Ecological succession - Wikipedia
Competency Relationships Between Organisms and the Environment. Ecological succession, pioneer species, and climax communities are discussed in. Succession as progressive change in an ecological community. Primary vs. secondary succession. The idea of a climax community. Ecological succession is the process of change in the species structure of an ecological .. Succession of micro-organisms including fungi and bacteria occurring within a microhabitat is known as microsuccession or serule. . and nutrients, their biotic relationships, availability of flora and fauna to colonize the area, chance.
As the climate warmed at the end of each ice age, great successional changes took place. The tundra vegetation and bare glacial till deposits underwent succession to mixed deciduous forest. The greenhouse effect resulting in increase in temperature is likely to bring profound Allogenic changes in the next century.
Geological and climatic catastrophes such as volcanic eruptions, earthquakes, avalanches, meteors, floods, fires, and high wind also bring allogenic changes. Mechanisms[ edit ] InFrederic Clements published a descriptive theory of succession and advanced it as a general ecological concept. Clements' concept is usually termed classical ecological theory. According to Clements, succession is a process involving several phases: Succession begins with the development of a bare site, called Nudation disturbance.
It refers to arrival of propagules. It involves establishment and initial growth of vegetation. As vegetation becomes well established, grow, and spread, various species begin to compete for space, light and nutrients. During this phase autogenic changes such as the buildup of humus affect the habitat, and one plant community replaces another.
A supposedly stable climax community forms. Seral community Pond succession or sere A: Emergent plants grow inwards, sediment accretes D: In many cases more than one seral stage evolves until climax conditions are attained. Depending on the substratum and climate, different seres are found. Changes in animal life[ edit ] Succession theory was developed primarily by botanists. In lichen stage the fauna is sparse.
It comprises few mites, ants and spiders living in the cracks and crevices. The fauna undergoes a qualitative increase during herb grass stage. The animals found during this stage include nematodes, insects larvae, ants, spiders, mites, etc. The animal population increases and diversifies with the development of forest climax community.
The fauna consists of invertebrates like slugs, snails, worms, millipedes, centipedes, ants, bugs; and vertebrates such as squirrels, foxes, mice, moles, snakes, various birds, salamanders and frogs. Microsuccession[ edit ] Succession of micro-organisms including fungi and bacteria occurring within a microhabitat is known as microsuccession or serule.
This type of succession occurs in recently disturbed communities or newly available habitat, for example in recently dead trees, animal droppings, exposed glacial till, etc.
Microbial communities may also change due to products secreted by the bacteria present. Changes of pH in a habitat could provide ideal conditions for a new species to inhabit the area. In some cases the new species may outcompete the present ones for nutrients leading to the primary species demise.
Changes can also occur by microbial succession with variations in water availability and temperature. Theories of macroecology have only recently been applied to microbiology and so much remains to be understood about this growing field. A recent study of microbial succession evaluated the balances between stochastic and deterministic processes in the bacterial colonization of a salt marsh chronosequence.
The results of this study show that, much like in macro succession, early colonization primary succession is mostly influenced by stochasticity while secondary succession of these bacterial communities was more strongly influenced by deterministic factors.
Barring major disturbances, it will persist indefinitely. This end point of succession is called climax. Climax community The final or stable community in a sere is the climax community or climatic vegetation.
It is self-perpetuating and in equilibrium with the physical habitat. There is no net annual accumulation of organic matter in a climax community. The annual production and use of energy is balanced in such a community.
The vegetation is tolerant of environmental conditions. It has a wide diversity of species, a well-drained spatial structure, and complex food chains. The climax ecosystem is balanced. There is equilibrium between gross primary production and total respiration, between energy used from sunlight and energy released by decomposition, between uptake of nutrients from the soil and the return of nutrient by litter fall to the soil.
Individuals in the climax stage are replaced by others of the same kind. Thus the species composition maintains equilibrium.
It is an index of the climate of the area. The life or growth forms indicate the climatic type. Types of climax[ edit ] Climatic Climax If there is only a single climax and the development of climax community is controlled by the climate of the region, it is termed as climatic climax. For example, development of Maple-beech climax community over moist soil. Climatic climax is theoretical and develops where physical conditions of the substrate are not so extreme as to modify the effects of the prevailing regional climate.
Edaphic Climax When there are more than one climax communities in the region, modified by local conditions of the substrate such as soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity, it is called edaphic climax.
Succession ends in an edaphic climax where topography, soil, water, fire, or other disturbances are such that a climatic climax cannot develop. Catastrophic Climax Climax vegetation vulnerable to a catastrophic event such as a wildfire. For example, in Californiachaparral vegetation is the final vegetation.
Competency Relationships Between Organisms and the Environment | BioEd Online
The wildfire removes the mature vegetation and decomposers. A rapid development of herbaceous vegetation follows until the shrub dominance is re-established.
