Title

Relative importance between nitrification and denitrification to N2O from a global perspective

Athour

Bingbing Han, Yanzhong Yao, Bin Liu ,Yini Wang, Xiaoxuan Su, Lihua Ma, Dunyi Liu, Shuli Niu, Xinping Chen, Zhaolei Li *

Corresponding author: Zhaolei Li, Professor

E-mail: lizhaolei@swu.edu.cn

Correspondence address: College of Resources and Environment, and Academy of Agricultural Sciences, Southwest University, Chongqing 400715, China

Data abstract

Nitrous oxide (N2O) is a potent green-house gas and its mitigation is a pressing task in the coming decade. However, it remains unclear which specific process between concurrent nitrification and denitrification dominates worldwide N2O emission. We snagged an opportunity to ascertain whence the N2O came and which were the controlling factors on the basis of 1315 soil N2O observations from 74 peer-reviewed articles. The average N2O emission derived from nitrification (N2On) was higher than that from denitrification (N2Od) worldwide. The ratios of nitrification-derived N2O to denitrification-derived N2O, hereof N2On:N2Od, exhibited large variations across terrestrial ecosystems.** **Although soil carbon and nitrogen content, pH, moisture, and clay content accounted for a part of the geographical variations in the N2On:N2Od ratio, ammonia-oxidizing microorganisms (AOM):denitrifier ratio was the pivotal driver for the N2On:N2Od ratios, since the AOM:denitrfier ratio accounted for 53.7% of geographical variations in N2On:N2Od ratios. Compared with natural ecosystems, soil pH exerted a more remarkable role to dictate the N2On:N2Od ratio in croplands. This study emphasizes the vital role of functional soil microorganisms in geographical variations of N2On:N2Od ratio, and lays the foundation for the incorporation of soil AOM:denitrfier ratio into models to better predict N2On:N2Od ratio. Identifying soil N2O derivation will provide a global potential benchmark for N2O mitigation by manipulating the nitrification or denitrification.

Data collect

The data were collected from published peer-reviewed papers obtained from two libraries: Web of Science (https://apps.webofknowledge.com) and China National Knowledge Infrastructure Database (https://www.cnki.net). The string of keywords for surveying the papers was ‘soil AND nitrification AND denitrification AND N2O’. Additional papers were supplemented using Google Scholar. The publication time for the papers was up to July 1, 2022. Initially, 1009 papers were gotten (323 papers in Chinese and 686 papers in English), and the dataset was compiled following the guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Data-Analyses; Fig. S1). The criteria for screening papers were: 1. The N2On and N2Od were measured. 2. The topsoil were used to measure N2O emission (e.g., soil depth was top 0-30 cm). Data from the soil profile were excluded as it is sporadic. Accordingly, 74 studies met the criteria, in which 56 studies came from laboratory incubation and 18 studies came from field experiment. We compared the N2On, N2Od, and N2On:N2Od ratio between laboratory incubation and field experiment using t-test, and no significant differences were observed in N2On, N2Od, and N2On:N2Od ratio between laboratory incubation and field experiment (all p > 0.05; Figure S2).

Notably, there are some empty cells in the dataset, indicating that there were no values or missing values, i.e., NA. To make it easier to run R (version4.2.2.) we don't fill the null value with NA or Null. In sheet2 (i.e., the Readme) of the uploaded dataset, we provide the specific meaning of each heading and its unit of expression. The details of experimental site were also extracted from papers, including the geographic information of experiment site (i.e., latitude and longitude), climate conditions (i.e., mean annual temperature (MAT) and mean annual precipitation (MAP)) and ecosystem types (i.e., grasslands, forests and croplands). Additionally, soil physicochemical properties [soil pH, the ratio of carbon to nitrogen (soil C:N), total nitrogen (TN), bulk density (BD), clay content and ammonium content (NH4+), nitrate (NO3-), soil moisture (WHC%), Nitrification-derived N2O (N2On), Denitrification-derived N2O (N2Od), Percentage of nitrification-derived N2O (N2On proportion), Percentage of denitrification-derived N2O (N2Od proportion), AOA (ammonia-oxidizing archaea), AOB (ammonia-oxidizing bacteria), nirS (S type nitrite reductase), and nirK (K type nitrite reductase)]. 

Data processing software

We processed the entire set of data by utilizing the R language, version4.2.2., R Core Team.

Contact Information

Corresponding author: Zhaolei Li, Professor

E-mail: lizhaolei@swu.edu.cn

ORCID: https://orcid.org/0000-0001-8767-1277