Xerosere
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Ecological succession begins on bare rock surfaces through pioneering crustose lichens. As lichens decompose, they provide nutrients for mosses to grow. Moss growth traps more soil particles and creates suitable conditions for herbs. Herbaceous plants further weather the rock and add humus. Shrubs later invade and are followed by trees, which constitute the climax forest community. Multiple intermediate seral stages typically evolve over time as the ecosystem advances towards its climax conditions.
Xerosere
- 1. Ecological succession on elk a bare rock xerosere
- 2. Screen clipping taken: 20-02-2013, 22:54 Sere and seral community • an intermediate stage found in an ecosystem advancing towards its climax community • in many cases more than one seral stage evolves until climax conditions are attained
- 3. Screen clipping taken: 20-02-2013, 23:45 Bare rocks The first form of life originates at such places which do not had life such as an island formed after a volcanic activity or a retreating glacier
- 4. crustose lichen stage A lichen is an important pioneer in primary succession composed of a photosynthesizing algae, and a fungi absorbing nutrients from rock and holds water. Together they break down rock Soil accumulates as dust particles trapped in cracks in rock Lichens decompose providing food for mosses
- 5. Foliose lichen stage They can absorb more water and are able to accumulate more dust particles. The shallow depressions in the rocks become filled with sold and topsoil layer increases further. These autogenic changes favor growth and establishment of mosses.
- 6. Moss stage As mosses develop in patches they catch soil particles from the air and help increase the amount of substratum. The changing environment leads to migration of lichens and helps invasion of herbaceous vegetation that can out-compete mosses.
- 7. Herb stage Herbaceous weeds, mostly annuals such as asters, evening primroses, and milk weeds, invade the rock. Their roots penetrate deep down, secrete acids and enhance the process of weathering. Leaf litter and death of herbs add humus to the soil
- 8. Shrub stage The herb and grass mixture is invaded by shrub species, such as Rhus and Phytocarpus. Early invasion of shrub is slow, but once a few bushes have become established, birds invade the area and help disperse scrub seeds.
- 9. Climax stage The succession culminates in a climax community, the forest. Many intermediate tree stages develop prior to establishment of a climax community
- 10. thank you Made by:- Khursheed alam khan
Editor's Notes
- #3: F.E. Clement (1916) developed a descriptive theory of succession and advanced it as a general ecological concept. His theory of succession had a powerful influence on ecological thought. Clement's concept is usually termed classical ecological theory. According to Clement, succession is a process involving several phases:
- #4: Bare rocks are produced when glaciers recede or volcanoes erupt. Erosion of these rocks is brought by rain water and wind loaded with soil particles. The rain water combines with atmospheric carbon dioxide that corrodes the surface of the rocks and produce crevices. Water enters these crevices, freezes and expands to separate boulders. These boulders move down under the influence of gravity and wear particles from the rocks. Also when the wind loaded with soil particles strikes against the rocks, it removes soil particles. All these processes lead to formation of a little soil at the surface of these bare rocks. Animals such as spiders which can hide between boulders or stones invade these rocks. These animals live by feeding on insects which have been blown in or flown in. Algal and fungal spores reach these rocks by air from the surrounding areas. These spores grow and form symbiotic association, the lichen, which act as pioneer species of bare rocks. The process of succession starts when autotrophic organisms start living in the rocks.