Disentangling gross N₂O production and consumption in soil

Area of Science:

• Soil Science
• Environmental Science
• Biogeochemistry

Background:

• Accurate measurement of soil nitrous oxide (N₂O) production and consumption is crucial for predicting its atmospheric dynamics.
• Existing methods for quantifying gross N₂O fluxes present challenges in disentangling production and consumption processes.

Purpose of the Study:

• To compare the gas-flow soil core (GFSC) and ¹⁵N₂O pool dilution (¹⁵N₂OPD) methods for measuring gross N₂O fluxes in various soil types.
• To propose distinct terminology for the fluxes measured by each method to improve clarity in N₂O research.

Main Methods:

• Intact soil cores were collected from grassland, cropland, beech, and pine forests.
• Measurements of gross N₂O production and consumption were performed using both GFSC and ¹⁵N₂OPD techniques.
• ¹⁵N₂O pool dilution involved adding ¹⁵N₂O to the chamber headspace and monitoring isotopic dilution over time.

Main Results:

• Gross N₂O production and consumption measured by ¹⁵N₂OPD were substantially lower (10% and 6%, respectively) than those measured by GFSC across all sites.
• The ¹⁵N₂OPD method is uniquely capable of measuring atmospheric N₂O uptake in soils under field conditions.
• Significant discrepancies highlight the need for method-specific interpretations of N₂O flux data.

Conclusions:

• The GFSC and ¹⁵N₂OPD methods quantify different aspects of soil N₂O dynamics.
• The study recommends using 'gross N₂O emission and uptake' for ¹⁵N₂OPD and 'gross N₂O production and consumption' for GFSC to avoid confusion.
• Clearer terminology will enhance the understanding and prediction of soil N₂O budgets and their role in the soil-atmosphere interface.