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 (<10 g N m −2 year −1 ) followed by stabilization across higher N concentrations, with no significant temporal intensification of this pattern over the course of the decade‐long study. Plant richness declined primarily due to rapid species loss, especially among forbs, with little compensatory gain. In contrast, nematode diversity exhibited a more balanced response, driven by species replacements in which gains offset losses. Bacterivores and omnivores‐predators were the most negatively affected nematode groups. This study advances our understanding of ecological responses to nitrogen enrichment by revealing the contrasting long‐term dynamics of above‐ and belowground communities in a meadow steppe ecosystem. While plant diversity deteriorates with increased N input, nematode diversity shows signs of resilience via compensatory turnover, highlighting the potential for belowground biota to buffer ecosystem‐level biodiversity loss under chronic N deposition. Our findings underscore the critical need to consider both plant and soil biota simultaneously when assessing the impacts of N deposition on biodiversity.
Lu et al. (Thu,) studied this question.