The biological role of forests in nature

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

How often do we think about the role of forests in our life? What is a forest? What ecological functions does it perform? In this article we will try to answer these and many other questions related to the forest as a natural ecosystem.

The forest is a combination of woody, shrubby and herbaceous vegetation growing on the solid surface of the planet, including animals, microorganisms and other components of the natural environment (soil, water bodies and rivers, air envelope) biologically interconnected. The main properties of forests are the area and standing timber reserves. Forests grow on all continents except Antarctica and occupy about 31% of the land surface. The total area of the planet's forest fund is 4 billion hectares, and standing timber reserves are 527,203 million m3 [1].

A forest is a complexly organized self-regulating ecosystem in which the circulation of substances (nitrogen, phosphorus, oxygen, water, etc.) and energy flows between all types and forms of organisms are constantly carried out. All plants are adapted to each other, as well as to animal organisms, and vice versa, all animal organisms are adapted to plant organisms. They cannot exist without each other. Each forest area has a pronounced spatial structure (vertical and horizontal), which includes a large number of mature trees, shrubs, herbaceous plants, undergrowth of the main and accompanying species, as well as mosses and lichens.

The vertical structure of the forest is characterized by the distribution of different plant forms along the height, while the horizontal one reflects the distribution of different plant species in the horizontal plane. Along with a large number of plants, in the forest there are a huge number of different species without (c) vertebrates, millions of soil organisms, numerous insects, birds and animals. All of them together form an ecological system in which each plant and animal performs a specific ecological function, participating in the cycle of various chemical elements.

Under the influence of external environmental factors (light, temperature, moisture, wind, currents, various forms of intelligent human activity, etc.), certain changes occur in the forest ecosystem, which, as a rule, do not have a sharp and destructive nature, and do not lead to imbalance in the ecosystem. However, the strongly increasing impact of unreasonable human activity more and more often leads to a violation of the ecological balance, which is expressed in abrupt and catastrophic changes and consequences. So, in the summer of 2008 in the territory of Western Ukraine in the region of the Carpathian mountains, there was the largest flood due to numerous precipitations. As a result, about 40 thousand houses were flooded, almost 700 km of roads were washed out, more than three hundred bridges were destroyed [2].

One of the reasons for the large-scale flooding is the deforestation on the slopes of the Carpathian Mountains, when a significant part of the forest cover was cut down for almost 40 years [3].

The fact is that the forest plays an important water-regulating role, which is to slow down the surface runoff of melt and rainwater, transferring part of it to the ground, thereby reducing the destructive force of floods and floods, and thereby feeding groundwater. When rain falls, tree crowns and trunks retain some of the moisture, which allows water to be absorbed into the forest litter gradually, and not spontaneously. Forest litter retains moisture and, over time, gives it to rivers and groundwater, and some of the moisture is used to feed plants. In an open area (for example, a felling), rainwater entirely falls on the surface of the earth and does not have time to be absorbed, since the water permeability of the forest litter is higher than in an open area, which leads to the flow of most of the water from the surface into a depression or surface watercourse (stream, river). Sometimes an open area does not allow water to pass at all and it completely drains off, forming a powerful stream of water. The forest plays an important role in the distribution of winter precipitation and during thawing in spring. In open areas, the snow cover is fixed a little later than in the forest due to frequent thaws and is unevenly distributed due to the blowing winds. In forests, snow is distributed evenly, which is associated with a change in the wind regime in the surface layer. In general, more snow accumulates in open areas than in forests. In spring, under the influence of a powerful flow of solar radiation, snowmelt occurs, which depends not only on this factor. Various types of vegetation and relief play an important role in this process. An open area receives 100% of solar radiation, and only a part under the canopy of any tree stand, therefore, snow melts in forests more slowly. For example, in clearings, snow melts for 7-25 days, and in a spruce-fir forest for 32-51 days [4].

Domestic forest scientist Aleksandr Alekseevich Molchanov found that the coefficient of spring runoff sharply decreases with an increase in forest cover (from 0, 6-0, 9 on a treeless hilly area to a coefficient of 0, 09-0, 38 with a forest cover of 40%) [6].

When a forest is cut down, the tree canopy is removed and the soil loses its water permeability property, which leads to a violation of the water regime of watercourses, while the surface runoff increases and the process of soil destruction intensifies. Thus, the forest plays an important role in regulating the uniform flow of water into watercourses, participates in the water cycle, and prevents soil destruction.

An equally important property of vegetation is associated with the climate formation of the planet. The forest affects such climatic factors as wind, temperature, humidity, etc. Thanks to the wind, plants are pollinated, fruits and seeds spread, the process of evaporation of moisture from the leaf surface is enhanced, and the forest, in turn, reduces the wind speed in the surface air layer, regulating the temperature and humidity. The presence of plantations changes the thermal regime in the adjacent territories. In summer, the colder air of the green massif displaces the warmer and lighter air of the adjacent territory, lowering the air temperature in these areas. The degree of air temperature decrease depends on the plantation species (on the transparency of the crown, the reflectivity of the leaves, height and age), on the planting density and a number of other characteristics. Large-leaved trees are the best defenders against heat energy. So, for example, aspen passes through its foliage 10 times more energy than hawthorn. In the forest, air humidity increases, since the evaporating surface of the leaves of trees and shrubs, grass stems is 20 or more times larger than the soil area occupied by these plants. For a year, a hectare of forest evaporates into the air 1-3, 5 thousand tons of moisture, which is 20-70% of atmospheric precipitation. For example, an increase in forest cover by 10% can lead to an increase in the amount of annual precipitation by 10-15% [5]. In addition, about 90% of the incoming water evaporates from the surface of the leaves, and only 10% is used for plant nutrition. Air humidity in the middle zone in a forest or park in summer is 16-36% higher than in a city courtyard. Green spaces also contribute to an increase in air humidity in the adjacent open areas.

