Ecological Succession
1.0Ecological Succession Definition
“The orderly changes in community structure and function in an ecosystem with time mediated through the modifications in the physical environment ultimately leading to a stable community over that area.”
2.0What Is Ecological Succession?
The process of Ecological Succession is a systematic progression of changes in the species structure and function within a community over time. This process is both continuous and directional, making it predictable.
This natural phenomenon arises from modifications in the physical environment by the community's species. These changes result from ongoing competition among species for essential physical factors such as light and space, as well as resources like energy and nutrients. Despite the community's influence, the modifications in the physical environment play a crucial role in determining the patterns, rates of change, and overall development during the succession process.
The ultimate outcome of ecological succession is the establishment of a stable ecosystem featuring a dominant species, known as the climax species. This climax species achieves a state of equilibrium with the surrounding environment.
The entire sequence of communities that successively replace one another in a specific area is termed a "sere," and the intermediary communities are referred to as "seral stages." These stages include the grass stage, herb stage, shrub stage, etc. The initial phase is labeled the pioneer stage, characterized by an early successive pioneer plant community. The last or terminal stage is recognized as the climax. The pioneer community is more easily replaced by the next seral stage, while the climax community is considered a more mature and stabilized stage within the ecosystem.
3.0Characteristics of Ecological Succession
- Transition from Short-Lived to Long-Lived Plants: The process of ecological succession involves a gradual shift in plant life from short-lived to long-lived species.
- Continual Changes Toward Stability or Climax: Communities undergo ongoing and continuous changes, progressively moving towards a state of stability or climax during ecological succession.
- Enhanced Species Diversity, Biomass, Niche Specialization, and Humus Content: Ecological succession fosters an increase in species diversity, biomass, niche specialization, and the accumulation of humus content in the soil.
- Reduction in Net Community Productivity or Annual Yield: As succession unfolds, there tends to be a decrease in the net community productivity or the annual yield of the ecosystem.
- Predictable Future Seral Communities: The directionality of ecological succession allows for the prediction of future seral communities, making it a process with a foreseeable trajectory.
- Parallel Processes of Succession and Evolution: The progression of ecological succession and evolution can be viewed as parallel processes, each influencing and shaping the dynamics of ecosystems over time.
- Focus on Vegetational Changes Impacting Fauna and Decomposers: Although the description of ecological succession often centers on vegetational changes, it is crucial to recognize that these alterations in plant life also have profound effects on the availability of food and shelter for various animals. Consequently, as succession advances, both the numbers and types of animals and decomposers within the ecosystem undergo significant transformations.
4.0Causes of Succession
- Biotic factors – The action of each seral community with its environment makes the area less favorable for itself and more favorable for the next seral community in the succession.
- Physiographic factors – These include climatic and other physical factors like soil erosion, soil deposition, landslide, volcanic lava. These all factors make an area barren.
5.0Types of Ecological Succession
On the basis of nutrient availability, succession are of two types : primary and secondary succession.
Primary Succession
Primary succession initiates in newly formed areas characterized by elementary environmental conditions, such as a bare expanse resulting from phenomena like lava flow, landslides forming new ponds, sand dune formation, or the exposure of rock surfaces due to retreating glaciers. In these pristine areas, there is an absence of any biological legacy, including vegetation, seed banks, or organic matter. Initially unoccupied by any community, the introduction of the first organisms depends on immigration, as there are no existing seeds or propagules.
Example of primary succession :
Barren land devoid of soil and succession begins with pioneer species like lichens and mosses colonizing the volcanic rock. These resilient organisms thrive in harsh conditions, breaking down the rock and contributing to soil development. Over time, as soil accumulates, more advanced plants such as ferns and grasses take root. The ecosystem evolves further, with shrubs and trees eventually establishing themselves, resulting in a diverse and mature community.
Secondary Succession
Secondary succession commences in an area that was previously inhabited by a community but has been stripped of vegetation due to various natural or human-induced activities such as fire, storms, tree cutting, disease outbreaks, cultivation, or other biotic interventions. Over the course of several years, a new community begins to reclaim and occupy the area, marking the onset of secondary succession. Although the region may lack visible living matter above ground, its substratum is enriched with nutrients, organic matter, or propagules left behind by the prior community. Unlike primary succession, secondary succession is characterized by a more rapid process of ecosystem recovery.
Example of secondary succession :
After a forest fire, secondary succession occurs as the scorched landscape undergoes renewal. Pioneer species, including grasses and herbaceous plants, swiftly colonize the barren soil, stabilizing it and initiating the recovery process. As these early plants establish, they create conditions conducive to the growth of more complex vegetation, such as shrubs and young trees.
Sere : the entire sequence of communities that successively change in a given area is called sere. The name of sere depends on where the succession occurs or takes place. Different types of seres are as follows :