Effects of nitrogen addition on flowering phenology, functional traits and community structure of alpine meadow in the Eastern QinghaiTibet Plateau

In this study, the effect of nitrogen addition on the flowering time plant height of 30 common species in an alpine meadow of the QinghaiTibet plateau after 3 years was investigated. The effect of nitrogen addition on Community weighted means (CWMs) of two plant traits (CWMH) and (CWMSLA)was also studied. The community level phenology similarity and species composition similarity among nitrogen addition gradient were tested using a nonmetric multidimensional scaling (NMDS). The results showed that, Nitrogen addition significantly increased the height of species(P0.05). The effect of nitrogen addition differed between gramineous and forbs species. The first flowering day was delayed in gramineous species (P0.05). The first flowering day in forbs were either slightly advanced or delayed, but most of them have advanced the first flowering day (P0.05). As might be expected the leguminous species flowering time was insensitivity to nitrogen addition. Nitrogen addition significantly increased (CWMH) and (CWMSLA) (P0.05). Simpson's diversity Index decreased along with nitrogen addition level. Nonmetric multidimensional scaling (NMDS) ordination of phenologicallyweighed community similarity was among nitrogen addition gradient (Stress Value=0.08). The community level phenology similarity and species composition similarity were significantly decreased with nitrogen level, which implied that both community level phenology and community structure were responsive to nitrogen addition.