Stoichiometric traits (N:P) of understory plants contribute to reductions in plant diversity following long-term nitrogen addition in subtropical forest

Nitrogen enrichment is pervasive in forest ecosystems, but its influence on understory plant communities and their stoichiometric characteristics is poorly understood. We hypothesize that when forest is enriched with nitrogen (N), the stoichiometric characteristics of plant species explains changes in understory plant diversity. A 13 year field experiment was conducted to explore the effects of N addition on foliar carbon (C): N: phosphorus (P) stoichiometry and understory plant species richness in a subtropical Chinese fir forest. Four levels of N addition were applied: 0, 6, 12, and 24 g m-2 yr-1. Individual plant species were categorized into resistant plants, intermediate resistant plants, and sensitive plants based on their response to nitrogen addition. Results showed that N addition significantly decreased the number of species, genera and families of herbaceous plants. Foliar N:P ratios were greater in sensitive plants than resistant or intermediate resistance plants, while intr...