The effects of fire on soil organic carbon quantity and nutrients availability in Sardasht Oak forests

Most of soil physical, chemical and biological properties change by fire. Fire can influence forest soils fertility by altering nutrients content and availability. In order to investigate fire impact and different firing background on some soil chemical properties, 80 soil samples were taken from two depths (0-5 cm and 5-20 cm) with different time of firing background (6 and 12 months). Total nitrogen, phosphorus, potassium, manganese, iron, zinc, copper and organic carbon were measured in soil samples. The results showed that there was a significant difference in the amount of phosphorus and nitrogen between burned and control soils. The amount of studied indices increased after firing in burned soils compared to control ones, however one year later they reach to their pre-fire levels. Phosphorus and coarse fraction carbon (0.25-2 mm) in burned soils were 2.23 and 2.53 times higher as compared to unfired samples, respectively. Manganeseamount in soils with 6 months firing history increased 32.7 percent in comparison to control soils, but one year after firing its content decreased. The most potassium amount (392 mg kg-1) observed in burned soils with 12 months history of burn. Therefore forest firing causes obvious changes in soil properties but these changes are not permanent and depending on fire intensity, impression permanency duration is different.