Succession is ... Succession is primary and secondary. Examples of succession

Succession is an irreversible change in one biocenosis, the appearance of another. It can be caused by some natural phenomena or occurs under the influence of man. Ecological succession was originally explored by representatives of such a science as geobotany. In the future, this phenomenon became a subject of interest and other environmentalists. Pioneers, who revealed the importance of succession, were F. Clements, V. N. Sukachev, S. M. Razumovsky. Next, we will analyze the concept in more detail, we give a classification. In addition, the article will describe the progress of the process using examples.

Terminology

Who introduced the definition? Directly the concept of "succession" was proposed by F. Clements to determine the successive special biological communities replacing each other in time. They are characterized by the formation of a series or series so that the preceding creates conditions for the development of the next. In the event that there are no factors capable of provoking another succession, the series ends with a relatively stable community that is characterized by a constant exchange. The education described above was defined by Clements using the special term "climax". According to the scientist, this is a stable community, within which there are no factors that contribute to any changes in its development. In this case, the duration of the menopause is not important.

Classification

Successions can be ordered for different reasons. With the help of classification on various grounds, various types of successions can be singled out. Among such signs: the rate of formation / damping, the duration of existence, reversibility, constancy, origin, the tendency of development (progress or degradation), change in the number and diversity of species. Classify the succession can be for a variety of reasons. The process of grouping depends primarily on what the scientist is trying to achieve. At the same time, there are types of successions, grouped by the nature of the processes taking place in a given stable community. On this basis, scientists identify two main categories: endogenous and exogenous. What is the difference? Endogenous succession is a change due to the activities of the communities themselves. The primary cause of the process is usually the imbalance in the exchange. In other words, the change is due to the activity of internal factors. Exogenous succession is a change provoked by external factors.

Microbiology

In the forest litter, for example, it is possible to investigate the succession in several stages simultaneously. This possibility is due to a shift in the direction from top to bottom when moving. In addition, the phenomenon can cause changes in humidity, the content of any special compounds or gases, temperature, etc. The process of soil formation is accompanied by a sufficiently long change in both the plant and microbial community.

Succession primary and secondary

What do these concepts mean? We will analyze further. Primary succession is characterized by the fact that it proceeds on a lifeless terrain. It can be a bare rock without vegetation, sandy areas, frozen lava and the like. When organisms begin to colonize such territories, their metabolism affects the environment and changes it. Then begins a more complex development. And then the species begin to change each other. An example of succession is the formation of the original soil cover, the settlement of an initially lifeless sandy territory, primarily microorganisms, plants, and then mushrooms and animals. A special role here is played by plant remains and substances formed as a result of organic decomposition. Thus, soil begins to form and change, microclimate changes under the influence of microorganisms, plants and fungi. As a result, the community of organisms is expanding. This succession is an ecogenetic change. It is called so because it changes the very territory on which it exists. And the initial occurrence of soil on a lifeless terrain is called the syngenetic shift.

Substrate moisture

This indicator influences the type of succession. So, the following groups are distinguished:

1. Xerarch, on anhydrous substrate.
2. Psammkseroseriya, on the sands.
3. Litoseroseriya, on the rocky terrain.
4. Geoxeroseries, on dry clay or loam.
5. Mesarch, if the substrate has a rather significant moisture content.
6. Hydrarchic if the substrate is extremely wet.

Primary successions take place in several stages. You can give interesting examples of succession. For example, in the forest zone, the lifeless and dry substrate is replaced first by lichens, then by moss, then herbage grows (annual plants), after them perennial shrubs, trees, grasses begin to develop. There are other examples of succession. So, it is often mentioned the settling of the territory of solidified lava after eruptions or slope after an avalanche.

Process Flow

The development of primary succession occurs simultaneously with soil formation. The influence on the process is externally affected by seeds, the dying of seedlings that are unstable to extreme conditions and (with certain time) interspecific competition. This or that community develops or is replaced mainly in connection with the difference in the nitrogen content in the soil and the degree of destruction of its mineral part. In the soil and other natural microbial communities, succession is a phenomenon usually caused by the receipt of a certain portion of the organic compound in one form or another. Since microorganisms adapt either to the destruction of different complex polymers, or to the absorption of any monomers at a high concentration, or to the existence under severe conditions of hunger, structural changes in the community are observed during the destruction and during the use of organic matter.

Secondary successions

These processes lead to the settlement of the territory by species after some damage. For example, a forest, partially destroyed by fire. The territory on which it was previously located, has preserved the soil and seeds. The community of grasses is formed already literally next year. And then there are deciduous trees. Under the cover of aspen or birch wood, spruce begins to grow, displacing later deciduous breeds. The restoration of dark coniferous trees takes about 100 years. But the forest in some areas is again being cut down. In this regard, in such areas, recovery does not occur.

Continualism and Structuralism in the Study of Biological Communities

Despite the fact that the definitions that Clements postulated apply in science everywhere, there are two paradigms that differ significantly from each other. Let us consider them in more detail. Within each of these paradigms, the meaning of Clements' definitions is different. What is the difference between these approaches? The followers of the paradigm of structuralism strongly support the conclusions of Clements and continue the development of his theory. Continualists, on the contrary, do not agree with the actual existence of such phenomena as biological communities, successions, menopause, post-climax, climax-continuum. In the last paradigm, ecosystem processes are reduced to the interaction of various categories among themselves. These species, according to continuum, accidentally begin to interact with each other and with inanimate nature. How did continuumality appear? The fact is that there is no one author of this theory: this paradigm was born almost simultaneously in two countries, in two independent scientific communities: from LG Ramensky in the USSR and G. Gleason in the USA.

The role of successions in the formation and change of the biosphere

Thanks to successions, the study of which continues in geobotanics to this day, the formation of the soil cover, the change in its composition, the settling of once lifeless areas first by microorganisms, and then by plants, fungi and animals. The study of the schemes and mechanisms by which both primary and secondary changes of communities take place clearly shows that it is impossible to predict in advance which species will replace each other in the chain. Nevertheless, the replacement of biological communities often occurs in such a way that the biological diversity in the studied territory increases.