Main functions of forests

Green plants are consumers of carbon dioxide and producers of oxygen. Usually, one hectare of broad-leaved forest can consume 1000 kg of carbon dioxide and release 730 kg of oxygen in one day.

Purify the air:

Experiments show that trees absorb all kinds of toxic gases in the low concentration range, thus purifying the polluted environment.

For example, a hectare of Cryptomeria fortunei forest can absorb 60 kilograms of sulfur dioxide every month. Canna, rose, clove, chrysanthemum, ginkgo and acacia can also absorb sulfur dioxide.

Filter dust:

The ability of forest to absorb dust is 75 times that of bare land. One hectare of beech forest absorbs 68 tons of dust a year.

In addition, forests play a very important role in water conservation, soil and water conservation, wind and sand fixation, and climate regulation.

Experience at home and abroad proves that if the forest coverage rate of a larger country or region is above 30% and the distribution is relatively uniform, then the ecological environment of this country or region will be superior and the production of agriculture and animal husbandry will be relatively stable.

Kill bacteria:

According to the survey, the number of bacteria in the air in downtown areas is more than 7 times that in green areas. One of the reasons is that some plants can secrete powerful antibiotics, such as oranges, lemons, Sabina vulgaris, black walnuts, French phoenix trees and other plants, which have strong bactericidal power.

Eliminate noise:

Pieces of trees can absorb and block sound, so planting trees in cities can effectively reduce noise.

The role of forests

From a scientific point of view, forests refer to those areas of the earth covered with trees. These areas provided food, fuel, wood, medicinal materials and other means of subsistence for early human life. The origin of human civilization is inseparable from forests. At that time, the raw materials of human tools, houses, cities, wheels and wooden boats all came from forests. The forest has also sprouted the beauty of human beings and made countless artistic creations. The impact of forests on human survival, unlike food and water, will soon be fatal if it is lacking. However, as a "regulator", forest affects the living environment of human beings in many ways and restricts human security.

1. Forests are air purification. With the rapid development of industrial and mining enterprises and the sharp increase of fossil fuels for human life, a certain amount of harmful gases are mixed in the polluted air, which threatens human beings. Among them, sulfur dioxide is a widely distributed and harmful gas. All living things have the ability to absorb sulfur dioxide, but the speed and ability of absorption are different. Plants have a huge leaf area, and their absorption of sulfur dioxide is far greater than that of other species. According to the measurement, sulfur dioxide in the air planted in forest is less than that in open space 15-50%. If it is in high temperature and high humidity summer, with the vigorous physiological activity function of trees, the speed of forest absorbing sulfur dioxide will accelerate. When the relative humidity is above 85%, the speed of sulfur dioxide absorption by forests is 5- 10 times of the relative humidity 15%.

2. Forests have natural epidemic prevention functions. Trees can secrete fungicides with strong lethality, kill germs and microorganisms in the air, and have a certain health care effect on human body. Some people have measured the content of bacteria in cubic meters of air in different environments: parks with large human flow 1000, downtown streets 30000-40000, and forest areas only 55. In addition, the amount of fungicides secreted by trees is also considerable.

3. Forest is a natural oxygen factory. Oxygen is the basic condition for human life. The human body must always breathe oxygen and expel carbon dioxide. A healthy person will not die if he doesn't eat or drink for three or two days, and will die if he lacks oxygen for a few minutes. This is common sense. According to the literature, a person needs to inhale 0.8 kg of oxygen and expel 0.9 kg of carbon dioxide every day to survive. Forests need to grow. Leaves produce one gram of glucose through photosynthesis, which can consume all the carbon dioxide contained in 2500 liters of air. According to theoretical calculation, every cubic meter of wood grown in the forest can absorb about 850 kilograms of carbon dioxide in the atmosphere. If trees grow in the peak season, one hectare of broad-leaved forest can absorb one ton of carbon dioxide every day and produce 750 kilograms of oxygen. 10 square meter of forest or 25 square meters of grassland can absorb all the carbon dioxide breathed by a person and supply the required oxygen. It is true that trees also have the characteristics of absorbing oxygen and expelling carbon dioxide at night, but because the amount of carbon dioxide inhaled during the day is very large, almost 20 times that at night, the side effects at night are very small. On a global scale, forest green space handles nearly 1000 billion tons of carbon dioxide for human beings every year and provides 60% clean oxygen for the air. It can reduce greenhouse gases and thermal effects.

