Dataset for shifting long term N impacts on plant productivity

Although some long-term studies have been conducted to quantify nitrogen (N) impacts on plant productivity, uncertainties remain regarding whether these impacts change over time and the underlying mechanisms. By overlooking this, we may over- or under-estimate N impacts on terrestrial ecosystems. Our goal was to determine whether N impacts on plant productivity change in the long term and the controls. We synthesized 63 N addition studies with duration ≥ 8 years in natural terrestrial ecosystems. Our results show shifting temporal N impacts on plant productivity in terrestrial ecosystems, and the direction of this change varies with biome type (forests: decrease; grasslands and shrublands: increase). The temporal pattern of N impacts is mostly regulated by mean annual precipitation (MAP), mean annual temperature (MAT), and initial soil pH, which account for 24%, 19%, and 19% of the variation, respectively. Our findings indicate that temporally dynamic impacts of long-term N addition on plant productivity is generally observed among studies in terrestrial ecosystems, and climate variables shape the temporal pattern of long-term N impacts on plant productivity. Therefore, not only the magnitude of N impacts on plant productivity, but also their temporal dynamics, should be considered in future experimental and model research.

尽管已有多项长期研究量化了氮（Nitrogen）对植物生产力的影响，但关于此类影响是否会随时间发生变化，以及其背后的潜在机制，仍存在诸多不确定性。若忽略此类不确定性，我们可能会高估或低估氮对陆地生态系统的影响。本研究旨在明确氮对植物生产力的影响是否会在长期尺度上发生变化，及其调控因子。我们整合了63项在自然陆地生态系统中开展、时长≥8年的氮添加实验研究。研究结果表明，陆地生态系统中氮对植物生产力的影响随时间呈现动态变化，且这一变化的方向因生物群系（biome）类型而异：森林生态系统中该影响呈下降趋势，草地与灌丛生态系统中则呈上升趋势。氮影响的时间动态模式主要受年平均降水量（Mean Annual Precipitation, MAP）、年平均气温（Mean Annual Temperature, MAT）以及初始土壤pH值调控，三者分别解释了24%、19%与19%的变异量。本研究结果显示，在陆地生态系统的相关研究中，长期氮添加对植物生产力的动态影响普遍存在，且气候变量会塑造长期氮添加对植物生产力影响的时间动态模式。因此，在未来的实验与模型研究中，不仅需要考量氮对植物生产力影响的强度，还应兼顾其时间动态特征。