Divergent plant and nematode community responses to long‐term nitrogen enrichment in a meadow steppe

Abstract Increased nitrogen (N) deposition due to industrial and agricultural activities poses a significant threat to global biodiversity, disrupting ecosystem functions and services. Above‐ and belowground communities are closely interdependent and both respond to N enrichment, yet they are frequently studied separately. Whether the biodiversity of these communities responds similarly or synchronously to N inputs remains underexplored. Using a decade‐long N addition experiment in a meadow steppe ecosystem, we explored the effects of a gradient of N addition levels (from 0 to 50 g N m −2 year −1 ) on the diversity of aboveground plants and belowground nematodes at second, sixth, and tenth years after the initiation of the experiment. Our findings revealed asynchronous responses of above‐ and belowground biodiversity. Plant diversity showed a progressive, time‐dependent decline that intensified with both increasing N concentrations and experimental duration. In contrast, nematode diversity exhibited a threshold response: an initial decline at low N levels (