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.