The influence of abiotic factors on the productivity and vital activity of organisms

The spread of organisms from one ecosystem to another and from one part of an ecosystem to another is determined by various factors. For ecology, the reaction of organisms to environmental factors is of interest. The influence of factors on living things is characterized by certain quantitative and qualitative patterns.

For different species, the conditions in which they thrive best are not the same. For example, some plants prefer very moist soil, others relatively dry. Some require high temperatures, while others tolerate lower ones better.

Let us denote the set of values of any factor as a vector, or scale. Life is possible only within certain values of factors, the totality of which is called the ecological spectrum. Each species is characterized by its own ecological spectrum.

The action of each factor is characterized by the presence of three zones within its general spectrum:

1) a zone of impaired vital activity due to a lack of the factor (minimum zone);

2) a zone of normal vital activity (optimum zone);

3) a zone of impaired vital activity due to an excess of the factor (maximum zone).

At the minimum and maximum of a factor, an organism can live, but does not thrive (stress zones). The entire range of values of a factor from the minimum to the maximum at which an organism's vital activity is possible is called the range of tolerance.

In 1840, chemist Justus von Liebig, observing the effect of chemical fertilizer on plants, discovered that limiting the dose of any of them leads to slowed growth. This allowed the scientist to formulate a rule, which is called Liebig's Law of the Minimum.

According to this law, life possibilities are limited by factors whose quantity and quality are close to the minimum required by an organism or ecosystem.

The law applies to all biotic and abiotic factors influencing an organism and is applicable to plants, animals, and humans alike.

In 1913, American scientist Shelford showed that not only a substance present in a minimum can determine the viability of an organism, but that an excess of any element can also lead to undesirable deviations. For example, if there is a lack of water in the soil, the assimilation of mineral nutrients by the plant is hindered, but an excess of water also leads to rotting processes and soil acidification.

Factors present in either excess or deficiency (relative to the optimal requirements of the organism) are called limiting factors. Shelford's rule became known as the Law of the Limiting Factor or the Law of Tolerance.

Among the chemical and physical environmental factors, we distinguish three groups: climatic factors, soil cover factors, and aquatic environment factors.

I. M a i n c l i m a t i c f a c t o r s: 1. S o l a r r a d i a n t e n e r g y.

Infrared rays (wavelength greater than 0.76 µm) have predominant importance for life, accounting for 45% of all solar energy. In photosynthesis processes, ultraviolet rays (wavelength up to 0.4 µm), which make up 7% of solar radiation energy, play the most important role. The rest of the energy is in the visible part of the spectrum with a wavelength of 0.4 - 0.76 µm. 2. I l l u m i n a t i o n o f t h e e a r t h' s s u r f a c e.

It plays an important role for all living things, and organisms are physiologically adapted to the alternation of day and night. Virtually all animals have circadian activity rhythms associated with the cycle of day and night.

A t m o s p h e r i c h u m i d i t y.

It is associated with the saturation of air with water vapor. Up to 50% of all atmospheric moisture is concentrated in the lower layers of the atmosphere (up to 2 km in height).

The amount of water vapor in the air depends on air temperature. For a specific temperature, there is a certain limit of air saturation with water vapor, which is called the maximum. The difference between the maximum and current air saturation with water vapor is called humidity deficit (saturation deficit). Humidity deficit is an important ecological parameter as it characterizes two variables: temperature and humidity.

It is known that an increase in humidity deficit during certain periods of the growing season promotes increased plant fruiting, and in some insects leads to outbreaks of reproduction.

P r e c i p i t a t i o n.

Clouds and atmospheric precipitation are formed due to the condensation and crystallization of water vapor in the upper layers of the atmosphere. Dew and fog form in the surface layer.

Moisture is the primary factor determining the division of ecosystems into forest, steppe, and desert. An annual precipitation total below 1000 mm corresponds to a stress zone for many tree species, and the survival limit for most of them is about 750 mm/year. At the same time, for most grasses, this limit is significantly lower — approximately 250 mm/year, and cacti and other desert plants are capable of growing with 50 - 100 mm of precipitation per year. Accordingly, forests usually develop in areas with precipitation levels above 750 mm/year, grass steppes between 250 and 750 mm/year, and where there is even less, vegetation is represented by drought-tolerant crops: cacti, wormwood, and tumbleweed species. With intermediate annual precipitation values, transitional ecosystems develop (forest-steppes, semi-deserts, etc.).

The precipitation regime is a crucial factor determining the migration of pollutants in the biosphere. Precipitation is one of the links in the Earth's water cycle. 5. G a s c o m p o s i t i o n o f t h e a t m o s p h e r e.

It is relatively constant and includes primarily nitrogen and oxygen with an admixture of carbon dioxide, argon, and other gases. In addition, ozone is contained in the upper layers of the atmosphere. Solid and liquid particles are also present in the atmospheric air.

Climatic factors: temperature, precipitation, and air movement

The gas composition of the atmosphere and solar radiation directly determine the conditions for the growing season of agricultural crops. Nitrogen participates in the formation of protein structures, oxygen provides for oxidative processes, and carbon dioxide is necessary for photosynthesis and the retention of the Earth's thermal radiation. The ozone layer shields hard ultraviolet radiation, while solid and liquid suspended particles regulate atmospheric transparency. The volume of incoming heat is directly proportional to the sine of the Sun's angle above the horizon, which causes diurnal and seasonal temperature dynamics in a specific area.

