1. 1 beautification function
Street green space covers the bare ground, reflects pavilions, rocks and water bodies, shows the pastoral features of the city, sets off the gorgeous space, colorful colors and aesthetic effects of modern cities, gives people a sense of tranquility, makes people open-minded, relaxed and unrestrained, and cultivates their sentiments.
1.2 ecological function
The first is to improve the climate. Street green space is a good air conditioner. Where there is green space in the city, the temperature is obviously lower than where there is no green space. This is because green plants block direct sunlight and transpiration. In summer, the temperature in the green area is 3-5℃ lower than that in the non-green area (it can be increased by 2-4℃ in winter), which is about 10℃ lower than that in the building area. According to the calculation, the urban temperature can be reduced by 0. 1℃ for every increase of green area.
The second is to purify the air. Urban green space has the same detoxification function as human liver. Large areas of trees and grasslands can block the climate, thus reducing the wind speed and depositing some pollutants in the air. According to the measurement, the rate of bacteria in the air of city department stores is 400 times higher than that of parks and 654.38+ 10,000 times higher than that of forest areas. There are 3.5 bacteria per cubic meter of air in forest areas, while there are as many as 34,000 in densely populated cities.
The third is to reduce noise. Noise is harmful to human health and has become a social hazard in cities. 40-meter-wide forest belts can reduce noise by 10- 15 decibels, and forests in urban parks can reduce noise by 26-43 decibels. On the street without trees, the noise is five times louder than on the street with trees.
The fourth is to protect soil and water. Green land has dense surface cover, underground trees and grass roots, so it has good soil consolidation effect. According to reports, only 1/4 of the grass-covered area has lost soil. According to the calculation of relevant departments, the average water storage per mu of green land is about 20 cubic meters more than that of bare land. As far as10 million mu is concerned, the green area is undoubtedly a huge underground "reservoir".
The fifth is the producer of oxygen that people need. The oxygen that people need to sustain life is that green plants absorb CO2 in the air and release it through photosynthesis.
1.3 social functions
The first is to provide residents with rest space. The soft green carpet gives a pleasant feeling. Green spaces planted in hospitals, residential areas, parks, squares and other places are places for people to work, study, rest and rest after work, especially suitable for the elderly over 60 years old and children under 10 who account for 20-30% of the population.
The second is to regulate human physiological functions. In modern society, the pace of work and life is accelerating, and people's mental state is highly tense, so they need to relax after a day's work and study. Beautiful green environment and fresh air can effectively prevent the breeding of germs, and the green environment is conducive to the rehabilitation of patients with hypertension, neurasthenia and heart disease.
The third is to improve the city appearance and investment environment. A beautiful, clean and green modern city can not only greatly improve the quality of life of residents, but also reflect the taste and spiritual civilization of a city. Thereby improving the investment environment. Dalian's experience is a good proof. In the past five years, Dalian has invested 5 1 100 million yuan in urban environmental construction, more than the sum of the past 50 years. Dalian has taken this road of environmental and economic development, although it was opposed by many people at first, thinking that ordinary people can't even live in houses, so what environmental management is there! But now no one has made any criticism, because they have accepted the idea that a city is valuable only when the environment is good and the grade of the city is improved. Therefore, the Dalian municipal government believes that greening, purifying and beautifying the city is not only an environmental problem, but also an economic problem.
2 urban greening should follow the laws of plant physiology and ecology
2. 1 We should follow the law of "livable environment" in the city and do a good job in the overall planning and community layout of urban tree planting and greening. Modern cities are generally characterized by "three more and one less", that is, more people, more houses, more cars, and less available land and public space. Then, in order to provide a good living and leisure environment for urban residents and tourists, it is necessary to expand the area of green space and plant as many trees and flowers as possible in a limited space. The contradiction between the limited land and space and the increasing environmental demand must be solved through scientific and reasonable planning. It is one of the goals that modern urban planning should pursue to increase green belts and plots by building urban forests. Where trees, flowers and grass can be planted within the planning scope, community planning and detailed planning should also be done to optimize and beautify the whole environment, and efforts should be made to make the environmental benefits, ecological benefits and input costs of urban tree planting and greening tend to be satisfactory to the citizens.
