Why are some street trees suitable for planting on municipal roads but not in residential areas?

In landscape design, people-oriented and users' feelings and experiences are often emphasized. Design concepts can not only stay at the conceptual level, but also convey or realize these concepts through design details. In the plant planting design, adding a row of street trees can solve the contradiction between the increasingly hot weather and the shady site, improve the comfort of users and reduce the above-mentioned spit.

Street trees are trees planted in a certain way on both sides of urban roads, which play a shading role and are often used in municipal roads. The Technical Specification for Planting and Maintenance of Street Trees in Shandong Province requires that street trees should be planted on sidewalks with a width greater than 2.5m m. However, with the increase of the space area of newly-built public green space and the increase of the green rate in residential areas, the planting design of street trees in some non-municipal road greening scenes has been paid more and more attention.

Municipal roads and residential areas plant the same street trees. Due to different application scenarios, there are some differences in planting design:

1? choice of tree species

Taking common tree species in Zhengzhou as an example, street trees in residential areas can choose Sophora japonica, Ginkgo biloba, Fraxinus chinensis, Cinnamomum camphora and Bauhinia chinensis. However, some tree species, such as Chongyang, Aesculus chinensis, Magnolia grandiflora, etc., have large crown and strong shade, but after transplanting, the seedling stage is long and the branch germination and branching ability is weak, so it is not suitable to form a full crown, and the immediate effect is not good. It will affect the overall look and feel when handing over the house, and it is generally not commonly used.

Toona sinensis, Huangshan Luan and Fatong are commonly used street trees in municipal roads, but they are not commonly used in residential areas.

The new leaves of Toona sinensis can be made into delicious food. If used in residential areas, it is easier to be picked and eaten. Picking seedlings artificially not only destroys the normal growth of seedlings, but also increases the difficulty and safety risk of property management.

Huangshan Luan tree is umbrella-shaped, with beautiful flowers and fruits. However, it is easy to suffer from serious honey worms, which secrete a lot of oily substances and are sticky. If used in residential areas, oily substances will pollute the road surface when dripping. The owner feels uncomfortable when he walks. If pesticide treatment is carried out, the green space of the community is relatively closed, the owners are exposed for a long time, the immunity of the elderly and children is relatively poor, and the pesticides in the air will cause certain harm to the body. However, when planted in the central separation zone of municipal roads, especially urban main roads, it has little impact on pedestrians. Therefore, it is an important factor to consider in the planting design of residential areas not to use tree species that are prone to pests and diseases.

Aconitum is not suitable to be widely used in residential areas because of its secondary harm and easy to cause respiratory infection.

Ginkgo biloba and Cinnamomum camphora are often used as street trees in residential areas, but not for municipal roads.

Ginkgo biloba is a fleshy root. In the first few years after planting, it needs high care and management. On the other hand, urban street trees are planted in strips, and the area of seedlings that need to be maintained is not concentrated, and the operation line is long. The maintenance operation is often disturbed by the traffic of vehicles, and the frequency and intensity of maintenance management are not as good as those of residential areas. In addition, there are a lot of automobile exhaust on the road, and the air quality is poor, which also has a certain impact on the growth of Ginkgo biloba.

Cinnamomum camphora is a marginal tree species in Zhengzhou area. It can grow under the microclimate conditions of lee and sunshine in residential areas. For Cinnamomum camphora transplanted in that year, a windbreak wall can be built in the main wind direction to prevent cold. On municipal roads, there is no shelter from buildings and structures, and they are often in the tuyere, and there is no obvious main wind direction. It takes a lot of manpower, material resources and financial resources to set up wind barriers. There are hidden dangers in traffic routes blocked by tall wind barriers, and there is no safe solution.

2? bifurcation

Because of the traffic demand, municipal street trees can't block the line of sight, and the branch points are generally 2.8m, 3m and 3.2m Most residential areas are separated by people and vehicles, and vehicles don't need to pass through. The branch points can be relatively low, preferably 2.5m. Of course, the design of the branch points should also be determined according to the width and design intent of the road. The space surrounded by high branch points is relatively open, while the space surrounded by low branch points is relatively private.

3? space

Street trees generally choose trees with DBH greater than 20cm, and the crown width is 3-4 m, and the spacing should be set according to the crown width of the designed tree species, so as to reserve a certain growth space (generally 0.5- 1m) and not overlap the crown.

In general, the width of small car lanes on urban main roads is 3.5m, and the width of large car lanes or mixed lanes is 3.75m. The roads with median are at least two-way four lanes. Street trees are located in a large space, usually as background forests. Planting spacing is often 4-6m, which is relatively dense. The space under the forest is highly breathable, and the obstacles to air circulation are relatively small.

In residential areas, the planting spacing of street trees should not be too small, usually 7-8m. If the spacing is too small, the immediate effect will be good, and the shade will be dense after completion. However, the crown and crown cross each other, and the cross branches do not shine, so the growth potential is weakened.

From the whole life cycle of the project, the later maintenance and management is more difficult. For the branch-to-branch part, if pruning, it is difficult to work at high altitude and the cost of pruning garbage removal is high; If you don't prune, the total amount of leaves will be large, and the probability of pests and diseases will increase; The upper trees have high planting density and high canopy density. Most of the sunlight is blocked, so that the flowers, shrubs and ground cover seedlings in the lower part can not get enough light, and their growth potential becomes weak; The soil is also deprived of light, and pests and diseases breed.