• Normal atmospheric pressure — 101325 Pa (760 mm Hg)
• Precipitation threshold for forest ecosystems — from 750 mm/year
• Precipitation threshold for desert zones — less than 250 mm/year
• Silica (SiO2) content in the mineral part of the soil — over 50%

Temperature regime and precipitation volume are key indicators defining the type of ecosystem in a territory. With an annual precipitation sum of 750 mm and above, forest tracts are formed, and temperature determines their species composition. In cold regions with a short growing season and deep snow cover, spruce-fir stands predominate; in temperate latitudes, deciduous trees are common; and in the tropics without frosts, evergreen broad-leaved species dominate. In areas with less than 250 mm of precipitation per year, deserts are formed, the species composition of which strictly depends on the temperature zone.

The movement of air masses is caused by uneven heating of the Earth's surface and atmospheric pressure differentials. Wind directs air currents toward lower pressure and higher heat, regulating humidity and ensuring the transport of impurities in the surface layer. Permanent high and low-pressure areas with regular seasonal and diurnal minimums and maximums are formed across the globe.

Soil: structure, profile, and mineral composition

Soil is the upper loose layer of land formed during the transformation of the lithosphere under the influence of water, air, and living organisms. The main qualitative indicator of soil is its soil fertility, which directly depends on physical and chemical properties. The soil profile constantly develops a horizontal structure as substances move and transform. The top surface layer consists of litter or sod formed by dark-colored plant and organic residues of varying degrees of decomposition.

Below the litter lies the humus horizon A1 — a porous mixture of decomposed organic matter (humus), living organisms, and mineral particles, where the bulk of plant roots are concentrated. In forest soils, a light-colored podzolic horizon A2 with an unstable structure is located underneath, which is absent in chernozem, dark chestnut, and chestnut soil types. Deeper lies the dense illuvial horizon B of a brown color, which accumulates mineral and organic substances leached from above, beneath which lies the parent rock C.

The mineral portion of any soil horizon consists of more than 50% silica (SiO2), with the remainder occupied by alumina and oxides of iron, magnesium, potassium, phosphorus, and calcium. The incoming plant litter enriches the soil with carbohydrates, proteins, fats, resins, and tannins. During the process of soil formation, organic residues are either mineralized into simple compounds (water, carbon dioxide, ammonia) or humified, forming soil humus.

The mechanical composition of the soil — the ratio of sand, sandy loam, clay, and loam particles — determines the key physical conditions for the development of crops. Water permeability, moisture-holding capacity, density, and the thermal regime of the plot depend on it. Aeration is of particular importance — the saturation of the soil horizon with air, without which the normal respiration of the root system is impossible.

The reaction of the soil environment directly affects the availability of nutrients and the selection of crops for crop rotation. The flora of neutral soils is the most species-rich; however, plants possess varying levels of tolerance to acidity. For proper planting planning, one should be guided by the basic classification of soils according to the pH value.

Slightly acidic soils are optimally suited for growing wheat, peas, corn, and tomatoes. On very acidic soils, potatoes and berry crops show the best results. Planting crops without considering the reactivity of the environment leads to a harvest shortfall and reduced efficiency of fertilizers.

The physical and chemical characteristics of the soil are continuously formed by its living inhabitants: bacteria, algae, fungi, protozoa, worms, and arthropods. Earthworms, beetle larvae, and mites loosen the soil, increasing aeration and processing hard-to-decompose organic matter. Applied mineral fertilizers cannot be absorbed by plants directly — the soil microflora converts them into a biologically available form.

Abiotic factors of the aquatic environment

The aquatic environment occupies 71% of the Earth's surface area and acts as the main accumulator of solar energy due to its high heat capacity. The dynamics of temperature fluctuations in water are significantly lower than in the air, and the constant movement of water masses maintains a relatively homogeneous physical and chemical composition. At the same time, temperature stratification clearly manifests with increasing depth.

• Share of Earth's water space — 71%
• Excess of water density over air — 800 times
• Excess of water viscosity over air — approximately 55 times
• Limits of water temperature fluctuation — from -2 °C to +35–37 °C
• Salinity of ocean water — 35 g/l
• Salinity of the Black Sea — 19 g/l

The light regime under the surface is determined by the transparency of the water and its turbidity index. Photosynthesis of green bacteria, phytoplankton, and higher plants, which form the primary organic mass, depends on the amount of penetrating light. Turbidity increases with the ingress of suspended particles from wastewater, therefore this parameter is subject to strict industrial control.

The mineral composition of water bodies differs by chemical profile: in fresh waters, there are few salts and carbonates predominate; in the ocean (35 g/l), the Black Sea (19 g/l), and the Caspian Sea (about 14 g/l), chlorides and sulfates dominate. Increased consumption of dissolved oxygen for respiration and the oxidation of organic discharges makes the environment unsuitable for aerobic organisms. At the same time, any sharp shifts in pH or salinity lead to the mass death of hydrobionts adapted to the strict boundaries of their habitat.