2.2 Follow the ecological law of "plant community" and make a reasonable combination of arbor, shrub and grass. Trees, shrubs, herbs, vines and bamboos are all important parts of the plant kingdom, all of which have their specific plant ecological functions, and each has its own role in nature, and its own internal functions cannot be substituted for each other. In urban landscaping, we should follow the physiological and ecological laws of plant communities, that is, planting trees when trees are suitable, planting trees when trees are suitable, and planting grass when grass is suitable, so as to overcome the current one-sided mentality of "being greedy for foreign countries", pay attention to the reasonable collocation of trees, shrubs and grass, use vigorous and beautiful weeds for various trees and lawns, save maintenance and watering costs, and improve greening benefits.
2.3 We should follow the law of "plants adapt to climate" and grow in suitable seasons and environmental conditions as much as possible. In the long-term growth and development process, plants have formed their own responses to the rhythmic changes of external climate, temperature and water. Trees, flowers and plants generally belong to higher plants, which have phenological stages such as germination, growth, budding, flowering, fruiting, fruit ripening, defoliation, dormant growth and development. Only by using, recognizing and understanding these phenological stages can human beings achieve good results. Generally speaking, it is wise to transplant trees when they are dormant. Transplanting plants in bud or high temperature season will interfere with the normal growth and development of plants. Especially deciduous broad-leaved trees, should not be transplanted after flowering and leaf release. Therefore, cities should determine the suitable planting and greening period according to the changing law of local seasonal temperature.
2.4 Should follow the law of physiological balance of single plant, and try to keep a proper amount of branches and roots of green plants per plant. At present, in the process of urban tree planting and greening, the "broken arm" and "broken head" of transplanted trees have seriously damaged the growth and development of trees themselves objectively, delaying their proper greening and shading effects. We should treat every plant and tree from the viewpoint of plant physiology and biology. When transplanting trees, we should pay attention to keeping proper roots according to the size of the trees, especially keeping as many fine roots and root hairs as possible, so as to better absorb water and nutrients. Attention should be paid to the proportion of aboveground and underground parts in conifer transplantation. In order to improve the survival rate, the branches at the lower part of the crown should be trimmed appropriately to reduce the consumption of water and nutrients. For budding tree species, in order to reduce transpiration and improve survival rate, a large number of branches and leaves are cut off to rejuvenate and sprout new vitality. This kind of "shaving" is necessary. In a word, we should cherish and respect the growth and development rights of trees to the maximum extent.
2.5 We should follow the law of "photosynthesis" of plants, and try our best to reduce the improper intervention of artificial strong light on urban trees and flowers. The green plants in modern cities, whether they are urban parks, street greenbelts, street greening trees or small gardens on the roofs of residents, are the products of plant photosynthesis. Further analysis of the regional scale of urban landscaping is heterogeneous "introduced patches". These plaques are more easily noticed, so they are very fragile. Worryingly, some city managers deliberately set high-power spotlights or colored lights to illuminate at night, making them emit green light all night. As everyone knows, this artificial dazzling behavior not only directly forms the "stress" of strong light on plants, but also interferes with the normal alternation of day and night and the growth and development of plants. At the same time, it directly hinders the normal habitat and dormancy of birds and insects living in trees, flowers and green spaces, and affects the harmonious coexistence of plants and animals. Therefore, in urban landscaping areas, artificial power supply should be avoided as much as possible, and the natural environmental factor-solar energy should be designed and used well.
3 green plant landscape design principles
The plant landscape design of street green space should also follow the basic principles of painting art and gardening art, namely, the five principles of unity, harmony, balance, rhythm and proportion:
3. 1 unification principle: also known as change unification principle or diversity unification principle. When designing plant landscape, there should be some differences and changes in tree shape, color, lines, texture and proportion to show diversity, but at the same time, it should maintain certain similarity, arouse a sense of unity, and be vivid and harmonious. If there are too many changes, the whole will appear chaotic, and even some parts will feel fragmented and lose their beauty. Too complicated colors can make people upset and lose their way, but they are straightforward, unchanging and monotonous. Therefore, we should master the principle of seeking change in unity and seeking unity in change.
Repetition method can best reflect the unity of plant landscape. For example, in the green belt of street trees, the same species should be planted at equal intervals. Trees of the same age, or shrubs of the same age planted under trees, have the greatest sense of unity in this precise repetition.
