Types of biotic interactions of organisms in modern agroecosystems

How living organisms affect each other in an agrocenosis

Any crop in a field or greenhouse lives surrounded by hundreds of other organisms — from weeds and insects to soil bacteria and fungi. Their interaction directly affects the future harvest. All these relationships are divided into two main groups: topical (cohabitation in the same area) and trophic (feeding).

Topical relationships determine how organisms share space. This can be either simple mechanical damage (the whipping of tree branches) or the use of a neighbor as a support — for example, when a bindweed twines around the stem of a crop, or mosses and lichens settle on the bark. Birds also use trees as a substrate for nesting. In the microworld, topical relationships turn into antagonism: some microorganisms suppress others by secreting natural antibiotics like penicillin or streptomycin. On a global scale, such interactions can completely change the environment, turning a lake into a swamp.

Trophic relationships are based on the food chain. Plants act as producers — they create organic matter and store energy. They are consumed by primary consumers (herbivores), which themselves become food for secondary and tertiary consumers (predators that use animal proteins). All waste and residues at each level are decomposed by decomposers, returning mineral substances and carbon dioxide back to the producers.

In addition to direct consumption (predation, which occurs among vertebrates, insects, worms, mollusks, protozoa, bacteria, and plants) and mutually beneficial cooperation, other types of contact are distinguished in nature. To control the phytosanitary situation, it is important for an agronomist to distinguish between the following forms of cohabitation:

• Parasitism — permanent (true) or temporary (periodic) use of the host by a parasite as a source of food and habitat;
• Commensalism — cohabitation in which one species benefits (for example, small crustaceans on the skin of whales finding shelter and food), while the other is neither harmed nor benefited;
• Phoresy — the transport of some organisms by others (for example, remora fish);
• Synoecy — the use of someone else's burrows, nests, or structures;
• Neutralism — cohabitation of species in which they do not affect each other in any way;
• Amensalism — the suppression of the vital activity of one species in the presence of another.

Anthropogenic factor: managing the development of agroecosystems

With the advent of agriculture about 12 thousand years ago, natural processes began to be influenced by the anthropogenic factor — purposeful human activity. Primitive people were little different from ordinary omnivorous consumers, gathering what was ready in the wild. With the development of technology, the use of fire, and population growth, this influence turned into the main force changing biocenoses.

In the wild, the dispersal of plants occurs through plumes, the attachment of seeds to the fur of animals, or thanks to fleshy fruits and nuts that attract distributors. Reproduction depends on natural factors — pollination by wind or insects, sexual selection in animals, and parental care. In agrocenoses, humans replace these mechanisms with artificial ones. We select productive species, protect them from competition with weeds, destroy pests, and provide them with additional nutrients.

In livestock production, the anthropogenic factor works similarly. Humans have domesticated wild species, conduct continuous breeding work, and protect herds from predators. Livestock animals receive balanced feed for rapid growth and development. As a result, natural selection in agriculture is almost completely replaced by artificial control.

Limits of sustainability of agroecosystems and principles of environmental control

The development of technologies and production methods has allowed humans to temporarily overcome the effect of traditional limiting factors and increase their population by tens of thousands of times. However, the creation of one's own anthropoecosystem does not mean that fundamental ecological laws have ceased to operate. On a biosphere scale, uncontrolled economic activity proves to be destructive, which is why there are practically no ecosystems left on the planet that have not experienced anthropogenic impact.

It is impossible to completely refuse the use of natural resources, so in practical work, it is necessary to strictly control the degree of impact on the environment. It is important to consider that natural mechanisms are extremely sensitive to any deviations from the norm. Intensive exploitation of soil, water, and energy resources while ignoring ecological limits leads to rapid degradation of the habitat.

Modern trends in the development of economic activity are accompanied by a complex disruption of the natural balance. Changes in environmental conditions occur both at the global level and on the scale of specific agro-ecosystems. The main factors of degradation of natural ecosystems include:

• global atmospheric and climatic shifts: climate warming due to the intake of carbon dioxide from burning fuel, acid rain, and the destruction of the ozone layer;
• depletion and pollution of basic resources: drastic environmental changes due to soil and water body pollution, as well as irrational water consumption;
• disruption of the structure of biocenoses: extermination of various animal and plant species, as well as accidental or intentional introduction of species from one ecosystem to another.

Currently, the anthropo-ecosystem is in a stage of rapid growth and maintains its existence through the active exploitation of natural reserves. The depletion of soil, water, and energy resources creates risks of social conflicts and the destruction of existing civilization. An alternative path is the transition to sustainable development, which requires the mandatory recognition of natural limits.

The concept of sustainable development involves implementing measures that limit the negative impact on the biosphere and prevent the depletion of resources. The first practical steps in this direction are already being taken at the international and state levels. These include:

• strict control over environmental pollution;
• creation of protected areas to preserve biodiversity;
• family planning and regulation of natural resource management.