Explain how xerarch succession progresses from xeric to mesic condition and forms a stable climax community.

Lichens that grow on the rocks secrete acids which help in weathering of rocks and thus forming soil. The gaps in the soil formed due to the acid activity create ways for the growth of small plants such as bryophytes, which have the capability to grow in a very small amount of soil. These small plants are succeeded by higher plants and after several stages lead to form a stable climax community.