ecological succession.pptx

Excellent description of ecological succession; Causes of succession; Classification of succession.

1. ECOLOGICAL SUCCESSION ADHEENA SHIJI 101

2. The concept, definition and reasons of succession. Classification of succession. Retrogressive changes. Concept of stable or climax community. Resilience of community. CONTENT

3. “Ecological succession is  the steady and gradual change in a species of a given area with respect to the changing environment” The term was coined by Hult

4. “ Change in community composition over time ” (Odum,1969) “ Succession refers to the directional predictable changes in community structure over time ” (Smith,1987)

5. Succession is orderly sequence of changes in the vegetation of previously bare area. It is directional hence predictable. The rate of change , the pattern of change and the limit of development are determined by the alteration brought about in physical environment by the existing community. It produce climax community , which is in dynamic equilibrium with the climate. The final or climax community determined by climate . (Phenomenon of convergence ) MAJOR CHARACTERS OF SUCCESSION

6. Primary and secondary succession (Based on starting) Autogenic and Allogenic succession ( Based on cause) Autotrophic and heterotrophic (Based on community) Hydrosere and xerosere ( Based on substratum) TYPES OF SUCCESSION

7. “ Primary succession is that take place on a primary bare area or area which has not previously inhabited by plants ”

8. “ Secondary succession is occur in a site which has become bare secondarily due to destruction of previous vegetation ”

9. Properties Primary Succession Secondary Succession Occurrence It takes place in areas which are lifeless or barren It takes place in areas which were previously inhabited or recently denuded Example Barren rock, ponds, desert , etc Natural calamities, covered under deforestation, etc Soil Soil is absent at the beginning of primary succession and the environment is not suitable for sustaining normal life forms. Soil is present at the beginning of secondary succession with some organisms Time Relatively slow and it takes approx. 1000 years or more. Relatively fast and it take approx 50-200 years. Observance Primary succession is much more difficult to observe than secondary succession.  Easy to observe

10. Humus Humus is absent in the starting as there is no soil Presence of Humus due to the previous occupants and their decomposition Pioneer Community(first biotic community) Pioneer community comes from outside often crustose lichen in a barren rock. Pioneer community develops partly from previous occupants and partly from migrants. Intermediary seral communities Intermediary seral communities are many as it takes long time for reaching climax stage. Intermediary seral communities are a few compared to primary succession.

11. “ Autogenic succession is the one resulting from change brought about by the organism within a community ” “ Allogenic succession is the habitat change occur by the action of outside factors like change in climate , soil leaching , increase in salt concentration in soil .”

12. Autogenic succession Allogenic succession It always occurs due to endogenous factors . It is caused by exogenous factors. Secondary succession begins with autogenic succession. Primary succession begins with allogenic succession and slowly proceeds towards autogenic succession. Example: accumulation of dead organic matter in the soil changes the nutrient composition of soil and microorganisms living in it. This is an example of autogenic succession. Example: floods, forest fires, volcanic eruptions, and global warming change the ecosystem over time.

13. “ Autotrophic succession involve the appearance and continued dominance of green or autotrophic plants .” “ Heterotrophic succession occur in an area rich in organic matters , there is dominance of microbes , actinomycete and other animals occur ”

14. Autotrophic succession Heterotrophic succession Autotrophic organisms have constant and early dominance Heterotrophic organism have constant and early dominance Begins with inorganic environment Begins with organic environment Presence of large population of plants Presence of more microbes , fungi etc. In the ecosystem increase in energy flow There is decrease in energy flow

15. 1 . XEROSERE : This succession takes place in dry areas like rock lithosere , psammosere ,and halosere . 2. HYDROSERE : This type of succession starts in the aquatic habitat and progresses from hydric to mesic conditions. 3. LITHOSERE : This type of ecological succession develops on exposed rock surfaces. 4. PSAMMOSERE : This type of ecological succession starts on the sand. 5. HALOSERE : The plant succession that starts on salty soil and saline water. 6 . SENILE : This type of succession begins on a dead matter of microorganisms.

16. PROCESS OF SUCCESSION

17. INVASION

18. CONCEPT OF CLIMAX “The climax community of an area during succession is the stabilized community which forms equilibrium with the environment”

19. Monoclimax theory The theory explains that similar type of community is present at climax stage in the given land area. In other words, succession begins in diverse areas like pond, rock and river will finally converge into a same single climax community decided by their regional climate THEORIES OF CIMAX

20. Polyclimax theory Climax is controlled by not a single factor but by several other factors. Various climax communities can be expected in the area which is under the control of different abiotic component such as moisture, soil, temperature and activities of different biotic factors . Existence of a number of climax communities, forming a mosaic correspond to the mosaic of habitat.

21. “Retrogressive succession or concept of degradation , it is the succession in which community become more simplistic and contain fewer species and less biomass over time . RETROGRESSIVE SUCCESSION

22. “Community resilience is broadly defined as  a community's collective capacity to function in, respond to, and potentially influence an environment characterized by continuous change, uncertainty, and crisis “. RESILIENCE OF COMMUNITIES

23. Odum , E P . The strategy of ecosystem development .Science 164, (262-270). Clement , F E. Nature and structure of climax . Journal of ecology 24, (252-284). Clerk G L. Elements of Ecology . Harvard university, 1959. (425-438). Sharma P D. Environmental Biology. University of Delhi, 2004 (136-144) http://epgp.inflibnet.ac.in REFERENCE