Effects of Forest Fire Smoke Deposition on Soil Physico-Chemical Properties and Bacterial Community

The number of forest fires has increased globally, together with considerable smoke emission that significantly impacts the atmospheric environment and associated ecosystems. Most current studies have focused on the in situ effects of fire on the forest ecosystem. However, the mechanisms by which smoke pollutants impact adjacent ecosystems are rarely reported. In this study, a combustion device and a simulation system were developed to evaluate the effect of forest fire smoke on soil physico-chemical properties of adjacent farmland. The abundance and diversity of bacterial community were also determined. The smoke treatments were control, smoke derived from low and high litter mass.The results showed that smoke deposition increased the contents of total carbon (TC), total nitrogen (TN), and total phosphorus (TP) in the 0–10 cm soil layer; however, no significant changes in soil water content (SWC) and pH values was observed. The ACE and Chao1 indices generally showed a downward trend whereas the PD_whole_ tree index increased after 180 d of smoke deposition. The relative abundance of Proteobacteria remained stable, and Firmicutes in soil decreased after 180 d of smoke deposition. Smoke deposition only slightly affected the physical and chemical properties of the 10–20 cm soil, but the range of variation of dominant bacteria exceeded that of the 0–10 cm soil. A significant positive correlation was found between the soil properties and the alpha diversity indices during the first 30 d after smoke deposition; the correlation then decreased gradually. Redundancy analysis revealed that Proteobacteria, Firmicutes, and Actinobacteria were generally positively correlated with TC, TN, and SWC. As a whole, the study reveals that the effects of smoke deposition on soil physico-chemical properties and bacterial community depends on smoke concentration where relatively low concentration appears to be beneficial to soil bacterial community