Question

The correct order of succession in xerarch is
(a) Annual herb stage, perennial herb stage, lichen moss stage, scrub stage, forest
(b) Perennial herb stage, annual herb stage, lichen moss stage, scrub stage, forest
(c) Lichen moss stage, annual herb stage, perennial herb stage, scrub stage, forest
(d) Forest, scrub stage, annual herb stage, perennial herb stage, lichen moss stage

Answer 1

Hint: This type of succession is limited by water availability as it occurs in dry conditions like sand deserts, rock deserts, etc. It begins with the formation of bare rocks by glaciers or volcano eruptions and reaches up to forest as a climax stage.

Complete answer:
When a steady and gradual but predictable change occurs in a species of a given area concerning the changing environment, it is called ecological succession. Xerarch succession is also called Xerosere as it occurs in xeric conditions like extremely dry environments and in this succession the development of species at different stages is limited by water availability. Xerosere begins when the bare rocks are produced and are colonized by lichens and mosses. These are followed by herbs and shrubs and finally, trees develop which in turn, form forest as the climax community in that environment.

Additional information:
1. The lichens that first colonize bare rocks are mainly foliose and fruticose lichens with leaf-like thalli in the former while the latter is like small bushes. They can absorb and retain water and thus promote further developmental stages in the succession.
2. The trees that are generally found in such environmental conditions are oak-like trees that form canopy and shade the area. The shaded area also promotes the growth of shade-loving vegetation as mosses and ferns grow well in these areas as secondary vegetation.

So, the correct answer is ‘Lichen moss stage, annual herb stage, perennial herb stage, scrub stage, forest’.

Note: Ecological succession is of four types – Primary succession, Secondary succession, Cyclic succession, and Seral community.
The seral community is further divided into seven different types – Hydrosere, Xerosere, Lithosere, Psammosere, Halosere, Senile, and Eosere.