Additive negative effects of decadal warming and nitrogen addition on grassland community stability

Much recent research has explored how global warming and increased nitrogen (N) deposition, two important components of global environmental changes, influence the structure and functioning of natural ecosystems. However, how ecosystem dynamics respond to the combination of long-term warming and N enrichment remains largely unexplored. We investigated the impact of warming and N addition on the temporal stability of plant communities in a decade-long field experiment, conducted in a desert steppe in northern China, using a split-plot design with warming as the main-plot factor and N addition as the split-plot factor. Long-term warming and N addition had additive, negative effects on plant community stability. A warming-induced decrease in species richness was not a significant driver of decreased community stability, which was instead driven by the decreased stability of dominant species under warming. On the other hand, a N-induced decrease in community stability was ascribed to both decreased stability of dominant and common species and decreased asynchronous population dynamics under N addition. Synthesis. Our results suggest that ongoing anthropogenic environmental changes may have appreciable consequences for the stability of natural grassland functions and services while also highlighting the different mechanisms associated with the similar effects of climate warming and increased N deposition on grassland community stability.