burned) site (C). Soil chemical properties such as: organic matter (OM), the total nitrogen (N), NO3-N, soluble potassium (K), soil phosphorus (P), pH, soil electrical conductivity (EC), cation exchangeable capacity (CEC), base cations (Ca, Mg, Na), CO2 and soil physical properties such as saturation percentage (SP), bulk density (BD), sand, clay and silt percentages were assessed in soil samples. To determine significance of differences among the three observed sites and most effective variables in the separation of sample plots, one-way analysis of variance and principal component analysis were used, respectively. Mean pH, N, NO3- N, OM, SP, P, K, and CEC at HS site were lower than at the sites with other fire intensities but the EC value for HS site was higher in comparison with other sites observed. According to Duncan's test, mean BD value for HS site was higher when compared with other sites but SP value was comparatively lowest. At LS site, mean sand content was lowest and the amount of silt was highest, in comparison with other sites. The results showed that observed fire severities had significant effects on physical and chemical properties of soil, yet fire low severity and control sites were very similar to each other in terms of investigated factors. Therefore, it can be concluded that low-severity fire regime has no significant influence on soil properties. In a management strategy, controlled low-severity fire regime can be an alternative management tool in improving soil conditions.