4. The forest is a natural silencer. With the development of transportation, especially in cities and towns, noise is more and more harmful to human beings. According to the research results, the noise is below 50 decibels and has no effect on people. When the noise reaches 70 decibels, it will cause obvious harm to people; If the noise exceeds 90 decibels, people can't work long hours. As a natural muffler, forest has a good anti-noise effect. Experiments show that parks or woodlands can reduce noise by 5-40 decibels, which is 5-25 decibels more than the natural attenuation effect in the open space with the same distance from the sound source. The car tweeter can reduce the noise 10-20 decibels when it passes through the multi-level forest belt composed of 40 meters wide lawns, shrubs and trees, which is 4-8 decibels more than the natural attenuation effect in the open area. Planting trees in urban streets can also reduce noise by 7-65,438+00 decibels. To achieve good noise reduction effect, it must be at least 6 meters (forest canopy) wide in the city.

5. Forests can regulate climate. The dense forest canopy can absorb, scatter and reflect some solar radiation energy in summer, thus reducing the increase of ground temperature. Although most of the leaves in the forest wither in winter, the dense branches can still reduce the wind speed blowing across the ground, thus reducing the air flow and playing the role of heat preservation and moisture preservation. According to the measurement, the temperature in summer forest is 2-4℃ lower than that in urban open space, and the relative humidity is 15-25. Compared with asphalt concrete cement pavement, the air temperature is lower 10-20℃. Because the roots of trees go deep into the ground, they constantly absorb the water in the deep soil for transpiration, which makes the forest form fog normally and increases precipitation. Through analysis and comparison, the annual precipitation in forest areas is higher than that in non-forest areas 10-30%. According to foreign reports, in order to protect the natural environment, the green coverage rate of forests should account for 20% of the total area.

6. Forests can change the low-level airflow, prevent sandstorms, relieve floods, conserve water and soil. Due to the blocking and friction consumption of forest trunks, branches and leaves, the wind speed entering the forest area will be obviously weakened. According to the data, dense forest canopy can reduce the wind speed in summer by up to 50%. The wind speed changed little 200 meters before entering the forest. It takes about 500- 1000 meters to recover the speed before crossing the forest. Humans use this function of forests to plant trees and control desertification.

The rotten layer of forest surface litter is increasing, forming a thick humus layer, just like a huge sponge that absorbs rainwater, which has powerful functions of absorbing water, delaying runoff and weakening flood peak. In addition, the canopy can also intercept rainwater, reduce the impact of rainwater on the ground, and maintain soil and water. According to calculation, the canopy can block 10-20% of the precipitation, and most of it evaporates into the atmosphere. The rest falls to the ground or seeps into the soil along the trunk to become groundwater, so a forest is a reservoir. The roots of forest vegetation can firmly fix the soil, protect the land from rain erosion, prevent soil erosion and prevent land desertification.

7. Forests can remove dust and filter sewage. The smoke and waste gas emitted by industrial development seriously pollutes the air and threatens human health. The folds and fluff on the leaves of tall trees and the viscous oil and juice secreted by stomata can stick a lot of dust and have obvious blocking, filtering and adsorption effects. According to the data, spruce can absorb 8. 14 grams of dust per square meter every day. Elm forest is 3.39g, generally speaking, the air dust concentration in forest area is lower than that in non-forest area 10-25%. In addition, the forest has a strong ability to purify sewage. According to foreign research, the bacterial content in sewage can be reduced by half when it passes through the forest land of about 40 meters, and then the bacterial content in sewage can be reduced to more than 90% at most with the increase of the distance through the forest land.

8. Forest is the habitat of many kinds of animals, the growth place of many kinds of plants, and the most active area of biological reproduction on the earth. Therefore, forests protect biodiversity resources; Moreover, whether around the city or in the outer suburbs, forests are extremely valuable natural landscape resources.

