Abstract
Background and Aims Previous studies have focused on differences in leaf functional traits (LFTs) in response to N addition under spatiotemporal or species classification variations. However, in N-rich forest ecosystems, it is unknown whether continuous N input regulates plant phenology, further strengthening or weakening these differences. Methods We examined how N addition at 0, 20 (LN), and 40 kg N hm–2 a–1 (HN) affected the variations in LFTs (and trait-trait covariations) among seasons (April and August) and plant types in an N-rich evergreen broadleaf forest in western China. Results Along the vertical vegetation gradient (from trees to shrubs to herbs), the seasonal variation in LFTs diminished. Most plants had higher C and P contents in August than in April. The HN treatment reduced the seasonal variation in C content of trees and herbs, while it accentuated that of shrubs. Additionally, HN significantly decreased the differences in C and P between trees and both shrubs and herbs, while enhancing the differences in leaf N between shrubs and herbs in August. However, N addition did not significantly affect leaf pH, dry matter content, or specific leaf area. Only the N–P scaling in covariations decreased with increasing N addition. Conclusion High N input may aggravate this area to move towards N saturation and P limitation. The heterogeneous response among plants with different ecological adaptation strategies to N additions regulating the differences in LFTs on seasonal dynamics as well as plant types, and could have important implications for plant–soil feedback mechanisms concerning nutrient limitation.