All environmental factors characterizing environmental conditions are divided into two main groups - abiotic (they include climatic and soil) and biotic factors (zoogenic and phytogenic). Together they are combined into an animal habitat or plant growth.
Environmental factors
Depending on the characteristics of their influence on animals and plants, they are divided into the following main groups:
1) climatic, including features of the light and thermal regime, moisture level and air quality;
2) soil-ground, which characterize the quality of nutrition received by plants depending on the type of soil, parent rock and groundwater;
3) topographic, acting indirectly, since climate and soil quality depend on the relief of the habitat of living organisms;
4) biotic: phytogenic, zoogenic and microgenic factors;
5) anthropogenic, including all types of human impact on the environment.
It is worth noting that all these groups of factors act not individually, but in combination with each other. Because of this change in indicators, at least one of them will lead toimbalance in this complex. For example, an increase in temperature is associated with an increase in air humidity, the gas composition of the air changes, the soil dries up, photosynthesis increases, etc. However, the organisms themselves are able to influence these environmental conditions.
Biotic factors
Biota is a living component of the cenosis, including not only plants and animals, but also microorganisms. Each of these living organisms exists in a certain biocenosis and closely interacts not only with its own kind, but also with representatives of other species. All of them affect the living beings around them, but also receive a response from them. Such interactions can be negative, positive, or neutral.
The totality of interactions with each other and with the inanimate part of the environment is called biotic environmental factors. These include:
- Phytogenic factors are the effects that plants have on themselves, other plants and animals.
- Zoogenic factors are the influence exerted by animals on themselves, other animals and plants.
The influence of certain biotic factors at the ecosystem level determines the features of the transformation of substances and energies, namely their direction, intensity and nature.
Phytogenic factors
Relationships of plants in communities with the suggestion of Academician V. N. Sukachev began to be called co-actions. He identified three categories in them:
1. Direct (contact) coactions. In this group he included directinfluence of plants on organisms in contact with them. These include the mechanical and physiological effects of plants on each other. An example of this phytogenic factor - direct interaction between plants - is the damage to the tops of the crowns of young coniferous trees by whipping them with flexible branches of closely spaced neighboring hardwoods. Or, for example, close contact of the root systems of various plants. Also, direct phytogenic environmental factors include competition, epiphytism, parasitism, saprophytism and mutualism.
2. Indirect co-actions of a transabiotic nature. The way plants influence the organisms around them is to change the physicochemical characteristics of their habitats. Many plants are edificators. They have an environmental impact on other plants. An example of such a phytogenic biotic factor is the weakening of the intensity of sunlight penetrating the vegetation cover, which means a change in the seasonal rhythm of lighting, temperature in the forest, and much more.
3. Indirect coactions of a transbiotic nature. Plants influence the environment indirectly, through other organisms, such as bacteria. It is known that special nodule bacteria settle on the roots of most legumes. They are able to fix free nitrogen by converting it into nitrites and nitrates, which, in turn, are easily absorbed by the roots of almost any plant. Thus, leguminous plants indirectly increase soil fertility for other plants, acting through an intermediary -nodule bacteria. Also, as an example of this phytogenic environmental factor, one can name the eating by animals of plants of certain groups, which leads to a change in the numerical ratio of species. As a result of the elimination of competition, uneaten plants begin to grow stronger and have a greater impact on neighboring organisms.
Examples
Competition is one of the main factors in the formation of biocenoses. Only individuals survive in them, which turned out to be more adapted to certain environmental conditions and managed to develop the organs involved in nutrition earlier than others, captured a large area, and found themselves in better lighting conditions. In the course of natural selection, individuals weakened in the process of competition are destroyed.
When a cenosis is formed, many characteristics of the environment change, caused by the expenditure of material and energy resources, as well as the emission of waste products of organisms in the form of chemical compounds, fallen leaves and much more. This process of direct or indirect influence of plants on neighbors due to saturation with environmental substances is called allelopathy.
Also in phyto- and biocenoses, symbiosis is widely found, manifested in the mutually beneficial relationship of woody plants with fungi. Such a phytogenic factor is typical for legumes, willows, suckers, beech and other woody plants. Mycorrhiza appears on their roots, which allows plants to receive mineral s alts of the soil dissolved in water, and fungi, inin turn, gain access to organic matter.
It is also worth noting the role of microorganisms that decompose litter, converting it into mineral compounds, and also assimilate nitrogen from the air. A large category of microorganisms (such as fungi and bacteria) parasitizes trees, which, with their massive development, can cause irreparable harm not only to the plants themselves, but also to the biocenosis as a whole.
