Fundamentals of ecosystem theory and classification of environmental factors

The environment is a system of interconnected natural and anthropogenic objects and phenomena in which the work, daily life, and recreation of people take place.

An ecological system (ecosystem) is an interconnected, unified functional collection of organisms and their habitat.

Examples of ecosystems include a pond with plants and living organisms, or a forest with its inhabitants. Similar organisms living in different environmental conditions form different ecosystems. For example, a spruce forest in the Tomsk region and one in the Caucasus Mountains are different ecosystems.

To denote natural biosystems occupying a specific territory, V.N. Sukachev proposed the term biogeocenosis (from "bios" meaning life, "geo" meaning Earth, and "cenosis" meaning community).

The concepts of ecosystem and biogeocenosis are close, but they are not synonyms. Ecosystems are dimensionless, stable systems of living and non-living components in which the circulation of substances and energy occurs. Thus, an ecosystem can be a drop of water with its microbial population, a forest, a flower pot, or a manned spacecraft. The concept of an ecosystem is broader than that of a biogeocenosis, i.e., any biocenosis is an ecological system, but not every ecosystem can be considered a biogeocenosis; furthermore, a biogeocenosis is strictly a terrestrial formation with distinct boundaries.

An ecosystem includes two main components: the biocenosis — a collection of living organisms, and the biotope (from the Greek "topos" meaning place) — the living space of the biocenosis. Representatives of individual plant or animal species living in a given ecosystem form populations of these species. For example, the collection of hares forms a population of hares, the collection of birches forms a population of birches, etc.

As we will see further, anthropogenic activity is always directed at the biogeocenosis (ecosystems), outside of which there is no life on Earth. The biogeocenosis is an elementary structural unit of the biosphere, complexly organized and developing according to specific laws, and it is with this that humans interact.

The environment surrounding an organism is characterized by enormous diversity, consisting of a multitude of elements, phenomena, and conditions that are dynamic in time and space, which are considered as factors.

From an ecological perspective, the environment consists of natural bodies and phenomena with which an organism is in direct or indirect relationships. The environment surrounding an organism is characterized by enormous diversity, consisting of a multitude of elements, phenomena, and conditions that are dynamic in time and space, which are considered as factors.

An ecological factor is any element of the environment capable of exerting a direct influence on living organisms and on the nature of their relationships with one another. In turn, an organism responds to an ecological factor with specific adaptive reactions.

Ecological environmental factors associated with any organism are divided into categories: 1) abiotic factors (factors of non-living nature); 2) biotic factors (factors of living nature).

Anthropogenic impact on ecological factors

Human impact on the environment manifests itself primarily in changing the regime of a multitude of biotic and abiotic factors, often beyond the limits that meet the ecological requirements of living organisms. Any living organism does not require temperature, humidity, mineral and organic nutrients, or any other factors in general, but rather a specific regime for them; that is, there are certain upper and lower bounds to the amplitude of permissible fluctuations of these factors. The wider the limit of a factor, the higher the stability, i.e., the tolerance of the given organism.

The requirements of a particular organism for environmental factors determine the boundaries of its distribution (range) and the place it occupies in the ecosystem. The set of multiple environmental parameters that define the existence conditions of a particular species, along with its functional characteristics (its energy conversion, information exchange with the environment and its own kind, etc.), constitutes an ecological niche.

Concept and characteristics of an ecological niche

An ecological niche is an abstract concept; this term reflects the role that a specific species of organisms plays in a biogeocenosis. To characterize an ecological niche, it is necessary to know the following parameters:

• what the organism feeds on;
• what preys on it;
• the organism's ability to move through space;
• which "floor" (level) in the biogeocenosis it occupies;
• other features of its interaction with the living and non-living elements of the biogeocenosis.

An ecological niche characterizes the environmental conditions of the organisms' vital activity, which are determined by both abiotic and biotic factors.

Consequently, in every biogeocenosis, all species of living organisms occupy specific ecological niches, spreading out in such a way as to use all energy and material resources as fully and effectively as possible without interfering with one another. Some species of living organisms spread out in the upper levels, consuming solar energy, extracting necessary nutrients from atmospheric air, and utilizing atmospheric humidity. Others settle in the soil and live off the energy resources of dead organic matter, soil moisture, and gases contained in soil pores. By spreading out in this manner, all living organisms, being in close interaction, ensure each other's existence and a constant circulation of substances. The completeness and speed of the circulation of substances in a specific biogeocenosis will depend on the diversity of living organisms and the number of ecological niches.

As we will see further, the existence and development of ecological systems depend on the amount of energy entering the ecological system, the rate of its transfer through individual elements of the system, and the intensity of the circulation of mineral nutrients.

Energy foundations of the functioning of natural systems

As is known, energy is a single measure of various forms of motion. To quantitatively characterize qualitatively different forms of motion, corresponding types of energy are introduced:

• mechanical;
• internal;
• electromagnetic;
• chemical;
• nuclear, etc.

Living beings are unique natural objects capable of capturing energy coming from Space primarily in the form of sunlight, retaining it in the form of energy of complex organic compounds, transferring it to each other, and transforming it into mechanical, electrical, and other types of energy. And all this corresponds to the law of conservation and transformation of energy (the 1st law of thermodynamics), according to which energy is neither created nor destroyed; it only changes from one form to another or is transferred from one body to another, while its total value remains constant.

Thermodynamic laws and the stability of biosystems

The second law of thermodynamics states that any action related to energy transformation cannot occur without its loss in the form of heat dissipated in space. In other words, the energy of any system tends toward a state called thermodynamic equilibrium, which is equivalent to maximum entropy.

Entropy, therefore, reflects the possibilities of energy transformation and is considered a measure of the system's disorder. Thus, a part of the energy entering an ecological system is lost and cannot perform work. For the entropy of a system not to increase, and for life to exist, an external source of energy is necessary — solar radiation.