A relative method for measuring nitric oxide (NO) fluxes from forest soils

Area of Science:

• Environmental Science
• Soil Science
• Atmospheric Chemistry

Background:

• Forest ecosystems globally face high nitrogen (N) deposition.
• Nitrogen deposition contributes to atmospheric nitric oxide (NO) emissions, impacting tropospheric oxidative capacity.
• Traditional methods for measuring NO flux in forests are labor-intensive and require power.

Purpose of the Study:

• To develop a more accessible method for measuring soil nitric oxide (NO) fluxes in forest ecosystems.
• To validate a novel relative method based on Fick's law of diffusion for NO flux quantification.
• To assess the method's applicability in N-saturated forest soils.

Main Methods:

• Developed a relative measurement method for NO fluxes based on Fick's law of diffusion.
• Utilized relationships between NO, N₂O, and CO₂ fluxes and their soil-atmosphere concentration gradients.
• Conducted laboratory and field experiments using soil from a subtropical forest in China.

Main Results:

• The relative method, particularly the form based on equilibrium gas at the soil water surface, showed good agreement with the traditional chamber method.
• Deviation rates between the new method and the chamber method were approximately 9% and 30% for the two forms tested.
• The method demonstrated applicability in measuring NO fluxes from N-saturated forest soils.

Conclusions:

• The developed relative method offers a robust approach for measuring NO fluxes in forest soils, especially in N-saturated environments.
• This method is particularly useful where traditional dynamic chamber methods are impractical due to power limitations.
• The findings contribute to a better understanding of NO flux variations and improve nitrogen budgeting in global forest ecosystems.