Cumulative and partially recoverable impacts of nitrogen addition on a temperate steppe

Atmospheric nitrogen (N) deposition has been shown to decrease biodiversity and change nutrient cycles in terrestrial ecosystems. However, our understanding of ecological responses to chronic N addition and ecological recovery from N enrichment to grassland is limited. Here we present evidence from an 11-year grassland experiment with a range of N addition rates (0, 30, 60, 120, 240, and 480 kg N ha−1 yr−1) in Inner Mongolia, China. Chronic N addition led to a reduction in species richness, Shannon Diversity Index and soil pH, and an increase in aboveground biomass, foliar N and soil mineral N. High N addition rates (240 and 480 kg N ha−1 yr−1) showed significant effects in the first and second years, which stabilized over time. Nitrogen addition at low rates (30 and 60 kg N ha−1 yr−1) took longer (e.g., ≥ 3 years) to achieve significant effects. The negative impacts of high N addition (480 kg N ha−1 yr−1) were reduced and species richness, etc., showed a limited but rapid recovery with...