Due to the large consumption of forest wood resources, the forest area on the earth is getting smaller year by year, which has caused many environmental problems, such as drought and lack of rain, climate warming, reduction of animal and plant resources, soil erosion, sandstorm, air pollution and so on. Therefore, the value of forest to environment and ecology is much higher than the value of wood it provides.

Therefore, planting trees, expanding forest area and increasing forest resources are of great significance to economic, social, environmental and human survival.

The role of forests

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Forests not only have great economic benefits, but also have great ecological and social benefits.

Forest is a treasure house of human resources. In addition to providing a lot of wood, forests can also produce products with great economic value, such as rosin, tannin extract, lac, camphor, tung oil, rubber and so on. There are extremely rich species resources in the forest, and the species in the tropical rain forest alone account for 50% of all species on the earth. In the forests of China, there are a large number of edible plants, such as dates, chestnuts, persimmons and kiwis. There are also rich medicinal resources. In recent years, anticancer drugs such as harringtonine, maytansinone and camptothecin have been found in forest plants in China. There are also a large number of exotic flowers and plants and exotic animals in the forest, and the list is endless.

Forest is the green umbrella of soil. Dense branches and leaves can intercept rainfall and weaken the erosion of soil by water flow. Herbs and litter under the forest cover the soil surface like a soft sponge, which can not only absorb water, but also fix the soil; Huge roots crisscross and have strong adhesion to soil. In addition, forests can resist the erosion of soil by storms. Relevant observation results in China show that the soil erosion of forest land is much smaller than that of barren slope land.

The forest is a huge oxygen factory. All living things (including people) cannot do without oxygen. Biological breathing constantly consumes oxygen in the atmosphere and releases carbon dioxide. Plants absorb carbon dioxide in the atmosphere through photosynthesis and release a lot of oxygen, thus maintaining the balance of oxygen and carbon dioxide in the atmosphere. People will not be threatened by lack of oxygen. The ability of forests to produce oxygen is several times to dozens of times higher than that of plants in grasslands and farmland. 1 hectare of broad-leaved forest can absorb carbon dioxide 1000 kg per day and release 730 kg of oxygen, which can be used by nearly 1000 people 1 day.

The forest is a huge reservoir. Rainfall falls into the litter under trees and loose and porous woodland soil, which will accumulate, just like reservoir water storage. After the rain clears, a large amount of water evaporates into the atmosphere through transpiration of trees, which makes the air in forest areas moist and increases precipitation. Forests play a very important role in mitigating drought and flood disasters.

The forest is a good vacuum cleaner. When the airflow carrying all kinds of dust meets the forest, the wind speed will decrease, some dust particles will fall to the ground, and the other part will be stuck by the fluff, mucus and grease on the leaves. Each hectare of forest can absorb an average of 50-80 tons of dust every year. The dust content in the air of urban green space is less than half that of non-green space.

The forest is the health care doctor of nature. Every leaf is a poison filter. In photosynthesis, the stomata on the leaf surface are opened, and toxic substances in the air enter the leaf tissue with the air and are stored in plants. The gas released by photosynthesis is pure and nontoxic. According to statistics, Cryptomeria fortunei forest can absorb 720 kg m sulfur oxides every year. L kg of cypress leaves can absorb 1.57 g of hydrogen fluoride within 95 hours. Forests can also kill bacteria. Many trees can secrete fungicides and directly kill bacteria in the air. For example, 1 ha cypress forest can secrete 50 kilograms of phytoncide day and night, which can kill diphtheria, tuberculosis and other germs. In cities, the content of bacteria in the air in downtown areas is higher than that in green areas (such as parks).

The forest is a green sound barrier. Noise is a kind of physical contamination, which seriously harms people's physical and mental health. Dense crown and rough trunk have a strong absorption and reduction effect on noise. Sound waves will be strongly reflected when they meet the hard and flat building surface, but once they meet the forest, they will fall on the soft beach like a ball and will not bounce back. The green belt on the main road has obvious effect on reducing automobile noise. The forest bandwidth is 20 ~ 30. The forest belt with a width of 40 meters can reduce the noise10 ~15db.

In a word, forest is not only a green treasure house, but also a green barrier for human living environment. So, how should we treat it?

