How do trees capture carbon dioxide


How Forests Store Carbon

Increases in carbon dioxide (CO2), and other pollutants in the atmosphere known to affect global climate, has caused some people to become interested in carbon capture and sequestration technology. This includes pumping CO2 underground into old coal mines and aquifers. While these technologies may work, they are still unproven and expensive at larger scales.

Fortunately, the best carbon capture technology has already exists: trees and forests. According to the US Forest Service, America's forests sequester 866 million tons of carbon a year, which is roughly 16% of the US annual emissions (depending on the year). Forests sequester or store carbon mainly in trees and soil. During the process of photosynthesis trees pull carbon out of the atmosphere to make sugar, but they also release carbon dioxide back into the atmosphere through decomposition. Carbon and other gases within forests are captured and released on a cycle. Forest management is able to influence these cycles and enhance carbon capture.

Trees

Trees are without a doubt the best carbon capture technology in the world. When they perform photosynthesis, they pull carbon dioxide out of the air, bind it up in sugar, and release oxygen. Trees use sugar to build wood, branches, and roots. Wood is an incredible carbon sink because it is made entirely of carbon, it lasts for years as a standing tree, and takes years to break down after the tree dies. While trees mainly store carbon, they do release some carbon, such as when their leaves decompose, or their roots burn sugar to capture nutrients and water.

Let's look at a real example, a white oak can live for 200 years; all that time it is pulling carbon out of the air and storing it. After several anthracnose outbreaks the tree dies, but it takes decades for the tree to rot. While it is slowly breaking down, the rotten tree is still keeping carbon out of the atmosphere.

Forests capture and store different amounts of carbon at different speeds depending on the average age of the trees in the stand and the number of trees in the stand. Young forests have many trees and are excellent at capturing carbon. Young trees grow quickly and are able pull in carbon rapidly. Not every small sapling becomes a large tree due to competition for light, resources, and growing space, but when they die and decompose little carbon is released. The trees that remain continue to grow and sequester more carbon as the forest matures.

Established or mature forests are made up of "middle-aged trees", which are medium to large, healthy, and have a large root system. Middle-aged trees grow slower than young trees, but the amount of carbon captured and stored is relatively greater. Some of large trees occasionally die, but they are quickly replaced by younger trees who take advantage of the new space. Since more trees are growing compared to those that are dying, the overall net productivity (how many trees grow versus how many die) is positive and carbon capture is enhanced.

Old-growth forests have a more fixed, or less dynamic, carbon cycle within live and dead trees and the soil. In old growth forests, large trees dominate by shading out small saplings, so recruitment of young trees and net productivity is zero. Still, the carbon is well contained within the big trees, slowly rotting logs, thick leaf litter and soil. Large individual trees may take up as much carbon as an individual middle-age tree, but since there are fewer trees in an old growth stand, the total additional carbon capture is often lower.

Soil

The carbon that is sequestered in forests comes in many forms. For example, forest soils contain plant roots, leaf litter, and other dissolved organic material. The amount of carbon stored in forest soils is variable, and how much carbon soil can sequester is dependent on many local factors like local geology, soil type, and vegetation. In some forests, like in Canada by the tundra, the soil holds more carbon than the trees, but in other forests, like the rain forest, the soil holds relatively little carbon and the trees store more carbon. This is because some soil types, like clay soils, can bind up a large amount of carbon, whereas sandy soils are not able to bind much carbon. Soils with more organic material (bits of wood, decaying leaves, or dead creatures) can store more carbon because organic material easily binds loose carbon molecules and the organic material itself is stored carbon. Soils that are frozen for a good part of the year or have a high-water table can also store large amounts of carbon because decomposition is slow.