The forest takes an active part in gas exchange, primarily by absorbing carbon dioxide and releasing oxygen into the atmosphere. This natural phenomenon is called photosynthesis. So, a hectare of forest absorbs 8 kg of carbon dioxide (H2CO3) per hour, which are emitted by 200 people. The degree of absorption of carbon dioxide and the release of oxygen strongly depends on the type of plantation. Thus, the Berlin poplar is 7 times, the pedunculate oak is 4.5 times, the large-leaved linden is 2.5 times, and the Scots pine is 1.6 times more efficient in terms of gas exchange of Scotch spruce.

The forest also plays a significant role in cleaning the atmosphere from dust. Plants accumulate dust particles on the surfaces of leaves, branches and trunks. In this case, the effect of accumulation is largely determined not only by temperature, humidity and wind speed, but also by the plantation species. So, conifers 30 times, and birch 2, 5 times more dust retains than aspen. Dust content in urban and suburban parks is 1.5-4 times lower than in the industrial zone. Measurements have shown that the dustiness of the air under the trees is 20-40% lower than in the open adjacent areas. During the active period of the plant's life, one adult tree removes from the air: horse chestnut - 16 kg, Norway maple - 28 kg, Canadian poplar - 34 kg of dust.

The forest is also involved in cleaning the air from gaseous impurities. Colder air, creating vertical currents, and lower wind speeds in the area of green spaces, contribute to the movement of gaseous impurities into the upper atmosphere. This leads to a decrease in their number in the zone of green spaces by 15-60%. Different tree species have different resistance to atmospheric pollution while maintaining their ability to capture toxic impurities from the atmosphere. Thus, white acacia captures sulfur and phenol compounds from the atmosphere, without seriously damaging its foliage. From (c) the follow-up showed that sulfur dioxide severely damages vegetation.

Near chemical plants, the surface of the leaves of linden, birch and oak is burnt by 75-100%, and mountain ash - by 25-65%. Unresistant tree species to atmospheric pollution are: horse chestnut, Norway maple, spruce and common pine, mountain ash, lilac, yellow acacia, etc. The most resistant are: black poplar, white acacia, large-leaved poplar, Pennsylvanian maple, common ivy.

Plants secrete biologically active substances (phytoncides), which have high physiological activity in small quantities in relation to certain groups of living organisms. Biologically active substances kill pathogenic bacteria or retard the development of microorganisms. The effectiveness of biologically active substances of different plants is not the same. So, Atlas cedar causes the death of bacteria after 3 minutes of secretion, bird cherry - after 5 minutes, black currant - after 10 minutes, laurel - after 15 minutes.

The participation of forest areas is also great in reducing the noise level from transport highways and enterprises. The crowns of deciduous trees absorb 26% of the incident sound energy, and reflect and dissipate 74%. Two rows of linden trees are able to reduce the noise level by 2, 5-6 times, depending on the width of the planting strip without foliage and 7, 7-13 times, when the plants were with foliage. The degree of sound insulation depends on the species, height and planting pattern of trees and shrubs. Noise at the height of human growth on a street built up with tall buildings devoid of green spaces is 5 times higher than on the same street lined with trees due to the reflection of the noise of moving traffic from the walls of buildings.

Thus, the forest plays an important role on the planet in maintaining favorable conditions for the existence of all living organisms, including humans. The forest as a natural ecosystem participates in climate and sediment formation, maintains the gas composition of the atmosphere, provides home and food for many species and forms of plants and animals. However, today there is a serious problem of forest conservation.

The main part of forest ecosystems is in such countries as Russia (809 million hectares), Brazil (520 million hectares), Canada (310 million hectares), the USA (304 million hectares), China (207 million hectares), Democratic Republic of the Congo (154 million hectares) [8].

Moreover, the most valuable for maintaining the ecological balance on the planet are taiga and tropical forests. Tropical forests have a fairly high biological diversity, which contain up to 70-80% of all animals and plants known to science. According to the US Department of State, the annual loss of forests is equal to four areas of Switzerland (41,284 km²) [9].

In order to represent the scale of deforestation, this area can still be compared with the territory of the Moscow region (44,379 km²). The main reasons for forest decline are uncontrolled deforestation for agricultural land - 65-70% and logging - 19% (Fig. 7, 8, 9).

Most tropical countries have already lost more than half of their natural forests. For example, in the Philippines, about 80% of forests have been cleared, in Central America, forest area has decreased by 60%. In such tropical countries as Indonesia, Thailand, Malaysia, Bangladesh, China, Sri Lanka, Laos, Nigeria, Libya, Guinea, Ghana, the forest area has decreased by 50% [9].

Summing up, we can say that the preservation and increase in the area of forest ecosystems is the most important task of mankind, the fulfillment of which will ensure his survival in a favorable natural environment. Otherwise, humanity simply will not survive, since only the harmonious development of earthly civilization with nature gives a chance for life and development of humanity as a whole.

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