Forest ecosystem is the foundation of sustained and healthy economic development.

Economy and ecology complement each other. Economic activities are taken from nature and returned to nature. The process of economic development can not be separated from the foundation of ecosystem for a moment. From a global perspective, the direct and partial indirect economic losses caused by ecological damage in 1996 have accounted for 14% of the world GNP. From China's point of view, the direct economic loss caused by various natural disasters is as high as 200 billion yuan every year, and the grain production reduction caused by floods exceeds 654.38+0 billion kilograms. It can be seen that to achieve sustainable economic development, we must protect and build a good ecosystem.

Forest ecosystem is a buffer to control global warming.

Due to the recent extensive use of fossil fuels and the large-scale reduction of forests, the concentration of atmospheric carbon dioxide has increased rapidly, resulting in the "greenhouse effect" and global warming trend. The results show that the reduction of forest area accounts for about 30 %-50% of the total effect of all factors in increasing atmospheric carbon dioxide concentration. The consequences of the greenhouse effect are amazing. First, it will lead to changes in rainfall patterns. Second, it will lead to sea level rise. Third, it will lead to the death of many plant communities growing on land due to temperature changes. Such changes will further promote the temperature rise and form a vicious circle of the global ecosystem.

Forest ecosystem is the foundation of flood control and soil and water conservation.

The loss caused by river flooding is no less than that caused by war. 198 The floods in the Yangtze River, Songhua River and Nenjiang River basins in China caused direct economic losses of 255.09 billion yuan. If the cost of post-disaster reconstruction is added, the amount of economic "compensation" will be even more amazing. There are countless examples of this. We can't always attach importance to economic development without paying attention to ecological protection, and ecological damage must be borne by economic assistance.

◎ Forests have great functions of soil and water conservation.

According to the research, as long as there is a litter layer of 1cm in the woodland, the sediment loss can be reduced by 94%. The sediment transport per hectare of forested land is 0.05 tons, and that of forested land is 2.22 tons, with a difference of 44 times. Forest ecosystem is a barrier to wind and sand fixation.

◎ Forests have the function of preventing wind and fixing sand.

Its windproof benefits are shown in two aspects: reducing wind speed and changing wind direction. The shelterbelt with sparse structure can reach 3-5 times the height of the windward forest belt and 25 times the height of the leeward forest belt. In the windproof range, the wind speed is reduced by 20%-50%. If the forest belt and forest network are properly arranged, disastrous gale can be turned into breeze. The roots of trees, shrubs and grass can fix the soil.

Forest ecosystem can meet human health and spiritual needs.

The purpose of economic development is to improve people's quality of material, cultural and spiritual life. The deterioration of people's health caused by environmental pollution is still borne by the economy. Forests, trees and grasslands have the functions of purifying air, reducing and controlling pollution and satisfying people's physical and mental health and spiritual enjoyment. It can be said that forests and grasslands are the protectors of people's healthy body and high-quality life.

The contribution of forests to economic development is not limited to the above aspects, but also many. These include:

It is the fundamental way to revitalize the mountain economy. China's mountainous areas account for 69% of the land area, and its population accounts for13 of the total population of China. Comprehensive development and poverty alleviation in mountainous areas have become one of the main battlefields of national economic and social development. According to the characteristics of mountainous areas, the mountain must be treated first, and the forest must be promoted first. Grasping the leading role of forestry will enliven the economy and ecology of mountainous areas.

It is an important industrial sector of the national economy. Wood is recognized as one of the four major raw materials in the world and has a wide range of uses.

This is a natural reservoir. According to scientific calculation, when the root system of trees in the soil reaches 1 m depth, the forest can store 500-2000 cubic meters of water per hectare, and the forest can absorb 20-40 tons of rainwater per square kilometer, which is about 20 times that of woodland. When there is a lot of rain, the forest can store water. When there is little rain, the forest can slowly release water, which is simply a huge natural reservoir.

Wonderful green leaves-the influence of plants on the environment

Yin Xuebo, Assistant Researcher of Beijing Botanical Society

Rain and dew moisten seedlings, and everything depends on the sun. Where did the beautiful environment come from? The green leaves of plants played an important role. Let me talk about the important role of green plants in the earth environment on which human beings depend, especially in the urban environment.

