Keywords: urban green space; Environmental ecology; Ecological benefits; Human population
Due to the extremely serious urban pollution, the requirement for expanding the green area is getting higher and higher, and the land shortage in the city is impossible to meet this requirement. Therefore, while expanding the green space in a limited way, improving the ecological benefits on the green space has become an important means to improve the urban ecological environment. This paper puts forward that only by starting from the following three key aspects, namely "coverage rate", "the position of green space in the city" and "improving the ecological benefits in unit green space area" can the maximum ecological benefits of urban green space be fully exerted.
Keywords: urban green space; Environmental ecology; Ecological benefits; human population
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Due to the rapid economic development in recent years, the negative impact on the city-environmental pollution, has reached a point that can not be ignored. All kinds of toxic gases that harm human beings have greatly increased, and oxygen has been consumed in large quantities; Soot, dust, radioactive substances and strong carcinogens are flying all over the sky; Photochemical smog appeared in many cities in China; In cities with a population of over one million in China, the mortality rate of lung cancer has risen to the first place. In some cities, due to the influence of topographic conditions, the polluted atmosphere is not easy to disperse, and the situation is more serious; Due to the sudden increase in the number of cars in the city, the pollution of automobile exhaust is adding fuel to the fire. All these make urban residents suffer greatly, which not only reduces labor productivity, but also shortens people's working years and life expectancy. This city-centered environmental pollution continues to spread, and the scope of ecological damage is still expanding. If we don't make up our minds to carry out comprehensive improvement, the achievements of rapid economic development will be offset by the consequences of pollution. The fundamental way to solve this problem is to reduce and eventually eliminate pollution sources, but due to economic and technical constraints, it takes some time and process.
At present, China's economy is in a period of rapid development, and the degree of urban pollution is at its peak. The harsh ecological environment not only threatens people's survival, but also seriously affects the investment environment, thus hindering economic development. At this critical juncture of contradictions and conflicts, it is only when all walks of life join in this struggle and form a comprehensive joint force that it is possible to curb the continuous deterioration of the environment and make the economy develop continuously.
Landscaping workers should devote themselves to improving the urban ecological environment and realize the leap of "concept renewal" This struggle to improve the living environment of mankind is the need of the current situation. Today, some leaders and greening workers still regard urban greening as the subsidiary nature of purely ornamental and decorative cities, which is bound to be outdated. In fact, urban greening has been listed as the infrastructure of urban construction and sustainable development by the state. Urban greening is an indispensable part of improving urban ecology and improving citizens' living, working and living environment.
As we all know, plants are the original creators of human living environment. Without plants, there would be no human beings. Now, plants are regarded as an indispensable tool to improve the urban environment, and urban greening is the only effective way for all walks of life to purify the environment through "natural renewal". Urban greening workers should take the initiative to participate in this great cause related to the national economy and people's livelihood.
To sum up, today's urban greening must consider all the problems of urban greening from the perspective of maintaining urban ecological balance. Only in this way can we give full play to the ecological benefits of urban greening and achieve the purpose of reducing pollution, improving the environment and beautifying the city. Urban greening workers should establish a sense of mission and responsibility. We should not only build the scale of urban greening, but also tap the potential and increase efficiency to build the most essential connotation of urban greening, that is, good environmental quality and quality of life, not form. In order to give full play to the role of urban greening in improving urban ecology, there are the following three keys.
1, and strive to improve the urban greening coverage rate.
The first condition of urban greening is land. Our government regards protecting the environment and greening the motherland as a basic national policy, and the Ministry of Construction has formulated urban greening planning and construction indicators, stipulating that the urban green space rate will reach 25% in 2000 and 30% in 20 10. The urban green coverage rate reached 30% in 2000 and 35% in 20 10, which requires cities across the country to compile and revise the green space system planning, indicating that the China municipal government attaches importance to the urban green space index. The basis of this index has been proved by a large number of research data at home and abroad. No matter a city or a region, under normal circumstances, the green coverage rate of 30% ~ 50% is of great significance to its ecological balance, that is, if it reaches or exceeds this range, the ecological environment is expected to develop in a virtuous circle. If it fails to reach or decline, the ecological environment will inevitably deteriorate. At present, the environmental pollution in many cities in China is very serious, which has exceeded the normal state. In order to make the ecology as balanced as possible, the green coverage rate can only be much higher than this critical range, so as to effectively improve the urban environment. Expanding the green area is a very important and effective way to improve the urban ecological environment. However, at present, China's urban land use is very tight, and this method is obviously limited at present, which can not reach the green area needed to achieve ecological balance. Because of this, tapping the potential and increasing efficiency in the limited green area and changing the growth mode of ecological benefits have become an important topic facing the current urban greening work. However, this does not mean that the green area of the built-up area can never be increased. At present, some large and medium-sized cities move buildings, build new buildings and expand green squares in downtown areas with a long-term vision. Many urban greening planners have repeatedly advocated roof greening, which is an effective measure to increase urban greening coverage.
