Plant phenology response to nitrogen addition decreases community biomass stability in an alpine meadow

Abstract

• Phenology is a sensitive indicator of plant responses to environmental changes, and its shifts could impact community structure and function. However, the effects of phenological shifts on community stability are poorly understood.
• We conducted a 4-yr N enrichment and precipitation change experiment to assess their effects on community stability through phenological responses. To do so, we measured phenological duration and overlap (based on leaf-out and flowering phenology of 55 species) in an alpine meadow on the Tibetan Plateau.
• N enrichment extended the vegetative stage of grasses, sedges, and community by 4.62, 4.72, and 11.74 d, respectively, but shortened that of forbs by 6.14 d and increased the overlap of flowering among individuals within the community. Meanwhile, N enrichment decreased species richness, asynchrony, and stability of sedges. Furthermore, N enrichment decreased community stability by decreasing asynchrony but was not associated with richness. Interestingly, N enrichment also decreased sedges stability by extending their vegetative stage and increasing the overlap of flowering, consequently reducing community stability.
• Our findings imply that N enrichment reduces phenological compensation and thus threatens grassland stability, which highlights the importance of phenological niches in understanding the maintenance of grassland stability under ongoing climate change.