Intra-annual species gain overrides species loss in determining species richness in a typical steppe ecosystem after a decade of nitrogen enrichment

Increasing deposition of atmospheric nitrogen (N) due to accelerated human activities is a threat to various ecosystems. However, there is a lack of long-term experimental evidence demonstrating the seasonal dynamics of plant species turnover that ultimately determine species richness in natural ecosystems under N enrichment. Moreover, the frequency of N addition also may affect species turnover in a community, but it is rarely studied.
To assess the responses of a plant community to N addition, we manipulated the amounts (0-50 g N m-2 year-1) and frequency (2 vs. 12 times year-1) of N addition in an Inner Mongolian typical steppe ecosystem in northern China for 12 consecutive years (2008-2020). We measured species richness and density of plant in the growing seasons (May-September) from 2018 to 2020, starting 10 years after the initial N addition treatment.
Both species gain and species loss decreased with increasing amounts of N addition, resulting in a lower plant species turnover ra...

人类活动加剧导致大气氮（N）沉降持续增加，对各类生态系统构成威胁。然而，目前尚缺乏长期实验证据，可阐明氮富集条件下自然生态系统中最终决定物种丰富度的植物物种周转（species turnover）的季节动态。此外，氮添加（N addition）频率或许会影响群落内的物种周转，但相关研究尚属罕见。为探究植物群落对氮添加（N addition）的响应，我们在中国北方内蒙古典型草原生态系统中开展了为期12年（2008-2020年）的野外控制实验，设置了0~50 g N·m⁻²·年⁻¹的氮添加剂量梯度与2次·年⁻¹、12次·年⁻¹两种氮添加频率。本研究于初始氮添加处理实施10年后的2018-2020年的生长季（5-9月），测定了植物物种丰富度与植株密度。随着氮添加剂量升高，物种迁入与物种消亡均呈下降趋势，最终导致植物物种周转速率[原文未完整]