Abstract: Fir forest is the zonal vegetation in West Sichuan alpine valley area. Based on the forest inventory data in Miyaluo, this paper analyzed the relationships between the tree height, DBH, volume, and distribution of fir forest and the ecological factors in the area, and discussed the most suitable habitats for the forest. It was shown that with increasing altitude, the tree height and DBH changed in single peak curve, while the volume had a fluctuated increase, which could be related to the characteristics of micro-environment and human disturbances. The suitable habitat of the fir forest was at an altitude ranged from 3500 to 4000 m a.s.l., with a soil depth from 50 to 79 cm, and a slope degree from 40° to 49°. In addition, the fir trees preferred the half-shady side of slope, or the superior shady side of mid- or top-slope. A large proportion of the fir forest concentrated within an altitude range from 3800 to 3900 m a.s.l.. Slope position was the most fundamental ecological factor affecting the fir forest community characteristics, followed by soil depth, slope, and aspect.

Key words: Mountain forest landscape, Landscape pattern, Landscape indices, Qilian Mountains, Xishui Natural Reserve