Atmospheric nitrogen (N) deposition generally reduces the temporal stability of plant communities (community stability). The positive community stability–area relationship (CSAR) has been reported, but the effects of N deposition on CSAR are unexplored, particularly given that plant N absorption rhythm links with seasonal N enrichment.

By conducting an experiment with N additions during autumn, winter, or the growing season in a temperate grassland, we employed the first 6 years' nested plant survey over 0.01–16 m2 to explore the influence on CSAR.

We found that community stability still increased with area under N addition. Seasonal N additions reduced community stability at the local scale (i.e. CSAR intercepts), while N addition in winter or the growing season, but not autumn, reduced CSAR slopes. Moreover, N additions altered the slopes of the relationships between species diversity, species asynchrony, and population stability and area, though the effects varied in magnitude among seasonal inputs. Partial regressions revealed that species diversity exerted stronger pure effects (average about four times in R2) on stability than area. This benefit was attributed to increased species asynchrony and population stability, even with N-enriched conditions.

Our research showed distinct degrees of influence of seasonal N addition on community stability across scales, highlighting that coupling seasonality and spatial scales is warranted for preserving biodiversity to maintain natural ecosystems under N deposition scenarios.