3.2 the principle of harmony: that is, the principle of coordination and contrast. When designing plant landscape, we should pay attention to mutual connection and cooperation, embody the principle of harmony, and make people have a soft, calm, comfortable and pleasant aesthetic feeling. Find similarities and similarities, plant them together, and create a sense of harmony. On the contrary, differences and changes can produce contrast effects, produce a strong sense of stimulation, and form a feeling of excitement, enthusiasm and unrestrained. Therefore, in plant landscape design, contrast is often used to highlight the theme or attract attention.
In terms of color composition, any primary color of red, yellow and blue is mixed with the other two primary colors to form complementary colors, thus producing bright, dark, cold and hot contrast colors. When they are juxtaposed, they are mutually exclusive and have a strong contrast, showing a refreshing effect. Used well, it can highlight the theme and contrast the atmosphere. For example, red and green are complementary colors, yellow and purple are complementary colors, and blue and orange are complementary colors. A little red in evergreen trees commonly used in China's gardening art is an example.
3.3 Balance principle: This is a layout method of plant collocation. If plant species with different volumes and textures are planted according to the principle of balance, the landscape will be stable and pleasing to the eye. For example, plant species with strong colors, huge volume, large quantity, thick texture and dense branches and leaves give people a heavy feeling; On the contrary, plants with light color, small volume, simple quantity, soft texture and sparse branches and leaves give people a light feeling; According to the surrounding environment, planting has regular balance (symmetry) and natural balance (asymmetry).
3.4 Sense of rhythm and principle of sense of rhythm: Regular changes in planting will produce a sense of rhythm. There are many rhythms and rhythms in landscape composition, and the common ones are: simple rhythm; Alternate rhythm; Ups and downs, twists and turns; Mimic rhythm, etc. Yun Qi Bamboo Trail is surrounded by towering bamboo forests. If you plant a tall Liquidambar formosana at a distance of 50m or 100m, when you walk along the trail, it will not be monotonous, but will change rhythmically.
3.5 Principle of proportion and scale: Proportion and scale are one of the basic concepts of landscape composition, which directly affect the landscaping and layout of landscape. Proportion refers to the relationship between the space, shape and volume of garden scenery and its components. Scale refers to the measurement relationship between the height and activity space of scenery and people.
All kinds of garden scenery do not exist in isolation, but are intertwined. Inevitably, they will be compared with each other in terms of body shape, height and so on, showing a certain proportional relationship. A well-proportioned landscape is pleasing to the eye, and the size of the scenery is appropriate, and the master and slave are clear. Improper proportion makes people feel uncomfortable and even messy. A good proportion is an appropriate proportion to make different parts form a harmonious whole, but there is no exact specific standard or numerical value to judge. This requires designers to ponder architecture, painting and natural mountains and trees through long-term study and cultivation, and cultivate their ability to identify correct and appropriate proportions. Only when the proportion of the layout is beautiful and pleasing to the eye can it conform to the principle of "beauty" of garden scenery. To achieve a truly beautiful proportion, we must conform to the law of proportionality. The layout of the landscape should not be divorced from the practical scale, but should pursue simple and beautiful proportions. Generally speaking, if the scale of artificial scenery exceeds the scale that people are used to, it will make people feel magnificent; If the scale is normal, it is natural and cordial; If the scale is small, it is light and interesting.
Four principles of tree species selection in northern urban green space
The selection of tree species is an important part of urban street greening, because the main material of greening is trees, which need years of cultivation and growth to achieve the expected results. Proper selection of tree species and vigorous growth of trees will give full play to the greening benefits. If you make a mistake and the trees grow badly, you have to change the tree species many times. If the urban greening is not improved for a long time, the seedling raising situation in the nursery will also be affected, which will waste time and lose money. The selection of tree species in urban green space in northern China should follow the following principles:
4. 1 should basically conform to the natural laws of forest vegetation areas. Combining arbor, irrigation and grass,
That is, the natural laws displayed in the geographical area of forest vegetation in this area, we should imitate nature with reference to the trend of wild vegetation in the suburbs, so that plants can grow in the natural living environment. The main body of urban greening should be deciduous trees. Only in this way can we play a protective role, beautify the city and form its own characteristics. In addition, in order to reduce the pollution of flying flocs produced by some deciduous trees, attention should be paid to the selection of male plants when selecting such tree species (such as poplar, willow and mulberry).
