Nitrogen Enhancement Effects on Soil Carbon Dynamics

Nitrogen enrichment, whether through atmospheric deposition or fertiliser application, exerts a multifaceted influence on the cycling and storage of soil organic carbon (SOC). Enhanced nitrogen availability often stimulates plant growth and litter inputs, thereby increasing the input of organic substrates to soil. At the same time, shifts in microbial community composition and enzyme activities can accelerate or suppress the decomposition of different SOC fractions. Key components of the SOC pool—particulate organic carbon (POC) and mineral-associated organic carbon (MAOC)—respond in distinct ways: POC tends to increase more rapidly under nitrogen addition, reflecting higher plant biomass returns, while gains in MAOC are more modest and depend on microbial processing and physicochemical protection. Depth-dependent responses further complicate predictions, as topsoils may accumulate carbon with short-term nitrogen inputs whereas subsoils exhibit delayed or even negative responses over time. Ecosystem type, experimental duration and soil properties such as pH and texture modulate these patterns, revealing both opportunities for enhanced carbon sequestration and risks of reduced stability of the SOC pool under chronic nitrogen enrichment. Understanding these interactions is critical for forecasting terrestrial carbon sinks in a world of rising nitrogen deposition and for designing management strategies that harness nitrogen inputs to mitigate climate change.

Research from Nature Portfolio

A comprehensive meta-analysis synthesising data from multiple ecosystems demonstrated that experimental nitrogen addition increased soil total carbon storage globally by approximately 5.8%. Above- and below-ground plant carbon contents rose by more than 25% and 16%, respectively, driving higher inputs of litter and root biomass. Despite these increases, the flux of carbon through decomposition and soil respiration remained largely unchanged, suggesting that enhanced plant productivity rather than slowed mineralisation underpins the observed carbon gains. Overall, this work indicates that nitrogen inputs can bolster soil carbon pools across terrestrial biomes, reinforcing the potential role of nitrogen deposition in strengthening ecosystem carbon sinks.

Nitrogen Enhancement Effects on Soil Carbon Dynamics publication trend

The graph below shows the total number of articles in nitrogen enhancement effects on soil carbon dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Soil organic carbon (SOC): Total carbon stored in soil as decomposed plant and microbial residues.

Particulate organic carbon (POC): Coarse, unprotected organic matter derived chiefly from plant detritus.

Mineral-associated organic carbon (MAOC): Organic compounds bound to soil minerals, conferring greater stability and longer turnover times.

Carbon use efficiency (CUE): Ratio of microbial biomass carbon produced to total carbon assimilated, indicating the efficiency of microbial growth.

Microbial necromass: Remains of dead microbial cells that contribute to stable soil carbon pools.

References

1. Stimulation of terrestrial ecosystem carbon storage by nitrogen addition: a meta-analysis. Scientific Reports (2016).
2. Depth‐dependent responses of soil organic carbon under nitrogen deposition. Global Change Biology (2024).
3. Progress on the Effect of Nitrogen on Transformation of Soil Organic Carbon. Processes (2022).
4. Nitrogen addition effects on soil mineral-associated carbon differ between the valley and slope in a subtropical karst forest. Geoderma (2023).