In Gongga moutainous region roughly S—N trending trmenous differences in altitude and crest line have led to the distinct heat and water differences between the eastern and western slopes in the vertical direction. These differences are the dominant factors that formed vertical natural zones.
The vertical natural zonation is the natural synthesis composed of geomorpology, climate, vegetaiton, soil and other elements. Various vetical natural zones result from interaction of above factors. According to the synthetic view of physical gegraphy, the east slope and south slope in this region are divided into seven vertical zones, the west slope is divided into five vertical zones and the north slope divided into six zones.
1. Mountain subtropical evergreen broad-leaved forest zone at alt. 1000-2400m.
1) Valley subtropical shrub, meadow, and Yunnan pine forest subzone at alt. 1000-1600m.
2) Mountain subtropical evergreen broad-leaved forest subzone at alt. 1600-2000m.
3) Mountain subtropical evergreen broad-leaved mixed forest subzone at alt. 2000-2400m.
2. Mountain warm-temperate coniferous and broad-leaved mixed forest zone at alt. 2400-2800m.
3. Mountain cold-temperate dark coniferous forest zone at alt. 2800-3800m.
1) Mountain cold-temperate spruce, fir and Chinese hemlock forest subzone at alt. 2800-3100m.
2) Mountain cold-temperate fir forest subzone at alt. 3100-3500m.
4. Subalpine subfrigid shrub and meadow zone at alt. 3500-4200m.
5. Alpine frigid meadow zone at alt. 4200-4600m.
6. Appine frigid, cold desert zone with aparse grass at alt. 4600-4900m.
7. Polar alpine nival zone at alt.＞4900m.
The base of the vertical natural zonal spectra on the west slope belongs to the meantain cold-temperate dark coniferous zone. All zons above it are differnt between the west and east slopes not only in vegetation comonents, community texture features and soil slopes, but also in altitude.
Because this region is located in the transitional zone between Sichuan Basin and Qinghai-Xizang Plateau, the vertical natural zones on both east and west slopes are similar to those of the west peripheral mountains of Sichuan Basin and the piedmont-plain in the western Sichuan of the eastern Qinghai-Xizang Plateau in many ways repectively. The versical natural zones on the east slope have the basic characterisrties of evergreen broad-leaved forest zone in the east subregion of Chines subtroical humid region; but on the west slope they have the charateristics of subhumid meadow and coniferous forest zones on the Qinghai-Xizang Plateau. Therefore, the crest line of Gongga mountain may be regarded as an important demarcation line of "0" unit (i. e. zone ir region) of natural regionalization of the western China, as well as the first-claa line of natural regionalization in this region. On the base of the prineiple that textures in the same subzone should be slope similar, the east subzone of subtropical humid region. Starting from the above region-alization, the natural regions and small regions were classified. In the different small regions, main natural characteristics and directions of land use are different.