During the course of the succession, the face of the community is constantly changing. The functioning of the ecosystem is also changing.
Changes in energy indicators in the process of succession
Succession would be impossible if the gross production of producers was equal to the energy consumption of all organisms in the ecosystem (the total respiration of the community).
It is clear that in such an ideal case, the production processes are balanced by the respiration processes. Consequently, the biomass of organisms in such a system remains constant, and the system itself remains unchanged, or equilibrium.
If the “total respiration” is less than the gross primary production, the accumulation of organic matter will occur in the ecosystem, if it is greater, it will decrease. If an excess of some resource appears in the system, then organisms that can use it are sure to be found. If the resource turns out to be insufficient, then some of the organisms will die. In both cases, a change in the biocenosis will occur.
These changes are the basis of ecological succession.
The succession goes in the direction of a shift in the flow of energy towards an increase in its amount, aimed at maintaining the system, and the ecosystem tends to form the highest biomass with the lowest biological productivity.
It has been proven that successions are accompanied by an increase in productivity up to the climax community, in which energy conversion occurs most efficiently.
With the transition to a climax community, a decrease in overall productivity usually occurs. Thus, productivity in old forests is lower than in young ones, which, in turn, may have lower productivity than previous layers of herbaceous plants richer in species.
As the succession progresses, an increasing proportion of available nutrients accumulates in the community biomass, and, accordingly, their content in the abiotic component of the ecosystem (soil or water) decreases. The amount of detritus formed also increases. The main primary consumers are not herbivores, but detritivores. Corresponding changes are also taking place in food webs. Detritus becomes the main source of nutrients.
In the course of succession, the closedness of biogeochemical cycles of substances increases (about the cycles of substances, see the section “Biosphere”).
A mature community with its great diversity and abundance of organisms, developed trophic structure and balanced energy flows is able to withstand changes in physical factors (for example, temperature, humidity) and even some types of chemical pollution to a much greater extent than a young community.
However, the young community is capable of producing new biomass in much larger quantities than the old one. Indeed, in a mature community at the stage of stability and stability, the net finished product is spent mainly on the “common respiration” of plants and animals and may even be zero.
Meaning for a person
On the one hand, a person can harvest a rich harvest in the form of pure products, artificially supporting a young community.
On the other hand (from the point of view of a person), the stability of a mature community, its ability to withstand the effects of physical factors (and even manage them) is a very important and highly desirable property.
People, often in pursuit of economic gain, do not think about the consequences of environmental violations. This is partly due to the fact that even environmental specialists cannot yet give accurate predictions of the consequences of various disturbances in mature ecosystems.
Nevertheless, even the knowledge that has been accumulated by ecology at the present time is enough to be sure that the transformation of our biosphere into one vast carpet of arable land is fraught with great danger. For our own protection, certain landscapes must be represented by natural communities.