The lace design picture of the fourth grade green handwritten newspaper

Fourth-grade afforestation handwritten newspaper lace design picture 1 Fourth-grade afforestation handwritten newspaper lace design picture 2 Fourth-grade afforestation handwritten newspaper lace design picture 3 Significance of Arbor Day

Afforestation can not only green and beautify homes, but also play a role in expanding forest resources, preventing soil erosion, protecting farmland, regulating climate and promoting economic development. This is a grand project for the benefit of present and future generations. In order to protect forestry resources, beautify the environment and maintain ecological balance, many countries in the world have set up Arbor Day according to their own actual conditions. With the enhancement of people's awareness of environmental protection and their active participation in afforestation activities, our living environment will be continuously improved.

Some foreign scholars have calculated the ecological value of trees: a 50-year-old tree produces about 365,438+0,200 dollars worth of oxygen; Absorbing toxic gases to prevent air pollution, worth about $62,500; Increase the value of soil fertility by about $365,438+$0,200; The water saving value is $37,500; Providing breeding grounds for birds and other animals is worth $365,438+$0,250; Resulting in a protein worth $2,500. Excluding the value of flowers, fruits and wood, the total value is about $ 196000.

Whether this calculation is accurate or not is obvious from the practical value of trees.

A tree can produce 200 kilograms of pulp. If these pulps are to produce toilet paper, there must be at least 750 rolls100g of toilet paper.

In the city, a tree can store the pollutants emitted by a car driving for one year 16 km. Many trees can absorb harmful gases, such as 1 hectare Cryptomeria fortunei forest, and can absorb 60 kilograms of sulfur dioxide every day. Others, such as Ailanthus altissima, oleander, Ginkgo biloba, Sycamore, etc., all have the function of absorbing sulfur dioxide. When the urban green area reaches more than 50%, the pollutants in the atmosphere can be effectively controlled.

Urban forests can increase air humidity, and an adult tree can evaporate 400 kilograms of water a day, so the air humidity in forests is obviously increased. According to calculation, the local summer temperature can be reduced by 0. 1% for every increase in urban green area.

Urban forest belts and hedges can reduce noise. A forest belt 30 meters wide can reduce noise by 6? 8 decibels

There are 3.5 bacteria per cubic meter of air in forest areas, while there are 34,000 densely populated cities lacking greening. Urban streets with trees contain about 80% less bacteria than urban streets without trees.

Urban shelterbelt can slow down the wind speed, and its effective range is less than 40 times of the tree height, of which 10? The best effect is within 20 times, which can reduce the wind speed by 50%.

In the farmland forest network, the wind speed can usually be reduced by 30%? 40%, relative humidity increased by 5%? 15%, increase soil water content 10%? 20%. According to the measurement, the canopy can intercept about 20% of the precipitation, which greatly weakens the influence of raindrops; As long as there is litter with a thickness of 1 cm on the surface, the surface runoff can be reduced to less than 1/4 of the bare land, and the sediment can be reduced to less than 7% of the bare land.

Compared with bare land, a hectare of woodland can store at least 3000 cubic meters more water. The storage capacity of 1 10,000 mu of forest is equivalent to a reservoir with storage capacity of 1 10,000 cubic meters, and the construction of such a reservoir requires an investment of more than10,000 million yuan.

Some experts predict that if forests are lost on the earth, about 4.5 million biological species will cease to exist, 90% of fresh water on land will flow into the sea in vain, and human beings will face serious water shortage. The disappearance of forests has increased the wind speed in many areas by 60%? 80%, hundreds of millions of people will die because of typhoons?