Permanence

Besides capturing large amounts of carbon, forests are good at storing it for a long time. However, like all things natural, carbon in forests ultimately gets released into the atmosphere through decomposition, respiration, or other methods. Some places are better at storing carbon for long periods than others; this is called permanence. The carbon that makes up a center of a mature white oak remains bound up for a long time. It has been pulled out of the atmosphere a hundred or more years ago, and it will remain bound up until the tree dies and is decomposed. That process can take decades to centuries depending on how long the tree is alive. Carbon captured by a small trillium has little permanence. Trilliums are annual plants, so the aboveground plant dies annually and rapidly decomposes or they are commonly eaten by deer.

Examples

Let's look at how forest growth and soils affect the permanence of forest carbon. The Amazon rainforest appears to be a good place for carbon sequestration because it is full of big trees that grow rapidly. But research has found the Amazon is a poor carbon sink because there is little permanence. Whole trees rapidly decompose in the hot humid climate, the soils are not able to store a lot of carbon. The near constant rain also helps to break down organic material and wash away soil and nutrients. In contrast, the spruce forests of Alaska are excellent carbon sinks. The spruce grow large, decomposition is slow due to the cold, and the soil is able to lock up carbon in permafrost. Unfortunately, the growth rates in these forests is relatively slow due to the cold temperatures and limited growing season. Changes in global climate are also melting the permafrost, releasing much of the captured carbon. Pennsylvanian forests offer an ideal middle of the road solution. The trees grow well and are long-lived, decomposition occurs at a mild rate, and the soil stores a moderate amount of carbon. This means our forests have great potential to serve as an effective carbon sink and provide long-term carbon storage.

Management Strategies

While carbon capture in trees is a natural process, there are ways to encourage trees to sequester more carbon through forest management. The most important strategy is to keep forests as forests. When forests are converted to other types of land uses, carbon is released and the land loses its potential to store carbon. This does not mean that clear cutting (where silviculturally appropriate) must be stopped. Clear cutting resets the forests age and can in fact accelerate carbon capture by growing younger trees. Climate benefits also occur when timber products displace the use of other products that require the use of fossil fuels (e. g., plastics). When it comes to carbon, the best way to enhance carbon capture without cutting the existing forest is to increase forest cover. This can be done by planting old fields with a mix of native trees or restoring old mine sites.

Controlling invasive plant species is another important strategy for enhancing carbon capture. While many non-native/invasive plant species can grow rapidly and appear to be a good carbon sink, they are not. Invasive species disrupt native ecosystems, change the makeup of the local soil microbes, and prevent tree regeneration, all of which interferes with a forest's ability to sequestration carbon. Native trees and plants are adapted to thrive in local conditions and tend to function better as carbon capture mechanisms. Native plants also provide other important benefits such as wildlife habitat.

Practicing sustainable silviculture is essential for ensuring forests remain healthy and can also help enhance carbon capture. Harvesting is considered sustainable when decisions are based on silvicultural knowledge and follow a long-term management plan. Professional foresters are also important for helping owners meet multiple management objectives while maintaining the value of their stands. Forests that maintain their value are more likely to remain as forests in the future when ownership changes.

Uneven aged stands offer the best carbon capture services, as well as other benefits (e.g., wildlife habitat). In an uneven aged stand, there is continuous recruitment of younger trees, but older trees also remain and help hold carbon for long periods. Uneven aged stand management requires harvesting to occur through single tree or group selection. However, removing individual trees disturbs the soils in the local area. These soils also hold carbon and frequent disturbance over time can turn soils from a carbon sink to a carbon source. To help prevent soil disturbance in these stands it is important to extend the rotation period. For example, a hardwood forest that has been traditionally thinned every 10-15 years should be thinned ever 20-25 years, so the soils have time to recover between entries. In comparison, the rotation of even-aged forests do not need to be extended. In Pennsylvania, these harvests tend to occur every 80 to 100 years, which means the soils can remain undisturbed for long periods.

