Impacts of two spatially and temporally isolated anthropogenic fire events on soils of oak-dominated Zagros forests of Iran.

Anthropogenic fires have varying effects on the oak-dominated forests of the Zagros Mountains in western Iran. The objective of this project was to investigate the effects of fire on various components of soil. For this purpose three homogeneous and neighboring sites were inspected. Site A was the unburned control. Sites B and C experienced fires about 2 and 8 years prior to the study, respectively. In comparison to the control, site B showed a decline in organic matter content (1.69 ± 0.24 vs. 1.13 ± 0.17), N amount (0.40 ± 0.05 vs. 0.19 ± 0.03), litter depth (1.20 ± 0.214 cm vs. 0.087 ± 0.044 cm), germinated seedlings (272 ± 40 vs. 75 ± 25), earthworm biomass (3.4 g/kg vs. 0.26 g/kg), and plant diversity (1.95 ± 0.30 vs. 1.35 ± 0.34). An increase was observed for pH (7.41 ± 0.11 vs. 7.72 ± 0.15), Ca (569.09 ± 34 vs. 855 ± 38.17), bulk density (1.17 ± 0.05 vs. 1.66 ± 0.18), the number of arbuscular mycorrhiza (AM) spores, and stump sprouting (1645 ± 533 and 3425 ± 491). Site C showed a similar decrease in organic matter content, N amount, litter depth, germinated seedlings, and earthworm biomass. However, plant diversity was greatly increased at site C, demonstrating that the conditions were better for plant life 8 years after the fire event. Thus, the number of germinated seedlings was lower than that of the control, while stump sprouting (4170 ± 452 per ha) was the greatest. The AM spore count was higher at site B in comparison to site C, indicating that fire had caused a long-term loss in this essential component of the soil. An increase in pH was a characteristic feature of the burnt sites. Levels of macronutrient K were greatly increased at site C. In fact, K content was much higher than the other two sites (A, B, and C: 51.81 ± 3.69, 59.75 ± 8.18, and 72.55 ± 20.66, respectively), indicating that increased K content is a long-term effect of fire. Bulk density (1.80 ± 0.14) increased at site C, which may be due to the insufficient earthworm biomass. Thus, 8 years were not enough to improve the soil conditions for soil fauna. [ABSTRACT FROM AUTHOR]