Abstract: To explore the effects of vegetation restoration after engineering application, we examined species composition, diversity, their relationships with environmental factors, and the niche of dominant species of restored vegetation after the Beichuan earthquake in Sichuan Province. The results showed that: (1) There were 74 plant species in the study area, belonging to 37 families and 72 genera. The dominant species in the woody layer and herb layer of the engineering area were Prunus salicina and Bidens pilosa, respectively, while the dominant species in the respective layers of the natural area were Platycladus orientalis and Iris confusa, respectively. (2) Results of CCA ordination showed that species could be divided into five groups in the engineering area and into three groups in the natural area. The importance of environmental factors(including engineering methods) affecting the species distribution in the engineering area was in order of: elevation > slope > aspect > pH > engineering method > soil moisture > slope position. Elevation, slope, and aspect were the main factors affecting species distribution in the engineering area. Species distribution in the natural area was affected by various factors. (3) Species richness and diversity of woody plants in the natural area were significantly higher than that in the engineering area, while the species richness and diversity of herbaceous plants in the engineering area were higher than that in the natural area. Altitude was the most important environmental factor affecting species richness and diversity of herbaceous layers in the engineering area, while slope position and engineering method were the main factors as for the woody layer in the engineering area. (4) Compared with the natural area, lower niche similarity ratio (0.0-0.4) and niche overlap value (0.0-0.5) of most species suggested weaker interspecific competition in the engineering area. Therefore, we proposed to plant more native dominant woody species in the engineering area.

Key words: Wheat, Nitrogen application, Nitrogen absorption and translocation, Grain yield, Grain protein content