There are several other best practices you can adopt today for enhancing carbon storage in trees and soils. When harvesting, it is important to reduce damage to the soil. This can be done by putting slash on skid trails, not harvesting in the rain, harvesting in the winter, and using forwarders instead of whole-tree skidding. Harvesting trees that are slowly growing can also contribute to carbon sequestration. Instead of letting mature trees die and decompose, they can be removed and cut into products like 2x4s, flooring, or cabinets which go into homes and buildings and that could be around for centuries. The Liberty Bell is a great example of how high-quality wood products can help store carbon. The wooden yoke of the Liberty Bell is made from American elm harvested in the 1770s (there is some disagree on how old the beam is). Instead of decomposing in a forest centuries ago, the carbon in that wood is still around today holding up the Bell. 

Closing Remarks

Forests are an important carbon sink, as both trees and forest soil are able store large amount of carbon for a long time. However, carbon management is not just about deciding which trees to cut, but also where harvesting and planting occurs on the landscape. It is important to maintain a mix of tree ages and forest types with a focus on young and established forests, as these forests capture and sequester the most carbon. However, this does not mean old-growth forest should be sacrificed to create more young forests. This could release large amounts of carbon, and a new forest would take decades to sequester as much carbon as currently stored in the old-growth forest. The key is to use planning and management strategies that help capture additional carbon while minimizing losses of stored carbon. Professional foresters can help you understand the potential of your land and forests for enhancing carbon capture through forest management, while maintaining the value and health of your forests.

Technical Note - How do Trees Store Carbon? - Creating Tomorrow's Forests

Human activity such as burning fossil fuels and deforestation is creating a surplus of carbon dioxide and other greenhouse gases in the atmosphere, which is causing an increase in global temperatures. If the rate at which we emit carbon does not dramatically slow down, this increase could have dramatic effects on our weather systems, increase sea levels, displace millions of people and cause many other species to become extinct. Planting billions of trees has been suggested as one of the quickest and most cost-effective ways of fighting the climate emergency, as trees absorb and store (sequester) carbon. By understanding how trees store carbon, we can look at forests as a method of sequestering some of the excess carbon produced by anthropogenic activities and assess how effective this mitigation might be.

Trees store carbon predominantly in the form of carbohydrates, for immediate and long-term growth. Carbohydrates are produced using photosynthesis, the process that occurs within all plants to convert sunlight into chemical energy.

Photosynthesis is the basis of almost all life on Earth as it converts inorganic compounds into fuel for living organisms. As well as providing energy for plants to live and grow, it provides oxygen for other organisms to breathe and stored carbohydrates that animals can consume. Trees absorb light into their leaves into green-pigmented chloroplasts in cells, draw up water through their root system and take in carbon dioxide via stomata, tiny holes in their leaves. The light energy is used to power the chemical reaction within the chloroplasts, which splits the water and carbon dioxide and recombines them into glucose, an organic compound that includes carbon.

‍The glucose is then carried around the tree for immediate energy via the phloem, a layer just under the bark and the oxygen is emitted via the stomata on the leaves. Once the glucose reaches a cell where it is needed, it is broken back down via respiration into energy for the cell, carbon dioxide and water. The carbon dioxide and water are carried back to the leaves and emitted via the stomata. This is how the tree keeps functioning overnight when there is no sunlight, as cellular respiration continues. Any unused glucose is stored as starch in the trunk, branches and roots for later use. Although trees do produce carbon dioxide during respiration, they are net absorbers of CO2 because of this carbon store.

Following photosynthesis, glucose (and the constituent carbon) that is not used is stored in the form of starch in the sapwood layer, or xylem, of a tree trunk.

The starch is stored in a network of interlinked cells called the symplast until it is needed. During dormant periods when they do not have any leaves for photosynthesis, deciduous trees respond to triggers such as lowering temperatures by converting the starch back to sugars including glucose by a process called hydrolysis. The sugars are then transported to where they are needed from the symplast, although the exact mechanism is unclear. The process of respiration then breaks the glucose back down into energy, carbon dioxide and water. Trees need to mobilise these stored resources overwinter for maintenance but particularly at budburst, to create new leaves, when there are no existing leaves for photosynthesis. The carbon store in the sapwood is transitory, therefore, available to be used for respiration when the tree needs it.