Classification of interactions
1. By subjects. Depending on the number of plants that affect the environment, as well as the number of organisms subject to this influence, they distinguish:
- Individual interactions that are carried out by one plant per living organism.
- Collective interactions, which include the relationship of groups of plants with each other or with individual individuals.
2. By means of influence. According to the type of direct or indirect influence exerted by plants, phytogenic environmental factors are:
- Mechanical, when interactions are characterized by a change in the spatial position of the body and are accompanied by contact or pressure of various parts of the plant on neighboring organisms.
- Physical, when talking about the effect of weak electric fields generated by plants on their ability to distribute soil solutions between nearby plants. This is because between the small sucking roots there is a certain difference in electrical potentials, which affectsthe intensity of the process of absorption of ions from the soil.
- Ecological, representing the main phytogenic factors. They manifest themselves in the transformation of the entire environment under the influence of plants or only some part of it. But at the same time, they do not have a specific character, this influence does not differ from the influence of inanimate objects.
- Cenotic, characteristic exclusively of living organisms (plants and animals) characterized by activity. An example of a phytogenic factor is the simultaneous consumption by neighboring plants of certain nutrients from one source, and in case of their deficiency, a certain distribution of chemical compounds between plants is included.
- Chemical, also called allelopathy. They manifest themselves in the inhibition or stimulation of the basic life processes by chemicals released during the life of plants (or when they die). Importantly, they are not animal or plant foods.
- Information-biological, when genetic information is transferred.
3. By the participation of the environment. According to this feature, phytogenic factors are divided into:
- Direct, including all mechanical interactions, such as interlacing and fusion of roots.
- Topical, reduced to the transformation or creation by plants of any elements of the environment (light, nutrition, heat, etc.).
4. According to the role of the environment in obtaining nutrition, there are:
- Trophic,consisting in a change under the influence of plants in the quantity or composition of substances, their state.
- Situational, which indirectly affect the quality and quantity of food received. So, an example of a phytogenic factor is the ability of some plants to change the pH of the soil, which affects the absorption of nutrients from it by other organisms.
5. By the consequences. Depending on how the vital activity of plants will affect neighboring plants, they distinguish:
- Competition and mutual restriction.
- Adaptation.
- Elimination, which is the most important form of interaction between plants during changes in their communities.
- Prevention, manifested in the creation by one plant species of unfavorable phytogenic environmental factors for the development of other species at the stage of seed germination or primordia, which leads to the death of seedlings.
- Self-limitation that occurs in the phase of intensive growth of plant organisms. It comes down to the active transfer of mineral nutrients from inaccessible forms to available ones, but their consumption by plants lags behind this process in speed. This leads to a delay or cessation of their growth.
- Self-favoring, which is the ability of plants to change the environment for themselves. Such phytogenic factors and their characteristics determine the state of any biotope, such as pine stands, in moss synusias.
It is worth noting that the same impact, according to different features of this classification, can be attributed to different types. So, the competitionthe consequence of the interaction is also trophic, topical, coenotic and individual.
Competition
The concept of competition in biological science has received attention for more than a dozen years. Its interpretation was vague or, on the contrary, too narrow.
Today, competition is understood as such interactions in which a limited amount of food is distributed disproportionately to the needs of interacting organisms. As a result of direct interactions, phytogenic factors lead to the fact that plants with large requirements receive larger amounts of nutrition than would be the case with proportional distribution. There is competition when using the same power source at the same time.
It is convenient to consider the mechanism of competitive relations on the example of the interaction of three trees feeding from the same source. The resources of the environment have a shortage of the substances they need. After some time, the growth of two of them decreases (oppressed trees), in the third it increases with constant rates (the dominant plant). But this situation does not take into account the possibility of the same needs of neighboring trees, which would not lead to a difference in growth.
In reality, environment resources are unstable for the following reasons:
- exploring space;
- climatic conditions are changing.
The vital activity of a tree can be quite expressed by the ratio of three quantities:
- needs - the maximum of substances and energy that a plant can take;
- the minimum required forhis life;
- real nutrition level.
With increasing size, the level of needs, at least, increases before aging. The actual level of nutrition received by trees depends on many factors, including "social relations" in the cenosis. Oppressed trees receive the minimum amount of nutrients, which is the reason for their elimination. The dominant specimens depend to a lesser extent on the coenotic setting. And the growth depends on the conditions of the abiotic environment.
