Question

Correct sequence of stages of succession of a lithosere is?

• A. Foliose lichens $\to$ Crustose lichens $\to$ Mosses $\to$ Annual grasses $\to$ Perennial grasses $\to$ Shrubs $\to$ Trees
• B. Crustose lichens $\to$ Foliose lichens $\to$ Mosses $\to$ Perennial grasses $\to$ Annual grasses $\to$ Shrubs $\to$ Trees
• C. Crustose lichens $\to$ Foliose lichens $\to$ Mosses $\to$ Annual grasses $\to$ Perennial grasses $\to$ Shrubs $\to$ Trees
• D. Crustose lichens $\to$ Foliose lichens $\to$ Mosses $\to$ Annual grasses $\to$ Shrubs $\to$ Perennial grasses $\to$ Trees

Answer 1

The correct option is C Crustose lichens $\to$ Foliose lichens $\to$ Mosses $\to$ Annual grasses $\to$ Perennial grasses $\to$ Shrubs $\to$ Trees

A lithosere (a sere originating on rock) is a plant succession that begins life on a newly exposed rock surface, such as one left bare as a result of glacial retreat, tectonic uplift as in the formation of a raised beach, or volcanic eruptions. The following points highlight the the seven main stages of lithosere in plants. The stages are:- 1. Crustose Lichen Stage 2. Foliose and Fruticose Lichen Stage 3. Moss Stage 4. Herb Stage 5. Shrub Stage 6. Trees Stage.

Crustose Lichen Stage: Lichen species like Graphis Rhizocarpon, Rinodina and Lecanora forms are the pioneer community in a lithosere, as they can tolerate desert or extreme hot condition. Organic acids produced by lichens leach the rock surface and release minerals for proper growth of lichens. Crustose lichens can adhere to the surface of rock and absorb moisture from atmosphere; therefore, these colonize the barren surfaces of rocks first. When these lichens die their thalli are decomposed and add humus. This promotes soil formation and the environment becomes suitable for growth of foliose and fruticose type of lichens.

Foliose Lichen Stage: Foliose lichen retain more water and accumulate more soil particles, helping in the development of a fine layer of soil on the rock surface. As the soil formation proceeds it leads to the growth of foliose lichens. They can absorb and retain more water and are able to accumulate more dust particles. Their dead remains are decomposed to humus which mixes with soil particles and help building substratum and improving soil moisture contents further.

Moss Stage: Accumulation of soil and humus leads to the growth of mosses. The spores of xerophytes mosses, are brought to the rock where they succeed lichens. Their rhizoids penetrate soil on the rocks. The bodies of mosses are rich in organic and inorganic compounds. When these die they add these compounds to the soil, increasing the fertility of the soil. As mosses develop in patches they catch soil particles from the air and help increase the amount of substratum.

Herb Stage: Death and decay of mosses produce a mat of organic moss rich in organic soil, that help the germination to seeds of hardy grasses. Their roots penetrate deep down, secrete acids and enhance the process of weathering. Leaf litter and death of herbs add humus to the soil. As a result the xeric conditions begin to change and biennial and perennial herbs and xeric grasses. These climatic conditions favor growth of bacterial and fungal populations, resulting in increase in decomposition activity.

Shrub Stage: The herb and grass vegetation is replaced by shrub species. This results in dense organic soil and making conditions unfavorable for the growth of herbs, which then begin to migrate. The soil formation continues and its moisture content increases. Further weathering or rocks and death of herbs make the habitat more suitable for the growth of shrubs. Since the shrubs are larger in size and their roots penetrate more deeply in the rocky substratum causes more weathering and soil formation.

Tree stage: Change in environment favors colonization of tree species. The trees begin to grow among the shrubs and establish themselves. The kind of tree species inhabiting the area depends upon the nature of the soil. In poorly drained soils oaks establish themselves. The trees form canopy and shade the area.

So the correct option is 'crustose lichens $\to$ foliose lichens $\to$ mosses $\to$ annual grasses $\to$ perennial grasses $\to$ shrubs $\to$ trees'