The heartwood of a tree is formed from the xylem as the tree grows and it provides structural strength and defence against disease and decay. It is considered to be biologically inactive and it no longer transports or stores carbohydrates. Heartwood does store carbon in the form of lignin (a structural component), resins and phenols and indeed in many tree species there is a higher concentration of carbon in the heartwood than the sapwood. This carbon store in heartwood can be significant, especially in long-lived species such as California redwoods (Sequoia sempervirens), where 63-77% of aboveground carbon is stored in the heartwood. The lack of transition of the carbon from the heartwood to the rest of the tree means that this carbon is stored permanently until the tree dies or is cut down. If a tree is cut down for timber, the carbon remains stored in the wood, so it can be used in construction or for making furniture or paper – it is only when wood or paper is burned or rots that the carbon is released. Recent research has indicated that there is huge potential for long-term carbon storage in timber if we change construction methods, which would have the additional benefit of reducing the high emissions from using concrete in construction (8% of global carbon emissions are due to cement). There is high variation in how much heartwood different tree species have and indeed some fast-growing species such as silver birch (Betula pendula) do not have heartwood at all.

Carbon in the form of starch is not only stored in the trunk, but also in the root system of trees. The proportion of a carbon stored by a tree in the belowground root system is estimated to be around 24%, although root biomass varies significantly between species. Starch reserves can move between the trunk and the root system in response to changing temperatures. Indeed when the soil is warmer than the air in autumn and winter starch accumulates in the roots, whereas there is a shift of carbohydrates to the above ground biomass when the air is warmer than the soil in spring and summer.

Understanding the carbon storage dynamics of how the tree species in a forest are storing carbon can help us to understand how best to structure new forests or reforestation projects for maximum carbon capture.

By storing carbon temporarily and permanently in their biomass, trees act as a sink for carbon, sequestering more than they return into the atmosphere. Carbon is stored not only in the biomass of the trees themselves but around 48% of carbon is stored in the leaf litter and soil of the forest, meaning that a healthy forest ecosystem stores far more carbon than trees individually. This all contributes to making forests the largest component of the 29% of atmospheric carbon that is absorbed by land. A pivotal study calculated that forests have the potential to absorb up to 25% of the current atmospheric carbon pool and are one of the most cost-effective tools to reduce the CO2 surplus. To date, forests appear to be sequestering half of the excess atmospheric carbon dioxide being produced by anthropogenic activity, and their productivity has increased as a result of higher levels of CO2.

There is a wealth of research ongoing into how to plant and manage forests to maximise their carbon sequestration potential, because this can have a dramatic impact on how effective a forest is at absorbing and storing carbon. Watching the NASA simulation of how deciduous forests absorb carbon when they come into leaf in May / June gives a striking insight into how effective this process is.

Given what we understand about how trees store carbon, it is evident that preserving existing forest with long-lived trees is critical to reducing global warming. Although harvested timber stores carbon, the dynamic carbon storage of the tree through photosynthesis and respiration is lost when it is cut down. There has been much discussion of whether tree growth and respiration slows down as trees age, but more recent studies have found that older trees do not slow down photosynthesis and hence carbon absorption. By contrast, new forests and forest regrowth absorb carbon more quickly than old forests due to competition between saplings. By appreciating these dynamics and factoring in our understanding of how different tree species store and use carbohydrates, it becomes clear that planting mixed species forests can greatly increase carbon storage. This is reinforced by research showing that natural forests are 40 times better at sequestering carbon than plantations, partly due to the soil, leaf litter and deadwood present in natural forests.

