Nitrogen Dynamics and Cycling in Terrestrial Ecosystems

Nitrogen is a fundamental element governing productivity, biodiversity and biogeochemical feedbacks in terrestrial ecosystems. In soils, nitrogen occurs in multiple forms—from atmospheric N₂ fixed by specialised microorganisms to inorganic ammonium and nitrate, and complex organic compounds within soil organic matter. Microbial processes such as mineralisation, nitrification and denitrification interconvert these pools, mediating plant-available nitrogen and gaseous losses to the atmosphere. Biological fixation and atmospheric deposition supply new reactive nitrogen, while leaching, runoff and gaseous emissions remove it. Agricultural intensification and fossil fuel combustion have more than doubled the flux of reactive nitrogen globally, driving eutrophication of water bodies, altering forest health and influencing carbon sequestration. In grasslands and croplands, fertilisation regimes affect soil organic carbon stocks and biodiversity, whereas in forest canopies and deep soil horizons, unexpected microbial activity can transform or release long-buried carbon. Understanding the spatial and temporal coordination of nitrogen transformations—from the leaf surface to metre-deep soil layers—is essential for managing nutrient cycling, mitigating greenhouse-gas emissions and sustaining ecosystem services under global change.

Research from Nature Portfolio

Recent meta-analysis of over 500 grassland and cropland experiments demonstrates that organic fertilisation increases aboveground biomass by more than 50% while enhancing plant diversity and soil organic carbon, in contrast to inorganic fertilisers which often reduce diversity. The positive effects of organic amendments on soil carbon build-up are most pronounced in warmer grassland regions. In parallel, studies in temperate forests reveal that up to 80% of nitrate entering soils derives from microbial nitrification on leaf surfaces. Autotrophic nitrifiers inhabiting canopy foliage convert deposited ammonium into nitrate, significantly altering throughfall chemistry and influencing soil nitrogen inputs beneath forest stands. These findings highlight the dual importance of fertilisation strategy and canopy-based microbial transformations in shaping terrestrial nitrogen retention and fluxes.

Nitrogen Dynamics and Cycling in Terrestrial Ecosystems publication trend

The graph below shows the total number of articles in nitrogen dynamics and cycling in terrestrial ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Mineralisation: Microbial conversion of organic nitrogen into inorganic ammonium.

Nitrification: Two-step microbial oxidation of ammonium to nitrate.

Denitrification: Microbial reduction of nitrate to gaseous nitrogen oxides or N₂, removing reactive nitrogen from soil.

Reactive nitrogen: All biologically, photochemically or radiatively active nitrogen species excluding N₂.

Depolymerisation: Enzymatic breakdown of large organic nitrogen compounds into simpler forms accessible to microbes and plants.

Canopy nitrification: Oxidation of deposited ammonium to nitrate by microorganisms residing on leaf surfaces.

References

1. A global meta-analysis on the effects of organic and inorganic fertilization on grasslands and croplands. Nature Communications (2024).
2. Substantial contribution of tree canopy nitrifiers to nitrogen fluxes in European forests. Nature Geoscience (2024).
3. Anthropogenic N input increases global warming potential by awakening the “sleeping” ancient C in deep critical zones. Science Advances (2023).
4. Expression of macromolecular organic nitrogen degrading enzymes identifies potential mediators of soil organic N availability to an annual grass. The ISME Journal: Multidisciplinary Journal of Microbial Ecology (2023).