4.2 The principle of giving priority to native tree species, supplemented by exotic tree species. Native tree species have strong adaptability to local soil and climate and local characteristics, and should become the main tree species for urban greening. Taking Puyang as an example, because Puyang is located in the North China Plain, it is decided that the garden trees in the urban area can only adapt to the northern climate. In order to expand the provenance, we should actively introduce some exotic tree species which are scarce in the local area, can adapt to the local climatic conditions, and have high economic value and ornamental value. But it must be domesticated and introduced before it can be popularized and applied. Such as loquat, Phyllostachys pubescens and Viburnum americanum, have been successfully introduced and domesticated in our city.
4.3 Choose tree species with strong resistance. Strong stress resistance refers to tree species that are resistant to pests and diseases, not barren, and adapt to urban "three wastes". Choosing this tree as the main tree species in the city will undoubtedly enhance the greening benefits of the city. However, tree species with strong resistance are not necessarily ideal in tree potential, posture, leaf color and flowering period. Therefore, while selecting a large number of tree species with strong stress resistance, we should also select those tree species with straight trunk, dignified posture, beautiful tree body, lush foliage, large crown, strong shade and gorgeous colors for configuration. Only in this way can we form a "colorful" greening effect.
4.4 Combination of fast-growing trees and slow-growing trees. Fast-growing tree species have good early greening effect and are easy to shade, but their life span is short, and they tend to age after 20-30 years. Slow-growing trees grow slowly in the early stage and the effect of urban greening is slow. Because of the long winter and short plant growth period in the northern region, choosing fast-growing tree species will form greening effect in a short time. Especially for street greening, we should choose fast-growing, pruning-resistant and easily transplanted tree species. Fast-growing tree species are prone to aging and premature aging, which can be solved by crown regeneration and seedling raising. The purpose of selection is to continuously select tree species with excellent properties and eliminate tree species with poor growth, poor stress resistance and poor greening and beautification effect.
4.5 Configuration principle of cultivated plants. In a specific cultural environment, through various plant configurations, landscaping has a corresponding cultural environment atmosphere, forming different kinds of artificial plant communities based on cultural environment. Thus, people have a sense of landscape between various subjective feelings and macro-environment, that is, the so-called "scene blending", that is, people accept the cultural information transmitted by plant communities through their senses, which makes people feel emotional and causes * * * sounds and associations.
4.6 Principles of environmental protection and fitness plant configuration. Can produce the ability to enhance physical fitness, prevent diseases or treat diseases, and use ecology to rationally distribute communities.
5 tree species selection of garden green space
Because of its different functions, uses, geographical environment and climate characteristics, garden green space also has its own characteristics in tree species selection.
5. 1 Parks and scenic green spaces: The selection of tree species should be as colorful as possible. According to the ecological community model of large and small trees, large and small shrubs, perennial roots, ground cover and lianas, according to the local natural conditions and microclimate environment characteristics, make full use of native tree species and successful exotic tree species to simulate nature and return to nature. At the same time, in the selection of tree species, factors such as hue, season and growth cycle should also be considered to maintain good ornamental effect and long life cycle of scenic spots.
5.2 Road green space: Due to the poor environmental conditions on the road, high content of smoke and harmful gases, strong road radiation and other factors, tree species used for street greening should be selected with large crown, shade, strong dryness, strong anti-pollution ability, pruning resistance, less pests and diseases and long life. For example, street trees can use Platanus acerifolia, Platanus acerifolia, Ailanthus altissima, weeping willow, Melia azedarach and other tree species, which can play a better sound insulation and dust retention effect. For the isolation belt located in the middle of the road, small shrubs can be densely planted, and plants such as Buxus macrophylla, Ligustrum lucidum, Ligustrum lucidum and Chinese rose with strong branches and pollution resistance can be selected to form an isolation belt with dense branches and leaves, which can better purify the air and reduce noise; You can also use flowering shrubs with strong resistance, such as hibiscus, purple leaf plum and other tree species planted in the isolation zone, but you should pay attention to the permeability of its line of sight and the choice of fixed stem height, which can also play a better street greening effect.
5.3 Protective greenbelt: We should pay attention to selecting tree species with strong wind resistance, fast growth, long growth period and long life, preferably native tree species: preferably tree species with spires or pillars and small leaves. For example, poplar, willow, Fraxinus mandshurica and Tamarix are all suitable for windbreaks in North China.