Most of the current tree planting projects have focused on the tropics, where trees grow quicker in the warm temperatures and high humidity, but many have planted non-native fast-growing species, which does not enhance biodiversity or restore local forest. Although traditionally tropical forests have been considered to be the most important store of sequestered carbon, temperate zones may be capable of storing more carbon per hectare, with boreal conifers in particular storing more carbon in their wood. Mangrove forests sequester the most carbon per hectare of any forest type, but they are disappearing rapidly due to land clearance for agriculture and shrimp farming. With evidence that tropical forest carbon sequestration is slowing down as a result of deforestation, we urgently need to protect existing forests. If we combine this with finding more sustainable ways of harvesting forest products such as timber, and planting native, new forests, we can ensure that trees really do help us in the fight against climate change.

Scientists have developed mechanical trees that absorb carbon dioxide

The construction of artificial forests can stop the climate catastrophe.

Researchers at the University of Arizona have developed mechanical trees that capture carbon dioxide, according to the Daily Mail.

Forests of mechanical trees with layers of discs designed to absorb carbon dioxide can prevent climate change. Developed by Professor Klaus Lackner, mechanical trees are thousands of times more efficient than their natural counterparts.

Photo: Arizona State University

The "trees" are tall vertical columns of disks about 1.5 meters in diameter each. The poles are set at a distance of 5 cm from each other. The columns are covered with chemical resin and look like a stack of vinyl records.

Resin captures carbon dioxide from the air as it hits the surface. Once filled, the discs fall into a barrel where the CO 2 evaporates and is placed in a closed environment. Carbon dioxide in mechanical trees will simply be stored, unlike real trees, which convert the gas back into oxygen. Other projects have already explored the reuse of carbon dioxide stored in such tanks, for example, to produce synthetic fuel that can be used in aircraft.

It is planned to create three large mechanical farms for "growing" trees. The first is due to open in Arizona at the end of 2022 with the support of a $2.5 million grant from the US Department of Energy. Once all three farms are operational, they will be able to absorb 1,000 tons of CO 2 per day, which will be an important step in changing global carbon balance.

Can we now imagine what the climate on Earth will be like in 1000 years?

They invented turning carbon dioxide into stone

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Give an idea of ​​the seasons

Trees are an integral part of nature and the main component of many ecosystems on the planet. Their main function is to purify the air. It is easy to verify this: go into the forest and you will feel how much easier it is for you to breathe among the trees than on the city streets, in the desert or even in. The thing is that tree forests are the lungs of our planet.

The process of photosynthesis

Purification of the air occurs during the process of photosynthesis, which is carried out in the leaves of trees. In them, under the influence of solar ultraviolet and heat, carbon dioxide exhaled by people is processed into organic elements and oxygen, which then take part in the growth of various plant organs. Just think, trees from one hectare of forest in 60 minutes absorb carbon dioxide produced by 200 people in the same period of time.

By purifying the air, trees remove sulfur and nitrogen dioxide, as well as carbon oxides, dust microparticles and other elements. The process of absorption and processing of harmful substances occurs with the help of stomata. These are small pores that play a crucial role in gas exchange and water evaporation. When micro-dust particles fall on the surface of the leaves, they are absorbed by plants, making the air cleaner. However, not all breeds filter the air well, ridding it of dust. For example, ash, spruce and linden trees are difficult to tolerate a polluted environment. Maples, poplars and oaks, on the contrary, are more resistant to atmospheric pollution.

Influence of temperature on air purification

In summer, green spaces provide shade and cool the air, so on a hot day it is always nice to hide in the shade of trees. In addition, pleasant sensations arise from the following processes:

  • evaporation of water through the leaves;
  • deceleration of wind speed;
  • additional air humidification due to fallen leaves.

All this affects the decrease in temperature in the shade of trees. Usually it is a couple of degrees lower than on the sunny side at the same time. With regard to air quality, the temperature regime affects the spread of pollution. Thus, the more trees, the cooler the atmosphere becomes, and the less harmful substances evaporate and are released into the air. Also, woody plants emit useful substances - phytoncides that can destroy harmful fungi and microbes.

