Vegetation-Erosion Dynamics - River Dynamics and Integrated River Management - page 68

Vegetation cover increases with increasing rainfall and soil depth. In the area with insufficient soil, the
thickness of the soil layer determines the average height of vegetation. Essentially, the weight of the
roots of a plant and the soil grasped by the roots must be greater than the weight of the over ground part
of the plant. Figure 2.19 shows the vegetation on the north part of Taihang Mountain in the northern China.
This area is covered mainly with dolomite limestone. The rock is weathered mainly by dissolution by
rainfall containing CO 2 . In the process no granular material is produced. Therefore, there is a thin layer
of soil on the mountain and poor vegetation may develop in this area.
Fig. 2.19 There is a very thin layer of soil on the north part Taihang Mountain in the northern China. Only a few
species of shrubs can grow in this area, and, thus, the vegetation is poor
In many places, human activities have completely or partly changed the vegetation. According to the
extent of impact of human activities the vegetation may be classified into primitive vegetation, reforested
vegetation, and domestic vegetation. Primitive vegetation, such as virgin forest, has not been disturbed
by human activities. The floral community usually consists of complex species composition. Most of the
primitive vegetation in the world has been destroyed by forest fire, logging, and other natural disasters
and human activities. There are only several plots of primitive vegetation in high mountainous areas.
Figure 2.20 shows a primitive forest in the Jiuzhai basin in western Sichuan, China.
Fig. 2.20 Primitive vegetation in the Jiuzhai basin in western Sichuan, China