Microbial Potential for Ecosystem N Loss Is Increased by Experimental N Deposition

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Soil science

Background:

• Anthropogenic nitrogen (N) inputs are rising due to fossil fuel combustion and fertilizer use.
• The impact of increased N on soil microbial N cycling mechanisms is not fully understood.

Purpose of the Study:

• To investigate the long-term effects of experimental nitrogen deposition on the soil microbial community's genetic potential for N cycling.
• To assess how N deposition influences genes related to N loss versus N input and retention.

Main Methods:

• Shotgun metagenomics was employed on a long-term field experiment with replicated plots.
• Analysis focused on the genetic potential of soil microbial communities after two decades of N deposition.

Main Results:

• Experimental N deposition significantly increased microbial genes involved in N loss pathways (denitrification and nitrification).
• Genes associated with N input (N fixation) and retention (microbial N assimilation) showed less positive responses.
• Microbial taxa and genes for essential functions like DNA replication remained unaffected.

Conclusions:

• Two decades of N deposition favored genetic pathways promoting ecosystem N loss.
• This suggests a potential genetic mechanism for increased N loss as anthropogenic N deposition continues to rise.