Phytogenic factors and their features

All environmental factors characterizing environmental conditions are divided into two main groups - abiotic (they include climatic and soil) and biotic factors (zoogenic and phytogenic). All together they are combined into the habitat of animals 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 the features of light and thermal conditions, moisture level and air quality;

2) soil-soil, which characterize the quality of food received by plants, depending on the type of soil, parent rock and groundwater;

3) topographic, acting indirectly, since the climate and soil quality depend on the relief of the habitat of living organisms;

4) biotic: phytogenic, zoogenic and microbogenic factors;

5) anthropogenic, including all types of human impact on the environment.

It is worth noting that all these groups of factors do not act individually, but in combination with each other. Because of this change in indicators of at least one of them, it will lead to an imbalance 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 is drained, photosynthesis is enhanced, etc. However, the organisms themselves are able to influence these environmental conditions.

Biotic factors

Biota is a living component of 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 their own kind, but also with representatives of other species. All of them affect living creatures 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:

1. Phytogenic factors - this is the effect exerted by plants on themselves, other plants and animals.
2. Zoogenic factors - this is the effect exerted by animals on themselves, other animals and plants.

The influence of certain biotic factors at the ecosystem level determines the characteristics of the conversion of substances and energies, namely their direction, intensity and nature.

Phytogenic factors

The relationship of plants in communities with the filing of Academician V.N. Sukachev began to be called coactions. He identified three categories in them:

1. Direct (contact) co-operation. In this group, he attributed the direct effects of plants on organisms in contact with them. These include the mechanical and physiological effects of plants on each other. As an example of this phytogenic factor - direct interaction between plants - damage to the tops of the crowns of young conifers can be cited when their flexible branches of closely spaced neighboring deciduous species are whipping them. Or, for example, close contact of the root systems of various plants. Direct phytogenic environmental factors include competition, epiphytism, parasitism, saprophytism and mutualism.

2. Indirect co-actions of a trans-biotic nature. The way the plants influence the organisms surrounding them is to change the physicochemical characteristics of their habitats. Many plants are edificators. They have a medium-forming effect on other plants. An example of such a phytogenic biotic factor is the weakening of the intensity of sunlight penetrating into the vegetation cover, which means a change in the seasonal rhythm of lighting, the temperature regime in the forest, and much more.

3. Indirect co-actions of a transbiotic nature. Plants affect the environment indirectly, through other organisms, such as bacteria. It is known that on the roots of most legumes special nodule bacteria settle. They are able to fix free nitrogen by converting it to nitrites and nitrates, which, in turn, are easily absorbed by the roots of almost any plant. Thus legumes indirectly increase soil fertility for other plants, acting through an intermediary - nodule bacteria. Also, as an example of this phytogenic environmental factor, animals can eat plants of certain groups, which leads to a change in the numerical ratio of species. As a result of elimination of competition, not eaten plants begin to grow stronger and have a greater effect on neighboring organisms.

Examples

Competition is one of the main factors in the formation of biocenoses. Only individuals survive in them who are more adapted in certain environmental conditions and manage to develop organs participating in nutrition earlier than others, capture a large area, find themselves in better lighting conditions. In the course of natural selection, individuals weakened in the process of competition are destroyed.

During the formation of any cenosis, a change in many environmental characteristics occurs, caused by the expenditure of material and energy resources, as well as the emission of vital 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 widespread, manifested in mutually beneficial relationships of woody plants with fungi. Such a phytogenic factor is characteristic of legumes, willow, sucker, beech and other woody plants. Mycorrhiza appears on their roots, which allows plants to obtain mineral salts of soil dissolved in water, and fungi, in turn, gain access to organic matter.

It is also worth noting the role of microorganisms that decompose litter, converting it to mineral compounds, and also assimilate nitrogen from the air. A large category of microorganisms (such as fungi and bacteria) parasitizes on trees, which, when they are massively developed, 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 on the number of organisms susceptible to this influence, they distinguish:

• Individual interactions that are carried out by one plant on one living organism.
• Collective interactions, which include the relationship of plant collectives with each other or with individual individuals.

2. By methods of exposure. 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 they talk about the influence 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 affects the 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 whole 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 effect does not differ from the influence of inanimate objects.
• Coenotic, characteristic exclusively of living organisms (plants and animals) characterized by activity. An example of a phytogenic factor can be called the simultaneous consumption by neighboring plants of certain nutrients from one source, and if they are deficient, a certain distribution of chemical compounds between plants is included.
• Chemical, also called allelopathy. They are manifested in the inhibition or stimulation of the basic vital processes by chemicals released during the life of plants (or during their death). It is important that they are not animal or plant foods.
• Information-biological, when there is a transfer of genetic information.