People make the wrong choice by destroying entire forests. Without trees on the planet, not only thousands of species of fauna will die out, but also people themselves, because they will suffocate from dirty air, which there will be no one else to clean. Therefore, we must protect nature, not destroy trees, but plant new ones in order to somehow reduce the damage caused by mankind to the environment.

Trees have been known to us since school days as an indispensable filter of natural origin. Its leaves contain chlorophyll, which absorbs carbon dioxide and then supplies our planet with oxygen.

  • In summer, 1 tree is able to convert their bad air into good air with a volume that is enough for 4 people to breathe.
  • Green spaces of 1 hectare are capable of absorbing about 8 liters of carbon dioxide in 1 hour, and then converting it into oxygen, which is enough for 30 people.
  • Trees also benefit the earth, providing its air exchange and cleaning the soil layer of 45 meters.

Some tree species are used specifically for urban greening. Often on the streets you can find chestnut and poplar. The chestnut tree is able to recycle about 20 thousand m3 of polluted air, when a 25-year-old poplar outperforms spruce by 7 times in its purification capabilities, and 10 times by moistening.

The foliage of trees has the properties of dust absorption, neutralization and reduction of the degree of harmful substances in the air. Leaves of lilac, elm, acacia are noted for good data. It only takes 400 units of young poplar plants to eliminate 340 kg of city dust, when the same amount of elm can handle 1900 kg!

Air temperature reduction

The hot summer season is characterized by constant air streams that come from hot asphalt, roofs of buildings and houses, cars, etc. These streams carry a lot of dirt, dust, carcinogens. It’s good if there are trees nearby, the temperature of the leaves of which pushes hot air from the coatings and deposits dust. We all always hide in the shade of trees, where the air is not so dry and “heavy”.

Metals in the air

The comfort of having a car has deprived us of natural and clean air, especially in metropolitan areas. A whole kilogram of metal is capable of throwing a car into the atmosphere during the year of its operation!

It is harmful to the breath, as well as to plants grown near the highway and often the vegetables we eat. This also includes animals that feed on grass near the road, and then give milk, meat, etc.


Lead (read more about) in the atmosphere, when it is overabundant, causes leaf fall in trees, and in a non-autumn period. For trees, this metal is very harmful, unlike mosses, larches. By concentrating lead in their leaves, trees have the ability to recycle carbon dioxide.

During the growing season, a tree can accumulate the amount of lead that can be obtained from 130 liters of gasoline. From this we can draw a simple conclusion that in order to neutralize the harm from cars, 10 trees per 1 unit are needed.

Bacteria hunting

Trees are multifunctional plants of our planet, because they not only supply the world with oxygen and consume harmful substances, save us from the sun, heavy metals, but are also able to neutralize harmful microbes.

Phytoncides - components of green spaces that hunt for harmful bacteria, and are most concentrated in: white acacia, willow, birch, spruce, pine, poplar, bird cherry, etc. It is important that these substances kill both human pathogens and and animals. It is especially harmless in coniferous forests, because there are 2 times less bacteria than in deciduous forests.

Not in vain, even at school we are taught to appreciate and preserve green spaces, because their work is so important for our healthy life, the beauty of the world around us. Moreover, the present catastrophically lacks such a natural filter as trees.

If you are interested, see which indoor plants purify the air in the house

The role of green spaces in cleaning the air of cities is great. Plants take in carbon dioxide and release oxygen. A medium-sized tree in 24 hours restores as much oxygen as is necessary for the breathing of three people. In one warm sunny day, a hectare of forest absorbs 220-280 kg of carbon dioxide from the air and releases 180-220 kg of oxygen. 1 hectare of urban green spaces is released per day up to 200 kg of oxygen.

The results of studying the dust- and gas-holding role of tree and shrub plantings indicate that the dust content of the air among green spaces is 2-3 times lower than in open areas. Species of trees and shrubs with rough, hairy leaves (elm, linden, maple, lilac) have the highest dust-holding capacity.