Nowadays, there are more and more permanent tall buildings in cities. Seen from a height, the roof covers the whole city. The roof area accounts for at least 1/3 of the urban built-up area, and these roof textures have played a great role in the deterioration of urban ecology, especially in summer, the roof absorbs and releases a lot of solar radiation, which makes the indoor and outdoor temperatures rise. In some countries, roof greening has also been included in urban modernization, which is undoubtedly considered from the ecological environment. All localities only need to further study policies and carry out pilot promotion according to the situation of their respective cities. Roof greening is not only quick, low-cost and good in greening effect, but also an effective way to improve urban greening coverage, especially to improve urban ecological benefits. It not only reduces the area of deteriorating environment, but also increases the green plants of the same area.
2. Plan the location of green space scientifically and reasonably.
Although the existence and scale of urban green space play a primary role in improving the ecological environment, the planning position of green space in the city also plays a vital and even decisive role. For example, Jinan is a city where northeast winds and southwest winds prevail. In addition to planning a large area of green space in the upwind direction of the city, several large green spaces should be planned in the urban area from northwest to southeast, which will play an important role in improving the ecological environment of Jinan. Because of the northeast and southwest winds in Jinan, residents living in the southwest and northeast of the Botanical Garden can enjoy the fresh and clean air filtered by the green space of the Botanical Garden. If there is a large area of green space in the city center, its ecological benefits will be more obvious and its influence will be greater. No matter what wind direction, residents around the green space can benefit. The green space in the city center can also improve the urban heat island effect to a great extent and reduce the urban temperature in hot summer. If a large area of green space is planned in the northwest of the city, it will have little effect on improving the urban ecology. If, for a certain need, the green space in the city center is moved to the suburbs, or the green space in the urban area is used for other purposes, and then the green space in the suburbs is crossed to make up for the greening index of the ministerial standard, although it has reached the index, its ecological benefit to the urban area is very low. In this sense, the position of green space in the city is more important than the index of green coverage.
3. Improve the efficiency of green space ecological benefits.
As mentioned above, the first step of a city has really reached the urban greening index stipulated by the state, and the second step has been scientific and reasonable in the planning and layout of green space. Will the ecological benefits of green space be brought into full play? Actually, it is not. Because of the different plant configuration and growth conditions in the unit green space, the ecological benefits are very different, and there is great potential for tapping potential and increasing efficiency.
3. 1 area problem
The ecological benefits of garden plants, such as absorbing carbon dioxide and releasing oxygen, absorbing various toxic gases, increasing air humidity by transpiration, reducing the temperature around plants in summer, and absorbing noise and dust, are basically completed by leaf area, and the ecological benefits are directly proportional to the leaf area per unit green space. In this sense, to increase ecological benefits, it is necessary to increase leaf area. Trees, shrubs and lawns have different leaf areas. The leaf area of trees can reach about 20 times of the orthogonal projection area of the crown, while that of shrubs is only 5 ~ 10 times, and the lawn is smaller. The ecological benefit of tall trees is higher than that of shrubs and lawns; The ecological benefit of covered green space constructed by combining trees, shrubs and lawns is obviously greater than that of double-layer or single-layer green space. The same area of urban green space has different structures, and the ecological benefits produced by the combination of arbor, shrub and grass can be several times, ten times or even dozens of times that of single-layer lawn. Therefore, in order to give full play to the ecological benefits of urban green space, we must build multi-layer communities to improve the efficiency of ecological benefits of green space, and we must never win with lawns.
