Xerarch succession : Xerarch succession takes place in dry areas, and the series progress from xeric to mesic condition.
In primary succession on rocks the pioneer species i.e., lichens secrete acids to dissolve rock, helping in weathering and soil formation. These later pave way to some very small plants like bryophytes which are able to take hold in the small amount of soil. They are with time, succeeded by bigger plants and after several more stages ultimately a stable climax forest community is formed.
The climax community remains stable as long as the environment remains unchanged. With time the xerophytic habitat gets converted into a mesophytic one.
The stages in xerarch succession are as follows :
In secondary succession, the species that invade depends on the condition of the soil, availability of water and the environment as also the seeds or other propagules present. Since soil is already there, the rate of succession is much faster and, hence, climax is also reached more quickly. Primary succession is a very slow process, taking about thousands of years for the climax to be reached.
Another important fact is to understand that all succession, whether taking place in water or on land, proceed to a similar climax community, the mesic.