The gas-protective role of green spaces is due to the ability of plants to capture gases contained in the atmospheric air and resistance to them. Poplar, Canadian maple, honeysuckle can be attributed to the most gas-resistant.

The influence of trees and shrubs on the reduction of airborne concentrations of harmful gases occurs mainly through the dispersion of these gases into the upper atmosphere by tree crowns, and to some extent through the absorption of gases by leaves through stomata and leaf cell membranes. It is known, for example, that green spaces capture sulfur dioxide from the atmospheric air and accumulate it in the form of sulfates in their tissues.

The ability of plants to absorb carbon dioxide and release oxygen is of great importance in improving the health of the air in populated areas. On average, 1 hectare of green spaces absorbs 8 liters of carbon dioxide per hour. The intensity of this process depends on the characteristics of photosynthesis of various species of trees and shrubs.

A medium-sized tree in 24 hours restores as much oxygen as is necessary for the breathing of three people. In one warm sunny day, a hectare of forest absorbs 220-280 kg of carbon dioxide from the air and releases 180-200 kg of oxygen. Poplar has the highest oxygen productivity.

Oxygen enters per 1 ton of birch wood growth: in the composition of CO2 1335 kg, in the composition of H2O 488 kg, in total 1823 kg. But the wood itself contains 430 kg of oxygen, and the remaining 1393 kg are released into the atmosphere.

It has been established that 1 ha of a 20-year-old pine plantation, giving an average annual growth of 5 m3 per 1 ha, absorbs 9.35 tons of CO2 every year and emits 7.25 tons of O2. The most obvious in this respect are middle-aged plantations. So, 1 hectare of a 60-year-old pine forest gives an annual increase of an average of 7.51 m3 per 1 ha, absorbing 14. 44 tons of CO2 during this time and releasing 10.92 g of O2. Photosynthesis proceeds even more actively in 40-year-old oak plantations, where the absorption of CO2 per year per 1 ha is 18 g, and the release is -13.98 t.

One hectare of urban plantings absorbs 8 kg of carbon dioxide in 1 hour, which is exhaled by 200 people during the same time. In the conditions of the city, green spaces are a factory of clean air, unsurpassed cleaners and orderlies of the atmosphere. Green spaces absorb not only carbon dioxide from the air, but also purify the atmosphere of carbon monoxide, reduce its concentration to natural - about 0.00001%.

Some plants can absorb the most harmful gases. It has been established that forest communities daily process up to 500 thousand cubic meters of air per 1 ha of forest with an assimilation apparatus. The total air purification capacity of full-fledged forest stands, which form 4 tons of leaves per 1 ha, is about 10 tons of toxic gases during the growing season. Only one tree during the growing season is able to absorb up to 12 kg of sulfur dioxide.

Students of the Kazakh University, together with scientists from the Botanical Garden of the Republican Academy of Sciences, studied the process of adaptation in the city of more than three hundred plant species. Studies have shown that the development of green spaces slows down in an industrial city, but some individuals are rapidly growing. These are juniper, barberry, hawthorn. The rose also belongs to the nursery plants.

The effect of woody vegetation on the content of harmful chemical compounds in the urban air is also manifested in the ability of trees to oxidize the vapors of gasoline, kerosene, diesel fuel, acetone, etc. in the urban air. Many plants can absorb aromatic hydrocarbons, carbonyl compounds, esters and essential oils from the atmosphere. There is information about the absorption of phenols by plants. A large phenol-accumulating ability is possessed by: common lilac, privet, white mulberry. In addition, green spaces are capable of capturing radioactive substances contained in the air.

Table 1

The best green filters for biological purification of atmospheric air in cities

Studies have shown that poplar is the best "orderly" in the zone of strong constant gas contamination. For comparison, over 5 summer months, a 25-year-old oak absorbs 28 kg of carbon dioxide, linden - 16, pine -10, spruce - 6, and an adult poplar - as much as 44 kg. Small-leaved linden, ash, lilac and honeysuckle also have good absorption qualities. In the zone of weak periodic gas pollution, more sulfur is absorbed by the leaves of poplar, ash, lilac, honeysuckle, linden, less - elm, bird cherry, maple.