It is estimated that the annual incident solar energy of the earth is 5.4x 1024 Joule, and the annual fixed solar energy of green plants is about 5x 102 1 Joule. These energies are the energy base on which all heterotrophs, including human beings and various animals, depend. In addition, 3 billion years ago, the CO2 content on the earth was about 9 1%, and there was almost no oxygen, which was not suitable for human survival at all. It took about 300 million years to reach the modern level, all because of the role of green plants. According to the measurement, every hectare of forest and park green space releases 750 kilograms and 600 kilograms of oxygen every day in summer. Global green plants release about 1000 billion tons of oxygen every year. An adult breathes more than 20,000 times a day, inhales 15-20 cubic meters of air, and consumes about 0.75 kg of oxygen. According to this calculation, urban residents need 10 square meters of woodland to provide the required oxygen, which is provided by well-grown lawns.

Fixing CO2 and synthesizing organic matter. According to the measurement, each hectare of forest and park green space can absorb and fix 65,438+0,050 and 900 kilograms of CO2 per day respectively (green plants also breathe and release CO2, but the amount of CO2 released by photosynthesis in the sky is more than 20 times). The annual net production of dry organic matter of all plants on the earth is about1.5-200 billion tons. This is the basic material for human beings and heterotrophs to survive in the world. At present, the concentration of carbon dioxide in the earth's air exceeds 0.036%, while it was only 0.028% before 100. However, in the future, the concentration will accelerate and the greenhouse effect will make the sea level rise, and many disasters will occur frequently.

Wind and sand fixation, accelerate dust reduction. The construction of shelterbelt in the wind disaster area can reduce the wind speed by about 30% within the protection range; The yield of farmland with shelterbelt is about 20% higher than that without shelterbelt. Chifeng City, Inner Mongolia has been afforested for 40 years 1 10000 mu, with nearly a thousand fixed sand dunes. The number of sandstorm days is reduced from 3.7 days to 1.5 days, the number of sand blowing days is reduced from 54 days to 20 days, and the maximum wind speed is reduced from 40m/s to 17. A molded Pinus bungeana has about 6.6 million needles, and the total leaf area of an adult Tilia amurensis is more than 30,000 square meters. 165 The total length of needles of a pine can reach 250 kilometers. Such a large leaf area, coupled with some hairy structures on the leaves, has a great adsorption effect on dust. It is estimated that the dust content in the air is higher than that in the green road. The amount of dustfall above grassland is only 1/6 ~ 1/3 of bare land.

Soil and water conservation, water conservation. In densely forested areas, surface runoff accounts for less than10% of the total rainfall; At ordinary times, the canopy can intercept 15-40% of rainfall; The water holding capacity of litter can reach 2-4 times of its own dry weight; Each hectare of forest soil can store 640-680 tons of water; 50,000 mu of forest is equivalent to a reservoir with a storage capacity of 6,543,800 cubic meters. Scientists have observed that the soil erosion of woodland with 30% forest coverage is 60% less than that of woodland without forest. Some people have observed the mountainous area with a slope of 13 degrees, and found that the soil erosion of bare land is 48 times that of woodland. According to the study of Miyun Reservoir Basin by Beijing Forestry University, under natural rainfall, the sediment yield of barren slope is 4- 12 times that of Robinia pseudoacacia forest land and 9-44 times that of Pinus tabulaeformis forest land. During the Great Leap Forward, the forests of Wanglong Commune in Cangxi County, Sichuan Province were completely cut down. After afforestation, the coverage rate recovered to 30%, and the rainfall in 198 1 two days was 290 mm, so there was no disaster. 1996, Xingtai, Hebei, Handan and other places were hit by heavy rain, and many farmland in Taihang Mountain area suffered devastating damage. However, due to the construction of soil and water conservation forests and economic fruit terraces in Qiannanyu Village of Xingtai, it is still a bumper harvest scene.