3. By the participation of the environment. On this basis, phytogenic factors are divided into:

• Direct, including all mechanical interactions, for example, weaving and fusion of roots.
• Topical, reduced to the transformation or creation by plants of any elements of the environment (light, nutrition, heat and more).

4. According to the role of the environment in obtaining nutrition, there are:

• Trophic, consisting in a change under the influence of plants the amount or composition of substances, their condition.
• 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. According to the consequences. Depending on how the vital activity of plants will affect neighboring plants, distinguish:

• Competition and mutual restriction.
• Device.
• Elimination, which is the most important form of plant interaction during changes in their communities.
• Prevention, manifested in the creation by one species of plants of unfavorable phytogenic environmental factors for the development of other species at the stage of germination of seeds or primordia, which leads to the death of seedlings.
• Self-restraint arising in the phase of intensive growth of plant organisms. It boils down to the active conversion of mineral nutrients from forms inaccessible to food into affordable, but their consumption by plants lags in speed from this process. This leads to a delay or termination of their growth.
• Self-favor, which is the ability of plants to change the environment for themselves. Such phytogenic factors and their features determine the state of a biotope, for example, pine stands, in moss synusias.

It is worth noting that the same effect on different grounds of this classification can be attributed to different types. Thus, competition as a consequence of interaction is also trophic, topical, coenotic and individual.

Competition

The concept of competition in biological science has been given attention for more than a dozen years. His interpretation was blurry 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 greater needs receive larger amounts of nutrition than would be the case with a 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 as an example of the interaction of three trees feeding from one source. Environmental resources are deficient in the substances they need. After some time, the growth of two of them decreases (oppressed trees), in the third - it increases with constant indicators (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, environmental resources are variable for the following reasons:

• space is being mastered;
• climatic conditions change.

The vital activity of a tree can be fully expressed by the ratio of three values:

• needs - the maximum of substances and energy that the plant can take;
• the minimum that is necessary for his life;
• real level of nutrition.

With increasing size, the level of needs, as well as a minimum, rises before aging. The actual level of nutrition received by trees depends on many factors, including “social relations” in the cenosis. Oppressed trees receive a minimum amount of nutrients, which is the reason for their elimination. The prevailing specimens are less dependent on the coenotic situation. And the increase 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 leads to the prevalence of dominant trees in the ripe forest.

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 an interaction appears between individuals with approximately equal competitive abilities of one or different species.

Emergence of competition

Competition between plants can occur only if the following conditions are met:

• qualitative and quantitative similarity of needs;
• joint consumption of resources from a common source;
• current scarcity 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, 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 consistent), which means that we can not talk about competition.

Examples of competition between plants

Competition can go for light, for soil nutrients, and for pollinating insects. Not only nutrients themselves can affect it, but also 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 gets the necessary amount of ultraviolet rays, and the struggle is for soil resources.

The result of intraspecific competition is the distribution of trees of one species into Kraft classes. By their power, plants can relate 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 use a sufficient influx of sun and extract huge quantities of water and nutrients from the soil thanks to a developed root system. They are 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.
• Grade III, if they are smaller than the previous class, but still have a peak open to sunlight. They also prevail in the forest and, along with the II class, 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 at the stage of dying off or are already dead.

Competition for pollinators is also important for plants, in it the species that best attracts insects wins. The advantage may be a larger amount of nectar or its sweetness.

Adaptive interactions

They are manifested in the fact that phytogenic factors transforming the environment make its properties acceptable for acceptor plants. Most often, a change occurs insignificantly, and in full measure they appear only when the acting species is a powerful edificator, and it must be presented in the full development range.

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 peculiar adaptation to the light regime in the conditions of dense tropical forests: epiphytes get the opportunity to get out into light rays without significant expenses for growth.

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 the mycelium of the fungus and the roots of plants. Despite the fact that fungi receive carbohydrates from plants, their hyphae increase the absorption surface of the root tenfold.

Communication forms

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The main forms of communication 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 have the property of acidifying the soil solution, which creates favorable conditions in the swamps for sundew and cranberries.
• Trophic relations, which consist in the fact that representatives of one species use an individual of another species, its metabolic products or residues as a food source. Thanks to trophic ties, storks enter wetland coenoses, and moose usually settle in aspen forests.
• Fabric relations arising when individuals of some species use representatives of other species to build their nests or dwellings. So, trees provide hollows or branches for birds to build nests.

• Foricheskie ties that arise due to the promotion of one species to the movement of individuals of another. Plants with juicy fruits settle more extensively due to the fact that animals provide them with the transportation of seeds.