During the growing season, growing black poplar deposits 44 kilograms of dust, white poplar - 53 kilograms; white willow and ash-leaved maple, respectively, 34, 30 kilograms. One hectare of spruce forest precipitates 32 tons of dust per year, oak - 54, beech - 68 tons. This function is best performed by trees and shrubs with pubescent, viscous, sticky, rough leaves. Elm, for example, retains 6 times more dust than poplar.

The influence of green plantings on air dustiness and decrease in gas concentration depends on the nature of plantings: their density, configuration, structure.

Everyone knows that trees purify the air . Being in a forest or a park, you can feel that the air is completely different, not the same as on dusty city streets. It is much easier to breathe in the shady coolness of the trees. Why is this happening?

The leaves of trees are small laboratories in which, under the influence of sunlight and heat, the carbon dioxide contained in the air is converted into organic substances and oxygen.
Organic matter is processed into the material from which the plant is built, i.e. trunk, roots, etc. Oxygen is released from the leaves into the air. In one hour, one hectare of forest absorbs all the carbon dioxide that two hundred people can produce during this time!

Trees clean the air by absorbing pollutants

The leaf surface is capable of trapping airborne particles and removing them from the air (at least temporarily). Airborne microscopic particles can enter the lungs, which can lead to serious health problems or tissue irritation. So it is very important to reduce their concentration in the air, which trees successfully do. Trees can remove both gaseous pollutants (sulfur dioxide, nitrogen dioxide and carbon monoxide) and particulate matter. Purification mainly occurs with the help of stomata. Stomata are small windows or pores on the leaf through which water evaporates and gas exchanges with the environment. Thus, dust particles, before reaching the ground, settle on the leaves of trees, and under their canopy the air is much cleaner than above the crowns. But not all trees can tolerate dusty and gassy conditions: ash, linden and spruce suffer greatly from them. Dust and gases can lead to blockage of stomata. However, oak, poplar or maple are more resistant to the harmful effects of a polluted atmosphere.

Trees cool the temperature during the hot season

When you walk under the scorching sun, you always want to find a shady tree. And how nice it is to take a walk in a cool forest on a hot day! Being under the crown of trees is more comfortable not only because of the shade. Thanks to transpiration (that is, the process of evaporation of water by a plant, which occurs mainly through the leaves), lower wind speed and relative humidity, a certain microclimate is created for the fallen leaves under the trees. Trees suck up a lot of water from the soil, which then evaporates through the leaves. All these factors together affect the air temperature under the trees, where it is usually 2 degrees cooler than in the sun.

But how does lower temperatures affect air quality? Many pollutants begin to be released more actively with increasing temperature. A perfect example of this is a car left in the sun in the summer. Hot seats and door handles create a suffocating atmosphere in the car, so you want to turn on the air conditioner faster. Especially in new cars, where the smell has not yet disappeared, it becomes especially strong. In particularly sensitive people, it can even lead to asthma.

Trees emit volatile organic compounds

Most trees emit volatile organic substances - phytoncides. Sometimes these substances form haze. Phytoncides are able to destroy pathogenic microbes, many pathogenic fungi, have a strong effect on multicellular organisms and even kill insects. The best producer of therapeutic volatile organic substances is the pine forest. In pine and cedar forests, the air is practically sterile. Pine phytoncides increase the general tone of a person, have a beneficial effect on the central and sympathetic nervous system. Trees such as cypress, maple, viburnum, magnolia, jasmine, white locust, birch, alder, poplar and willow also have pronounced bactericidal properties.

Trees are vital to keeping the air and the entire ecosystem clean on Earth. Everyone understands this, even small children. However, deforestation is not slowing down. World forests have decreased by 1.5 million square meters.


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