Relative importance between nitrification and denitrification to N₂ O from a global perspective

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Nitrous oxide (N₂ O) is a potent greenhouse gas, and its mitigation is crucial.
• The dominant source of global N₂ O emissions between nitrification and denitrification remains unclear.

Purpose of the Study:

• To determine the primary source of soil N₂ O emissions worldwide.
• To identify the key factors controlling N₂ O production from nitrification and denitrification.

Main Methods:

• Meta-analysis of 1315 soil N₂ O observations from 74 peer-reviewed articles.
• Statistical analysis to identify drivers of N₂ O emission ratios.

Main Results:

• Average N₂ O emissions were higher from nitrification (N₂ O_n) than denitrification (N₂ O_d) globally.
• The ratio of ammonia-oxidizing microorganisms (AOM) to denitrifiers explained 53.7% of the geographical variation in N₂ O_n:N₂ O_d ratios.
• Soil pH significantly influenced N₂ O_n:N₂ O_d ratios in croplands more than in natural ecosystems.

Conclusions:

• Nitrification is the dominant global source of soil N₂ O.
• The AOM:denitrifier ratio is a pivotal driver of N₂ O production.
• Incorporating the AOM:denitrifier ratio into models can improve N₂ O emission predictions for targeted mitigation strategies.