Plant Succession, Causes and it's Types

This presentation describes the plant succession, causes and its main types that is primary and secondary succession with examples in detail. It is related to the Ecology topic in Botany.

1. SUCCESSION

2. Succession The term was given by Hult (1885). It is a sequence of changes in the community structure of an ecosystem over a period of time. A change in the composition and nature of plant community of a habitat over the years is known plant succession.

3. Example For example, if a cultivated field is left fallow for some time. Annual weeds will appear in the first year. Numerous perennial species will appear in the second year. In later years, few bushes and some trees will make their appetence. In this way there is a change in the plant communities year after year. So, succession is a process in which there is a successive occupation of an area by different plant communities.

4. Pioneer species Grasses Forest Shrubs Bare Rocks Trees Climax community is the stable endpoint of succession which lasts a long time

5. Causes of Succession There are two main causes of succession. Physiographic Factors (Physical Causes). Those factors which are associated with the physical nature of the area. Biotic factors. A change in the environment is produced by the community.

6. Any of the factors, apart from climatic, biotic and edaphic factors. That affect the prevailing conditions within a habitat and the distribution of the plants and animals. It includes the physical and chemical factors of the environment. Such factors include the topography of the area, altitude, drainage conditions, degree of erosion, slope of the land, etc. Physiographic Factors

7. A change in the habitat may be produced by: The silting in of a lake or pond, Chemical changes by leaching or accumulation of salts. Flooding of plains. Soil erosion. Change in temperature. Rainfall. Melting of glaciers. Land Sliding. Volcanic action. Such changes will cause change in community. Plant successional changes are rapid in habitat with moderate environment, but such changes become slow in area with extremes of environment. Physiographic Factors

8. Silting of Lake or Pond

9. Flooding of Plains

10. Melting of Glaciers

11. Land sliding

12. Volcanic Action

13. Soil Erosion

14. Rainfall

15. A change in the environment is produced by the community. Such as various activities of organisms. Many biological or living agencies also affects the vegetation in many aspects. Grazing, cutting, clearing, cultivation, harvesting and deforestation, all caused by living agencies, are directly responsible for vegetational change. The parasitic plants and animals also affect the vegetation and destroy it. Biotic Factors

16. Biotic Factors The death and decay of organisms add organic matter. It releases humus by decomposition. It increases water holding capacity. It also increases the nutrients content of soil which affects soil organisms. By these factors, habitat is modified and become less favorable for the established species. And become more favorable for new coming species.

17. Types of Succession There are two types of succession. Types of succession Primary Succession Development of plant community on barren area. Secondary Succession Development of plant community on distributed area.

18. Primary Succession The development of plant community in a barren area where no community existed before is called primary succession. It usually starts with the lower organisms. It take a longer time to reach the climax community. An example of an area in which a community has never lived before would be a new lava or rock from a volcano that makes a new island.

19. The stages of primary succession include pioneer species including microorganisms, plants (lichens and mosses), grassy stage, smaller shrubs and trees. The first group of organisms establishing on a bare rock or sand is known as pioneers , primary community. Animal begin to return when there is food there for them to eat. When it is a fully functioning ecosystem, it has reached to the climax community stage. That type of vegetation which develop ultimately will permanent and will be in equilibrium with the climate is known as climax communities. It is the highest type of vegetation e.g., trees in a forest. A stage after which no plant succession take place is called climax stage. Primary Succession

20. Types of Primary Succession Following are it’s type depending upon the substratum and based on it’s habitat. ( hydric , mesic & xeric) Hydarch: Succession beginning in watery habitats like ponds, lakes and marshes is called hydarch while sequence of its developmental stages is called hydrosere. Wet habitat is hydric . Xerarch: Succession beginning on dry habitat is termed as xerarch . Its developmental stages are called xerosere while the dry habitat is termed as xeric.

21. Hydrach has two habitats. Hydrosere: It is stage where plants colonize in fresh water, as at a pond margin. e.g. Monmouth shire-ox-bow lakes. Halosere: It is stage where plant colonize at the surface of saline soil, salt marshes and sea estuaries. e.g. The North shore of the Gower, lanrhidian salt marsh. Xerarch has two habitats. Lithosere : Successional stages at the surface of a rock is called lithosere . Psammosere : Successional stages at the surface of sandy soil. Types of Primary Succession (Contd.)

22. Hydarch

23. Xerarch

24. Secondary Succession Secondary succession , type of succession in which plants and animals re-colonize a habitat after a major disturbance. Devastating flood Wildfire Landslide Lava flow Human activity (e.g., farming or road or building construction) Secondary succession starts from previously built up substrata with already existing living matter. It starts on already colonized surface. It may start from fairly complex organisms. It takes a shorter time or duration to reach a climax community.

25. Secondary Succession

26. If damage is slight, the secondary succession become primary. If damage is severe, the secondary succession may remain different. The damage to the original communities modifies the habitat by changing the moisture conditions, organic matter may be destroyed. Nutrients in the soil become lesser. Soil erosion may rapid. It happens more rapidly than primary succession. Because previous community has left its marks in the form of improved soil and seeds. The stages of secondary succession are similar to those of primary succession. Primary succession always begins on a barren surface, whereas secondary succession begins in environments that already possess soil. Secondary Succession

27. Secondary Succession An example of Secondary Succession by stages: An area of growth. A disturbance, such as a fire, starts. The fire destroys the vegetation. The fire leaves behind empty, but not destroyed soil. Grasses and other herbaceous plants grow back first. Small bushes and trees begin to colonize the public area. Fast-growing evergreen trees and bamboo trees develop to their fullest, while shade-tolerant trees develop in the understory. The short-lived and shade-intolerant evergreen trees die as the larger deciduous trees overtop them. The ecosystem is now back to a similar state to where it began. Imperata grassland

28. Imperata  Grasslands