Nitrogen Pollution Destabilizes Grassland Productivity Above and Below Ground

Nitrogen addition makes grassland plant productivity less stable not only above ground but also below ground, according to a global meta-analysis published in Communications Earth & Environment. The study compiled 542 multi-year observations from 111 studies to assess how added nitrogen affects the temporal stability of net primary productivity, defined as the ratio of temporal mean productivity to its standard deviation over time.

The researchers found that nitrogen addition significantly reduced the stability of both aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP), and that the two declines occurred in a synchronized manner. This coupling, the authors report, reflects an allocation trade-off between the mean values of ANPP and BNPP together with a synchronized increase in their variability, producing parallel losses of stability above and below the soil surface.

The analysis also points to an association with biodiversity. Declines in both ANPP and BNPP stability were linked to decreased plant species richness under nitrogen addition, suggesting that the erosion of temporal productivity on both sides of the ground surface accompanies species loss in these experiments.

The negative responses were not uniform. The destabilizing effect intensified with longer treatment durations and with higher nitrogen addition intensity, indicating that chronic, heavy nitrogen inputs pose the greatest risk to the consistency of grassland productivity over time as captured in the underlying studies.

Because temporal stability of productivity is crucial for sustaining ecosystem services, the authors emphasize that future ecosystem management strategies under global change scenarios should consider above- and below-ground interactions rather than evaluating them in isolation. As a meta-analysis of published multi-year experiments, the study describes average patterns across sites, and the strength of the observed effects depends on treatment duration and nitrogen intensity in the individual studies it synthesized.

Subject of Research: Effects of nitrogen deposition on the coupled stability of aboveground and belowground grassland productivity

Article Title: Coupled responses of aboveground and belowground net primary productivity stability to nitrogen deposition in grasslands

Article References: Zhang, Y., Gao, S., Wang, X., & Liu, H. (2026). Coupled responses of aboveground and belowground net primary productivity stability to nitrogen deposition in grasslands. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-04163-x

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04163-x

Keywords: nitrogen deposition, grasslands, net primary productivity, temporal stability, meta-analysis, aboveground productivity, belowground productivity, species richness, ecosystem services, global change, Coupled, responses