Do plants directly absorb nitrogen derived from deposition of wildfire smoke?

Biomass burning generates a substantial amount of smoke through high-energy combustion. This smoke is deposited into forest ecosystems either as aerosol smoke or as smoke-laden water in rainfall. The smoke contains essential elements like nitrogen (N) and other elements essential for plant growth and development. However, it is not well understood whether plant roots directly absorb the wildfire-derived N. An understanding of such a phenomenon is of significant importance in revealing the impact of forest fires on N input into forest ecosystems. Thus, this study examined the effects of different smoke concentrations on total N content in the soil and δ15N in plant and biomass production of Cunninghamia lanceolata seedlings under different cultivation methods using the 15N tracing technique. The main findings showed that smoke at a certain concentration had a promoting effect on plant growth, and the contribution of fire wildfire-derived 15N to soil total N was higher in low concentration smoke treatment than high concentration. After 180 days of cultivation, the wildfire-derived 15N content of various plant organs was higher for low than high smoke concentration treatment, and the content being higher for fine roots, where N absorption was enhanced in aeroponics-cultivated than soil-cultivated seedlings. The study demonstrated that plant roots directly absorb N from smoke and transported it to the aboveground parts for internal circulation. The effect of smoke on plant growth was concentration-dependent, with high concentration of smoke inhibiting plant growth compared to the control, while low concentration stimulated growth. The findings emphasize that smoke generated from low-intensity fires can have a positive impact on unburnt patches within the footprint of a fire through N deposition.