This is known as catastrophic climax. Disclimax When a stable community, which is not the climatic or edaphic climax for the given site, is maintained by man or his domestic animals, it is designated as Disclimax disturbance climax or anthropogenic subclimax man-generated.
For example, overgrazing by stock may produce a desert community of bushes and cacti where the local climate actually would allow grassland to maintain itself. Subclimax The prolonged stage in succession just preceding the climatic climax is subclimax. Preclimax and Postclimax In certain areas different climax communities develop under similar climatic conditions.
If the community has life forms lower than those in the expected climatic climax, it is called preclimax; a community that has life forms higher than those in the expected climatic climax is postclimax. Preclimax strips develop in less moist and hotter areas, whereas Postclimax strands develop in more moist and cooler areas than that of surrounding climate. Theories[ edit ] There are three schools of interpretations explaining the climax concept: Monoclimax or Climatic Climax Theory was advanced by Clements and recognizes only one climax whose characteristics are determined solely by climate climatic climax.
The processes of succession and modification of environment overcome the effects of differences in topography, parent material of the soil, and other factors. The whole area would be covered with uniform plant community.
Communities other than the climax are related to it, and are recognized as subclimax, postclimax and disclimax. Polyclimax Theory was advanced by Tansley It proposes that the climax vegetation of a region consists of more than one vegetation climaxes controlled by soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity.
Climax Pattern Theory was proposed by Whittaker The climax pattern theory recognizes a variety of climaxes governed by responses of species populations to biotic and abiotic conditions.
According to this theory the total environment of the ecosystem determines the composition, species structure, and balance of a climax community. The environment includes the species responses to moisture, temperature, and nutrients, their biotic relationships, availability of flora and fauna to colonize the area, chance dispersal of seeds and animals, soils, climate, and disturbance such as fire and wind.Succession
The nature of climax vegetation will change as the environment changes. The climax community represents a pattern of populations that corresponds to and changes with the pattern of environment. The central and most widespread community is the climatic climax.
The theory of alternative stable states suggests there is not one end point but many which transition between each other over ecological time. Forest succession[ edit ] The forests, being an ecological system, are subject to the species succession process. They are capable of germinating and growing in direct sunlight. Once they have produced a closed canopythe lack of direct sun radiation at soil makes it difficult for their own seedlings to develop. It is then the opportunity for shade-tolerant species to become established under the protection of the pioneers.
When the pioneers die, the shade-tolerant species replace them. These species are capable of growing beneath the canopy, and therefore, in the absence of catastrophes, will stay. In addition, as these early species grow and die, they add to an ever-growing layer of decomposing organic material and contribute to soil formation. Photograph of succulent plants colonizing lava during primary succession on Maui. During primary succession on lava in Maui, Hawaii, succulent plants are pioneer species.
At each stage, new species move into an area, often due to changes to the environment made by the preceding species, and may replace their predecessors. At some point, the community may reach a relatively stable state and stop changing in composition. However, it's unclear if there is always—or even usually—a stable endpoint to succession, as we'll discuss later in the article. Secondary succession In secondary succession, a previously occupied area is re-colonized following a disturbance that kills much or all of its community.
A classic example of secondary succession occurs in oak and hickory forests cleared by wildfire. Wildfires will burn most vegetation and kill animals unable to flee the area.
Their nutrients, however, are returned to the ground in the form of ash. Since a disturbed area already has nutrient-rich soil, it can be recolonized much more quickly than the bare rock of primary succession. Before a fire, the vegetation of an oak and hickory forest would have been dominated by tall trees. Their height would have helped them acquire solar energy, while also shading the ground and other low-lying species.
After the fire, however, these trees do not spring right back up. Instead, the first plants to grow back are usually annual plants—plants that live a single year—followed within a few years by quickly growing and spreading grasses. The early colonizers can be classified as pioneer species, as they are in primary succession. Eventually, barring further disturbances, the oak and hickory trees will become dominant and form a dense canopy, returning the community to its original state—its pre-fire composition.
This process of succession takes about years. The path and endpoint of succession The early ecologists who first studied succession thought of it as a predictable process in which a community always went through the same series of stages. They also thought that the end result of succession was a stable, unchanging final state called a climax community, largely determined by an area's climate.
For instance, in the example above, the mature oak and hickory forest would be the climax community. Today, the idea of a set path for succession and a stable climax community have been called into question. Rather than taking a predetermined path, it appears that succession can follow different routes depending on the specifics of the situation.
Ecosystems may experience frequent disturbances that prevent a community from reaching an equilibrium state—or knock it quickly out of this state if it manages to get there.
Attribution This article is a modified derivative of the following articles: Download the original article for free at http: Tyler Miller and Scott E. Cengage Learning, Last modified March 27,