The effect of forest fires on the dynamics of some soil physical, chemical and biological characteristics over time

In order to study the effect of fire on some physical, chemical and biological characteristics of soil, 36 sample plots with three low, medium and high fire intensities and control treatments were set up in the Namkhaneh district of University of Tehran Forest. Soil samples were then taken from 0-10 cm layer in three phases (one day, 6 and 12 months after the fire) and some soil properties were studied. Data analysis was done by repeated measures ANOVA in SPSS software. The results showed that fire intensity had no significant effect on soil physical properties including bulk density, moisture content and soil texture. The results of soil chemical properties analysis showed that fire intensity had a significant effect on electrical conductivity, organic carbon, total nitrogen, carbon to nitrogen, phosphorus, calcium, potassium and magnesium ratios but had no significant effect on pH. In terms of biological characteristics, fire intensity had no significant effect on carbon microbial biomass but on microbial respiration and nitrogen microbial biomass. Time after fire had significant effect on moisture content, microbial respiration, microbial carbon and nitrogen, available phosphorus and potassium but had no significant effect on other physical, chemical properties. Since fire causes long-term depletion of soil nutrients, some post-fire preventive and rehabilitative measures in areas with moderate and high fire severities are required to restore soil functions more quickly.