Abstract: To reveal the phenotypic variation of Bromus inermis, we analyzed 13 phenotypic traits of 450 Bromus inermis individuals collected from five regions on the northern slope of Tianshan Mountains. The results showed variation in phenotypic traits of Bromus inermison the northern slope of the Tianshan Mountains, but with small coefficient of variation (0.294).  The variation of phenotypic traits among regions was greater than that within regions. The variation of phenotypic traits in the middle section of the northern slope of the Tianshan Mountains was significantly different from that in the eastern and western sections. The variation in the middle section increased with altitude, whereas that in the eastern and western parts showed an opposite pattern.  The 13 traits had a wide range of variation among regions, with the variation of tiller number being the largest. The trait indicators were positively correlated with the longitude and latitude. The mean annual temperature and mean annual precipitation were significantly correlated with a few traits such as ear length and root length.  The differences in phenotypic traits among regions were mainly presented in the reproductive branch height, spike length, leaf length and leaf width.  There was a large plant stature in the middle section of the northern slope of the Tianshan Mountains, and the large plant stature mainly came from the low altitude. In summary, climate in the middle section of the northern slope of the Tianshan Mountains was more suitable for the growth of Bromus inermis. The growth of Bromus inermis at low-altitude was better than those of the other two altitudes.

Key words: land use change, climate change, SWAT model, runoff change, scenario simulation, Liuxihe Watershed.