Regulate climate and increase precipitation. A medium-tall eucalyptus tree absorbs nearly 4 tons of water from the soil a year; In a summer, each tree will transpiration an average of 2 tons of water; The air humidity over the forest is 10-25% higher than that in non-forest areas and 5- 10% higher than that in farmland. According to the calculation of transpiration of 8000 tons of water into the air per hectare, it will consume about 4 billion kilocalories. According to the measurement, the ground temperature of green land in summer is generally 10- 17 degrees lower than that of square white land and 12-22 degrees lower than that of asphalt road. In winter, the average temperature of lawn surface is 3-4 degrees higher. According to statistics, the rainfall in forest land is higher than that in non-forest land 16- 17%, and the lowest is 3-4%. In Russian forest areas, the average annual precipitation can be increased by 1%-25%, and in the southern plains of India, afforestation can increase the local annual precipitation by 65438+. Forests can increase precipitation by 2%-5% on average. If the increase of atmospheric condensate by forests is included, forests can increase the average precipitation by 65,438+00%. Some scholars believe that after greening in northwest China, the precipitation can be increased by 1 10mm, which can greatly alleviate the problem of drought and water shortage in northwest China.

Absorb poisons and kill germs. Cryptomeria fortunei forest can absorb about 60 kilograms of sulfur dioxide per month, and the absorption of citrus forest is twice that of Cryptomeria fortunei. Each hectare of Robinia pseudoacacia forest and Betula platyphylla forest can absorb 42kg of chlorine and 0/2 kg of fluorine per year. It is reported that Chlorella vulgaris is usually stored for 48 hours in a sewage temporary storage box, and the purified sewage can be used for farmland irrigation. Planting reed in the experimental pond can reduce phosphate, organic nitrogen, ammonia nitrogen and suspended matter in water by 20%, 60%, 66% and 30% respectively. 1 ha Eichhornia crassipes can absorb 4 kg of manganese, 34 kg of sodium, 22 kg of calcium, 89 g of mercury, 297 g of nickel, 32 1 g of strontium and 0/04 g of lead. From the water overnight. Experts from Institute of Botany, Chinese Academy of Sciences have made great progress in removing heavy metal pollution with plants.

It has been found that more than 300 kinds of plants can secrete volatile bactericidal substances; 1 mu pine forest can secrete 2 kg of bactericide every day; There are 4 million bacteria per cubic meter of air in crowded shopping malls, 580,000 in boulevards, 1 0,000 in green parks and only 55 in forest areas. Fresh peach leaves can drive away bedbugs. The smell of cucumber can make cockroaches run away; Onions and tomatoes can drive away flies; Wooden cordate telosma or basil can repel mosquitoes.

Indicating plants and monitoring the environment. Using highly sensitive plants can monitor air pollution and pollutants. When the concentration of SO2 in the air reaches 1-5 ppm, people can smell it, while alfalfa will have symptoms when it reaches 0.3ppm. In a clean environment, the fluorine content of peach leaves is about 10mg/kg, but it will cause injury symptoms when it reaches more than 50mg/kg. Gladiolus is harmful to fluoride.

Reducing noise is beneficial to people's health Experiments show that the explosion of 1.5 kg TNT explosive can travel 4 kilometers in the air, but only 40 meters in the forest. The experimental results show that the forest belt with the width of 10 meter can reduce the noise by 30%. 250 square meters lawn can attenuate sound 10 decibel; According to the measurement, the forest in the city park can reduce the noise by 26-43 decibels, and the greening street can reduce the noise by 10-20 decibels compared with no greening; Leave a 5-7m wide zone between the houses along the street and the street to plant trees for greening, which can reduce vehicle noise15-25db.

Rich and colorful, beautify life. Plants are the best materials for greening and beautifying urban and rural areas. Colorful plant flowers and the fragrance of many plants give people a pleasing feeling. For example, the fragrance of chrysanthemum is effective for headaches, dizziness and colds. In addition, the fresh air in green space and forest is rich in negative oxygen ions, and the air in forest can reach more than 20 thousand per cubic meter. However, there are only 40-50 negative oxygen ions in urban indoor air. Negative oxygen ions can give people a fresh feeling and have a certain therapeutic effect on lung diseases. According to the investigation, the accident rate is reduced by 40% and the work efficiency can be increased by 65,438+05-35% in places with beautiful green environment. Beautiful environment can also greatly stimulate people's creative inspiration.