Shrub Stage - Xerarch
Sufficient soil is formed in the herbs stage, for supporting the woody plants or the shrubs. They migrate with the help of seeds or rhizomes from the adjacent areas. Examples are: species of Rhus and Physocarpus. The shrubs soon develop into dense vegetation. The habitat is considerably modified. The herbs are shaded by the overgrowing shrubs. They no longer find it possible to thrive in such a situation and are, therefore, completely replaced by the shrubs.
The shrubby vegetation adds a lot of organic matter to the soil, through leaves and other plant parts. The soil is thus enriched with considerable amount of humus. The huge mass of roots of the shrubs corrodes the rocks. The enriched soil attains greater capacity for holding water. The soil is shaded, and, therefore, evaporation of water is considerably reduced. The humidity is increased over such areas. All these favour the growth of seedlings of trees which start invading the area.