Data from: 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 the cessation of N addition. Our findings suggest serious and cumulative impacts of N addition on plant and soil communities but the potential for partial system recovery over time if N inputs decline or cease.

大气氮（N）沉降已被证实会降低陆地生态系统的生物多样性，并改变其养分循环。然而，目前学界对长期氮添加的生态响应，以及草地生态系统从氮富集状态中恢复的过程仍缺乏充分认知。本研究基于中国内蒙古地区一项为期11年的草地控制实验，设置了梯度氮添加处理（添加量分别为0、30、60、120、240及480 kg N ha⁻¹ yr⁻¹），并据此提供相关实验证据。长期氮添加会降低群落物种丰富度、香农多样性指数（Shannon Diversity Index）及土壤pH值，同时提升地上生物量、植物叶片氮含量与土壤矿质氮含量。高剂量氮添加处理（240和480 kg N ha⁻¹ yr⁻¹）在实验前两年即显现出显著影响，且该影响随实验时长推移趋于稳定。低剂量氮添加处理（30和60 kg N ha⁻¹ yr⁻¹）则需要更长时间（如≥3年）才能产生显著生态效应。当停止氮添加后，高剂量处理组（480 kg N ha⁻¹ yr⁻¹）的负面生态影响有所缓解，物种丰富度等指标呈现出有限但快速的恢复态势。本研究结果表明，氮添加对植物与土壤群落存在显著且累积的负面影响，但如果氮输入量下降或完全停止，生态系统具备部分恢复的潜在可能。