Fraction of nitrous oxide production in nitrification and its effect on total soil emission: A meta-analysis and global-scale sensitivity analysis using a process-based model

Abstract

Nitrification in terrestrial soils is one of the major processes of emission of nitrous oxide (N 2 O), a potent greenhouse gas and stratospheric-ozone-depleting substance. We assessed the fraction of N 2 O emission associated with nitrification in soil through a meta-analysis and sensitivity analysis using a process-based model. We corrected observational values of gross nitrification and associated N 2 O emission rates from 71 records for various soils in the world spanning from 0.006% to 29.5%. We obtained a median value of 0.14%, and then assessed how the nitrification-associated N 2 O emission fraction has been considered in terrestrial nitrogen cycle models. Using a process-based biogeochemical model, we conducted a series of sensitivity analyses for the effects of different values of nitrification-associated N 2 O emission fraction on soil N 2 O emission. Using an empirical relationship between soil pH and nitrification-associated N 2 O emission fraction, the model well simulated global emission patterns (global total in the 2000s, 16.8 Tg N 2 O yr –1 ). Differences in the nitrification-associated N 2 O emission fraction caused differences in total N 2 O emission of as much as 2.5 Tg N 2 O yr –1 . Therefore, to obtain reliable estimation of soil N 2 O emission for nitrogen and climate management, it is important to constrain the parameterization in models by ensuring extensive and accurate observations.

Influence of Tillage Systems, and Forms and Rates of Nitrogen Fertilizers on CO2 and N2O Fluxes from Winter Wheat Cultivation in Oklahoma

“…The first three months during flux measurements were dry, with only 53 mm precipitation received during October through December 2016. Therefore, soil conditions were not conducive for denitrification, a major microbial pathway for N 2 O production in the soil [32]. Although frequent large precipitation events occurred in February and April, emissions did not increase during that time period.…”

What can we learn from N2O isotope data? – Analytics, processes and modelling

“…Moving one step up on the spatiotemporal scale, considering the variety of pathways contributing to N 2 O production and consumption at site to regional scales has revealed the importance of spatiotemporal heterogeneity as well as non‐linear responses to the drivers at work. For example, soil moisture is a key parameter regulating N 2 O emission pathways, and is often used in models as the primary driver of N‐gas emissions 76,77 . Although these simple parameterization methods provide the first step in constraining emission processes, recent results highlight the importance of also considering other drivers in these models, such as pH regulation of nitrification 77 and N 2 O reduction, microbial biomass and land use history, and substrate mobilization and availability 36,78 .…”

“…For example, soil moisture is a key parameter regulating N 2 O emission pathways, and is often used in models as the primary driver of N‐gas emissions 76,77 . Although these simple parameterization methods provide the first step in constraining emission processes, recent results highlight the importance of also considering other drivers in these models, such as pH regulation of nitrification 77 and N 2 O reduction, microbial biomass and land use history, and substrate mobilization and availability 36,78 . The N 2 O emissions during “hot moments” and from “hot spots” in the environment are also increasingly recognized as playing a major role in annual and regional N 2 O budgets, but their controls are particularly challenging to understand in their full complexity, and thus difficult to model 79–82 .…”

In silico assessment of the potential of basalt amendments to reduce N2O emissions from bioenergy crops

“…However, the model does not integrate regulating functions of soil pH on denitrification, the accuracy of simulated N 2 O emissions relaying on single point calibrations against fixed soil pH values. Given that denitrification is the predominant N 2 O‐producing process at the global scale (Davidson, 2009; Inatomi et al, 2019; Xu‐Ri et al., 2012), failing to adequately capture the dynamic interaction of soil pH and the denitrification metabolism could result in strong biases in N 2 O flux estimates over a wide range of soil pH, both spatially and over time. Prior to using the model to explore the effects of basalt addition on N 2 O fluxes, it was modified to incorporate soil pH interactions with the total activity and end‐product stoichiometry of denitrification by coupling pH with pre‐existing denitrification functions.…”