How many types of succession are there

Succession in a dry habitat. Succession on a bare rock surface. Succession initiating on sandy regions. Succession starting in saline soil or water. Succession of microorganisms on dead matter. Development of vegetation in an era. Examples of Ecological Succession. Following are the important examples of ecological succession:.

Acadia National Park. This national park faced a dreading wildfire. Restoration of the forest was left on to Mother Nature. In the initial years, only small plants grew on the charred soil. After several years, the forest showed diversity in tree species. However, the trees before the fire were mostly evergreen, while the trees that grew after the fire turned out to be deciduous in nature.

Ecological Succession of Coral Reefs. Small coral growths colonize the rocks. These polyps grow and divide to form coral colonies. The shape of the coral reefs attracts small fish and crustaceans that are food for the larger fish. Thus, a fully functional coral reef is formed.

Causes of Ecological Succession. Some important causes may be defined as below:. Climatic Causes: these can be rainfall, temperature variations, humidity, gas composition, etc.

Biotic Causes: the organisms in a community compete to thrive for existence. Some of them are lost in the process while some new ones are incorporated. External Causes: soil conditions are affected by the process of migration, invasion, and competition amongst various species.

Characteristics of Ecological Succession. Ecological succession has subsequent characteristics:. It results from the disparity in the physical atmosphere of the community. It is a systematic procedure of community development. It involves variations in species structure and it increases the diversity of species. Nutrient variation regulates the settlement of new communities. Succession operates in a stabilized ecosystem.

Mechanism of Ecological Succession. The entire process of primary succession is accomplished through a series of progressive steps followed one after another. The different sequential steps may be outlined as below:. It is a process of formation of a bare area without any form of life for the arrival of new species. The causes of nudation may be:. For example, if an oak-hickory forest had a severe forest fire which destroyed most of the trees, that forest system would eventually return to the climax community, defined by oak- and hickory-dominated species.

This idea, that an ecosystem could self-form, or self-renew into a stable climax community, became very popular in the s. Figure 2: Two contrasting views of succession A The super-organism concept, where groups of species are tightly associated, and are supplanted by other groups of tightly associated species. B The individualistic concept, where individual species independently respond to environmental conditions.

Each curve on the graphs represents the abundance of a single species. While the concept of a climax community is still viable today, the super-organism concept was opposed by another ecologist, Henry Gleason.

Gleason argued that communities were individualistic; that is, communities were only the fortuitous assembly of species, and that there was no such thing as a climax state for ecosystems.

Figure 3: Changes over time in total plant species richness over time at select sites on Mount Saint Helens, WA Plant reestablishment 15 years after the debris avalanche at Mount St. Helens, Washington. For example, species diversity tends to increase with the successional age of an ecosystem. After the eruption of Mount St. Helens in the United States in , ecologists monitoring the return of plant life to the mountain observed a steady increase in species diversity over time Figure 3.

Eugene Odum, an ecosystem ecologist, described several predictable differences between early and late successional systems. For example, early successional systems tend to have smaller plant biomass, shorter plant longevity, faster rates of soil nutrient consumption, a reduced role for decomposer organisms, more open and rapid biogeochemical cycling, higher rates of net primary productivity, lower stability, and lower diversity than late successional systems Odum Similarly, Fakhri Bazzaz characterized early and late successional systems based on the physiology of plants associated with these stages.

Early successional plants tend to have high rates of photosynthesis and respiration, high rates of resource uptake, and high light compensation points, whereas late successional plants often have opposite characteristics Bazzaz Facilitation is the most common mechanism proposed to explain succession.

However, other possible mechanisms included tolerance, inhibition, and random colonization. Since , the glacier filling Glacier Bay has steadily been retreating Figure 4a.

Researchers have characterized primary succession in this system, where plant communities progress from pioneer species i. Both facilitation and inhibition act as mechanisms regulating succession in this system Figure 4b. For example, both Dryas and alders increase soil nitrogen, which increases the establishment and growth of spruce seedlings.

However, both Dryas and alders produce leaf litter which can inhibit spruce germination and survival. B Summary of facilitative and inhibitory effects of each successional stage of vegetation on spruce seedling growth.

Figure modified from Chapin et al. A classic study of secondary succession was conducted by Catherine Keever In this study, Keever characterized succession in an old field after agricultural use had ceased. She observed a predictable shift in plant community composition following field abandonment, with horseweed Erigeron canadense dominating fields one year after abandonment, white aster Aster pilosis dominating in year two, and broomsedge Andropogon virginicus dominating in year three Figure 5.

She found that life history strategies of individual species, seed dispersal, allelopathy biochemical production by a plant which alters growth and survival of other plants or itself , and competitive interactions among species, led to this predictable pattern of succession.

Figure 5: Keever's observed pattern of succession in North Carolina agricultural old fields Figured modified from Keever Bazzaz, F. Physiological ecology of plant succession. Annual Review of Ecology and Systematics 10 , Chapin, F.

Mechanisms of primary succession following deglaciation at Glacier Bay, Alaska. Ecological Monographs 64 , Clements, F.

Nature and structure of the climax. Journal of Ecology 24 , Connell, J. Mechanisms of succession in natural communities and their role in community stability and organization. American Naturalist , Cooper, W. The recent ecological history of Glacier Bay, Alaska: the present vegetation cycle. Ecology 4, Cowles, H. The ecological relations of the vegetation on the sand dunes of Lake Michigan. Botanical Gazette 27 , , , , Gleason, H. The individualistic concept of the plant association.

Bulletin of the Torrey Botanical Club 53 , Grime , J. Plant strategies and vegetation processes. Horn, H. The ecology of secondary succession.

Annual Review of Ecology and Systematics 5 , Hubbell, S. Huston, M. Plant succession- life history and competition. Keever, C. Causes of succession on old fields of the Piedmont, North Carolina. These stages, characterised by the presence of different communities, are known as 'seres'. Communities change gradually from one sere to another. The seres are not totally distinct from each other and one will tend to merge gradually into another, finally ending up with a 'climax' community. Succession will not go any further than the climax community.

This is the final stage. This does not however, imply that there will be no further change. When large organisms in the climax community, such as trees, die and fall down, then new openings are created in which secondary succession will occur.

Many thousands of different species might be involved in the community changes taking place over the course of a succession. For example, in the succession from freshwater to climax woodland. The actual species involved in a succession in a particular area are controlled by such factors as the geology and history of the area, the climate, microclimate, weather, soil type and other environmental factors.

For example, the species involved in a succession from open freshwater to climax woodland in Central Africa, would be quite different to those which have been quoted in these pages as occurring in Britain.

However, the processes involved would be the same. Succession occurs on many different timescales, ranging from a few days to hundreds of years. It may take hundreds of years for a climax woodland to develop, while the succession of invertebrates and fungi within a single cow pat cow dung , may be over within as little as 3 months.