Rare species facilitate partial recovery of plant diversity after decade-long nitrogen addition

Community diversity exhibits partial recovery following the cessation of nitrogen (N) addition, yet the underlying mechanisms remain insufficiently understood. In this study, we examined the short-term responses of plant communities and environmental factors to N cessation in an alpine meadow on the eastern Qinghai-Tibetan Plateau after a decade-long period of N addition. Our study reveals a transient window of opportunity for the resurgence of rare species following N cessation. This recovery of rare species was the primary driver of the observed increase in plant species diversity. During this temporary phase, increased light availability and reduced soil nutrient (nitrogen and phosphorus) levels disrupted historical competitive hierarchies by enhancing the performance of rare species while weakening dominant species. These findings offer novel insights into community reassembly under nutrient enrichment stress and highlight the potential for short-term, targeted interventions to facilitate near-natural restoration, providing valuable guidance for ecosystem management and biodiversity conservation in grassland ecosystems.