5.4 Courtyard Green Space: courtyard greening has its own characteristics in tree species selection because of its different functions and uses. In recent years, after a lot of investigation and study, we found that the purification ability of plants to absorb air pollution is as follows:
(1) In hospitals and sanatoriums, there are conifers, cotinus coggygria, Euonymus japonicus, acacia, Robinia pseudoacacia, Rosa rugosa, Magnolia grandiflora and Osmanthus fragrans. The volatile substances secreted by these trees have a strong bactericidal effect.
(2) In the heavily polluted factory area, according to the different harmful substances in the air, tree species with different detoxification functions can be selected to reduce the content of toxic substances in the air. Such as resistant poplar, Ailanthus altissima, Robinia pseudoacacia, Buxus macrophylla, Flos Caryophylli, Salix matsudana, Fructus Jujubae, Rose, Fraxinus mandshurica, Pterocarya stenoptera, Fructus Forsythiae, Elm, Broussonetia papyrifera, Cotinus coggygria, Sophora japonica, Pinus tabulaeformis, Robinia pseudoacacia, Platycladus orientalis, Flos Lonicerae, Fraxinus mandshurica, peach, etc. , with strong SO2 absorption capacity; Elm, Tilia amurensis, Crataegus pinnatifida, Jujube, Pterocarya stenoptera, Xanthoceras sorbifolia, Willow, Ailanthus altissima, Buxus macrophylla, Fraxinus mandshurica, Lonicera japonica Thunb, Larix gmelinii (Larix gmelinii in conifers is a tree species with high chlorine absorption capacity), etc. Jujube, elm, mulberry, Ailanthus altissima, Salix, Sabina vulgaris, Platycladus orientalis, Pinus bungeana, Sha Song, Prunus tomentosa, Larix gmelinii, Paulownia, Platanus acerifolia, Buxus macrophylla, Ligustrum lucidum, Zelkova schneideriana, weeping willow, etc. Strong ability to absorb hydrogen fluoride; Tree species with high lead absorption are mulberry and elm.
(3) For factories with high dust content, trees with strong dust retention can be selected, such as elm, Pu Shu, hibiscus, Magnolia grandiflora, Ligustrum lucidum, Buxus macrophylla and Robinia pseudoacacia.
(4) Trees with good sound insulation effect can be selected in the factory area with high noise, such as cedar, cypress, Metasequoia glyptostroboides, Platanus acerifolia, weeping willow and spruce. Reduce the harm of noise to human body.
(5) In primary and secondary schools and kindergartens, you can choose more ornamental tree species, such as viewing stems, leaves, flowers, fruits and some colorful plants to cultivate children's observation and imagination. In these places, we should try to avoid using tree species with thorns and secreting harmful substances, such as red Berberis and oleander, to prevent accidents.
(6) Some flower plants that are most suitable for indoor cultivation, such as giant bamboo, can absorb a lot of CO2 at night. In addition, cactus, cactus, arrow leaf and epiphyllum, various orchids of Orchidaceae, Clivia, Narcissus and Bauhinia of Amaryllidaceae all have this peculiar function. Canna has a strong ability to absorb SO2. Putting one or two pots of pomegranate indoors can reduce the content of lead in the air and absorb sulfur, hafnium and mercury. Dianthus can absorb SO2 and chloride. Roses and roses can absorb more harmful gases, such as HS, HF, phenol and ether. Chlorophytum and aloe can eliminate formaldehyde pollution. Plants such as crape myrtle, jasmine and lemon can kill protozoa, such as diphtheria and dysentery bacteria. The fragrance of jasmine, carnation, lily of the valley, violet, rose, osmanthus and other plants has obvious inhibitory effect on the growth and reproduction of mycobacterium tuberculosis and staphylococcus. Hupilan, Huweilan, tequila, palm and cultivated pineapple can purify the air at night. Orchids, osmanthus fragrans and osmanthus fragrans are natural vacuum cleaners, and their cilia can intercept and absorb suspended particles and smoke in the air.
To sum up, the purpose of urban landscaping is to create a beautiful and green environment for people's life, work and study, that is, to produce better ecological benefits. Therefore, in the greening construction of street green space, we should follow the principle of biodiversity, keep native species as much as possible, strive to build a sustainable biological community, and do a good job in plant configuration, so that it can give full play to its functions and better serve mankind.