Over time, the number of trees per unit area decreases and the ratio of coenotic classes changes: the proportion of dominant trees increases. This results in a mature forest dominated by dominant trees.
So, competition as a phytogenic factor of direct interaction between organisms can be represented as a process of uneven distribution of resources, characterized by a mismatch of needs, which leads to the division of plants into different coenotic groups and to the death of the oppressed.
Mutual restriction differs from competition in the proportional distribution of the nutrient resources of the environment. Although many researchers attribute it to one of the types of competition - symmetrical. Such interaction occurs between individuals with approximately equal competitive abilities of the same or different species.
Rise of competition
Competition between plants can only occur if the following conditions are met:
- qualitative and quantitative similarityneeds;
- shared consumption of resources from a common source;
- existing shortage of environmental resources.
Obviously, with an excess of resources, the needs of each plant are fully satisfied, which does not apply to phytogenic factors. However, in the opposite case, and even with joint nutrition, the struggle for existence begins. If the active roots of plants are in the same soil layer and are in contact with each other, it is difficult to judge the uniform distribution of nutrients. If the roots or crowns are located in different layers, then nutrition is not considered simultaneous (it is sequential), which means that we cannot talk about competition.
Examples of competition between plants
Competition can come for light, for soil nutrients and for pollinating insects. It can be influenced not only by the nutrients themselves, but also by many phytogenic factors. An example is the formation of dense thickets on soils in which there is a lot of mineral nutrition and moisture. The main struggle in this case is for light. But on poor soils, usually each plant receives the necessary amount of ultraviolet rays, and the struggle is for soil resources.
The result of intraspecific competition is the distribution of trees of the same species into Craft classes. According to their power, plants can refer to:
- I class, if they are dominant, have a thick trunk and thick branches from the base of the trunk, have a spreading crown. They enjoysufficient influx of the sun and extract huge amounts of water and nutrients from the soil due to the developed root system. Found singly in the forest.
- II class, if they are also dominant, the highest, but with a smaller trunk diameter and a slightly less powerful crown.
- III class, if they are smaller than the previous class, but still have a top open to the sun's rays. They also dominate in the forest and, along with class II, form the bulk of the trees.
- IV class, if the trees are thin, small, do not receive direct sunlight.
- V class if the trees are dying or already dead.
Competition for pollinators is also important for plants, where the species that best attracts insects wins. More nectar or sweetness can be an advantage.
Adaptive Interactions
They manifest themselves in the fact that phytogenic factors that transform the environment make its properties acceptable for acceptor plants. Most often, the change occurs insignificantly, and they are fully manifested only when the influencing species is a powerful edificator, and it must be presented in the full range of development.
One form of mechanical contact is the use by one organism of another plant as a substrate. This phenomenon is called epiphytism. About 10% of all types of plant organisms are epiphytes. The ecological meaning of this phenomenon consists in a kind of adaptation to the light regime in conditions of dense tropicalforests: epiphytes get the opportunity to get to the light rays without significant growth costs.
Physiological contacts of various plants include parasitism and saprotrophism, which also applies to phytogenic factors. Do not forget about mutualism, an example of which is the symbiosis of fungal mycelium and plant roots. Despite the fact that fungi receive carbohydrates from plants, their hyphae increase the absorptive surface of the root tenfold.
Connection forms
All kinds of mechanisms of both positive and negative interactions between different living organisms themselves can be very subtle and non-obvious. Relatively recently, a group of scientists studied in detail the effects of plants on the environment with the help of lifetime elimination of complex organic substances that have a protective function into the environment. Such relationships between plants are called allelopathic. They significantly affect the size of the obtained bioproducts of plants (not only cultivated, but also wild ones), and also determine the best ways to rotate crops in garden plantings (for example, an apple tree develops better after currants or raspberries, plums are best planted in those places where used to grow pears or peaches).
The main forms of connections between plants and animals in biocenoses, according to V. N. Beklemishev, are:
- Topical connections that arise due to the fact that one or more organisms change the environment of others in a favorable direction. For example, sphagnum mosses tend to acidify the soil solution, which creates favorable conditions for sundew and cranberries in swamps.
- Trophic connections, which consist in the fact that representatives of one species use an individual of another species, its waste products or leftovers as a food source. Thanks to trophic links, storks enter wetland cenoses, and elks usually settle in aspen forests.
- Factory bonds that occur when individuals of some species use members of other species to build their nests or dwellings. For example, trees provide birds with hollows or branches for building nests.