Special emphasis should also be placed on the role of protecting trees. First of all, tall trees in green plants have large leaf area coefficient and high purification efficiency; The effect of improving ecology and climate is remarkable. According to German botany, the ecological benefit of an adult tree is equal to 1600 small trees, which shows the great difference. Therefore, "planting big trees, seeing big green and improving big climate" is actually an important policy of urban greening work at present. Secondly, tall trees increase the vertical height and volume of multi-layer planting, thus increasing the leaf area on the unit green space and ultimately increasing the ecological benefits. Third, due to the emergence of a large number of high-rise buildings in the city, only big trees can compete with them, making the urban landscape more magnificent. However, the protection of big trees in some cities is really not optimistic. It stands to reason that urban greening began in the early 1950s when New China was founded, and there should be many big trees by now. But there are not many big trees in reality, because the protection of big trees is not taken seriously. In urban construction and old city reconstruction, it is obvious to all that many cities, including Jinan, have almost no big tree landscape, which is so disproportionate to a historic city. As far as the existing trees are concerned, their living environment is also very sinister, and the result of marketization is also great damage to green space and trees. Therefore, "protecting the existing trees and green spaces in the city is the minimum action to maintain the ecological balance of the city."
3.2 Realize the selection of greening tree species in the ecosystem.
Different tree species have different ecological functions and benefits, some of which are very different. Therefore, in order to improve the ecological benefits of green space, it is necessary to choose those resistant tree species and those with higher ecological benefits corresponding to various pollution gases. Such as arborvitae, Sabina vulgaris, Ailanthus altissima, Sophora japonica, weeping willow, Euonymus japonicus, Ginkgo biloba and so on. Tree species with strong chlorine absorption capacity include Robinia pseudoacacia, Buxus macrophylla, hedgehog, Ligustrum microphyllum, Euonymus fortunei and so on. Platanus acerifolia, Robinia pseudoacacia, Ligustrum lucidum and Buxus macrophylla can also absorb lead in automobile exhaust. In order to meet the needs of the community, shade-tolerant tree species, such as tassel, orange, gold and silver wood, pearl plum, Euonymus japonicus, Euonymus fortunei and Parthenocissus tricuspidata, were selected. In order to release oxygen and absorb carbon dioxide as much as possible, it is necessary to plant trees with strong photosynthesis. For example, weeping willows in trees have the strongest ability to absorb carbon dioxide, juniper in evergreen trees and crape myrtle in shrubs. These plants are also trees with strong oxygen release ability.
Tree species with good comprehensive ecological benefits in North China and other vast areas include: willow, elm, ginkgo, Populus tomentosa, Populus euphratica, Platanus acerifolia, Fraxinus mandshurica, Robinia pseudoacacia, Sophora japonica, Albizia Albizzia, Ailanthus altissima, Platycladus orientalis and Sabina vulgaris. In the case of serious air pollution, we should first choose tree species with strong anti-pollution ability. Only when they can survive and grow normally can they play a role in greening and preventing air pollution. If a large number of trees with good ecological benefits are used in urban green space, it will undoubtedly further improve the ecological benefits of the city.
If the urban greening planning department and the construction management department can work hard and implement the above key issues, the ecological benefits of urban greening can be fully exerted, and the growth mode of ecological benefits will be from simply increasing the area (not excluding increasing the area; As mentioned above, more efforts should be made to tap the potential and increase efficiency, and ten green spaces should be used to get twice the result with half the effort.
3.3 efforts to promote the healthy growth of garden plants
Due to the serious pollution in the city, the leaves of plants in the city are covered with a layer of pollutants to varying degrees. This layer of pollutants not only directly poisons plants, but also hinders the photosynthesis and respiration of leaves, making plants lose their self-regulation ability and their own ecological balance. In addition, due to poor management, the dual effects of the ground and underground not only cause poor plant growth, but also cause death, and its ecological benefits are very low. In order to make plants grow normally and play their normal ecological functions, it is necessary to help plants restore their own balance manually, including fine and scientific management of plants in green space, such as spraying tree crowns with clear water (or studying "green" substances such as leaf cleaner) to wash away pollutants on leaves; At the same time, timely loosening soil, fertilization, irrigation, pruning, pest control and so on. Improving the management level of green space quickly and making plants grow vigorously is one of the important contents to give full play to the ecological benefits of green space, tap the potential and increase efficiency.
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