The gap between atmospheric nitrogen deposition experiments and reality

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Authors

Daniel Patrick Bebber

Abstract

Anthropogenic activities have dramatically altered the global nitrogen (N) cycle. Atmospheric N deposition, primarily from combustion of biomass and fossil fuels, has caused acidification of precipitation and freshwater and triggered intense research into ecosystem responses to this pollutant. Experimental simulations of N deposition have been the main scientific tool to understand ecosystem responses, revealing dramatic impacts on soil microbes, plants, and higher trophic levels. However, comparison of the experimental treatments applied in the vast majority of studies with observational and modelled N deposition reveals a wide gulf between research and reality. While the majority of experimental treatments exceed 100 kg N ha-1 y-1, global median land surface deposition rates are only around 1 kg N ha-1 y-1 and only exceed 10 kg N ha-1 y-1 in certain regions, primarily in China. Experimental N deposition treatments are in fact similar to mineral fertilizer application rates in agriculture. Some ecological guilds, such as saprotrophic fungi, are highly sensitive to N and respond differently to low and high N availability. In addition, very high levels of N application cause changes in soil chemistry, such as acidification, meaning that unrealistic experimental treatments are unlikely to reveal true ecosystem responses to N. Hence, despite decades of research, past experiments can tell us little about how the biosphere has responded to anthropogenic N deposition. A new, and more realistic, approach is required if experimental studies are to contribute to our understanding of this important phenomenon.

DOI

https://doi.org/10.31223/X5X89Z

Subjects

Agricultural Science, Agriculture, Atmospheric Sciences, Biogeochemistry, Environmental Indicators and Impact Assessment, Environmental Microbiology and Microbial Ecology Life Sciences, Environmental Monitoring, Forest Biology, Other Environmental Sciences, Planetary Biogeochemistry, Soil Science, Terrestrial and Aquatic Ecology

Keywords

nitrogen deposition, ammonia, nitrate, nitrogen cycle, meta-analysis, critical load, experimental design

Dates

Published: 2021-05-05 10:15

Last Updated: 2021-05-05 14:16

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License

CC BY Attribution 4.0 International

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Conflict of interest statement:
None

Data Availability (Reason not available):
None

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