Global patterns of soil gross immobilization of ammonium and nitrate in terrestrial ecosystems

Ahmed S Elrys; Zhaoxiong Chen; Jing Wang; Yves Uwiragiye; Ayman M Helmy; El-Sayed M Desoky; Yi Cheng; Jin-Bo Zhang; Zu-Cong Cai; Christoph Müller

doi:10.1111/gcb.16202

Global patterns of soil gross immobilization of ammonium and nitrate in terrestrial ecosystems

Glob Chang Biol. 2022 Jul;28(14):4472-4488. doi: 10.1111/gcb.16202. Epub 2022 May 2.

Authors

Ahmed S Elrys^{1

2}, Zhaoxiong Chen¹, Jing Wang³, Yves Uwiragiye^{4

5}, Ayman M Helmy², El-Sayed M Desoky⁶, Yi Cheng^{1

7

8}, Jin-Bo Zhang¹, Zu-Cong Cai¹, Christoph Müller^{9

10}

Affiliations

¹ School of Geography, Nanjing Normal University, Nanjing, China.
² Soil Science Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt.
³ College of Forestry, Nanjing Forestry University, Nanjing, China.
⁴ College of Natural Resources and Environment, Northwest A&F University, Yangling, China.
⁵ Department of Agriculture, Faculty of Agriculture, Environmental Management and Renewable Energy, University of Technology and Arts of Byumba, Byumba, Rwanda.
⁶ Botany Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt.
⁷ Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, China.
⁸ Jiangsu Engineering Research Center for Soil Utilization & Sustainable Agriculture, Nanjing, China.
⁹ Institute of Plant Ecology, Justus Liebig University Giessen, Giessen, Germany.
¹⁰ School of Biology and Environmental Science and Earth Institute, University College Dublin, Dublin, Ireland.

PMID: 35445472
DOI: 10.1111/gcb.16202

Abstract

Microbial nitrogen (N) immobilization, which typically results in soil N retention but based on the balance of gross N immobilization over gross N production, affects the fate of the anthropogenic reactive N. However, global patterns and drivers of soil gross immobilization of ammonium (I_NH4 ) and nitrate (I_NO3 ) are still only tentatively known. Here, we provide a comprehensive analysis considering gross N production rates, soil properties, and climate and their interactions for a deeper understanding of the patterns and drivers of I_NH4 and I_NO3 . By compiling and analyzing 1966 observations from 274 ¹⁵ N-labelled studies, we found a global average of I_NH4 and I_NO3 of 7.41 ± 0.72 and 2.03 ± 0.30 mg N kg^-1 day^-1 with a ratio of I_NO3 to I_NH4 (I_NO3 :I_NH4 ) of 0.79 ± 0.11. Soil I_NH4 and I_NO3 increased with increasing soil gross N mineralization (GNM) and nitrification (GN), microbial biomass, organic carbon, and total N and decreasing soil bulk density. Our analysis revealed that GNM and GN were the main stimulators for I_NH4 and I_NO3 , respectively. The structural equation modeling showed that higher soil microbial biomass, total N, pH, and precipitation stimulate I_NH4 and I_NO3 through enhancing GNM and GN. However, higher temperature and soil bulk density suppress I_NH4 and I_NO3 by reducing microbial biomass and total N. Soil I_NH4 varied with terrestrial ecosystems, being greater in grasslands and forests, which have higher rates of GNM, than in croplands. The highest I_NO3 :I_NH4 was observed in croplands, which had higher rates of GN. The global average of GN to I_NH4 was 2.86 ± 0.31, manifesting a high potential risk of N loss. We highlight that anthropogenic activities that influence soil properties and gross N production rates likely interact with future climate changes and land uses to affect soil N immobilization and, eventually, the fate of the anthropogenic reactive N.

Keywords: 15N isotopic pool dilution technique; climate; land use change; microbial biomass; soil N retention; soil properties.

MeSH terms

Ammonium Compounds*
Ecosystem
Nitrates
Nitrogen / analysis
Nitrogen Oxides
Soil Microbiology
Soil* / chemistry

Substances

Ammonium Compounds
Nitrates
Nitrogen Oxides
Soil
Nitrogen