This paper expounds the concept, scientific connotation, main functions of ecological principles and its application in ecological gardens.
Keywords: ecological park environmental protection, ecological balance, species diversity
A city is a large-scale complex dynamic ecosystem, which consists of social, economic and natural subsystems. It has the characteristics of openness, dependence and fragility, and is easily disturbed by changes in environmental conditions. In the urban ecosystem, there are both natural elements and highly artificial elements, and the garden green space system is the only one with self-purification function, which plays a very important role in improving environmental quality, maintaining urban ecological balance and beautifying the landscape. In recent twenty years, with the acceleration of urbanization and the aggravation of environmental problems worldwide, people have increasingly realized the importance of taking the road of ecological gardens and improving urban environmental quality with green space system, which has been regarded as a symbol to measure the degree of urban modernization and civilization in many countries.
Concept and scientific connotation of ecological garden
Ecological garden mainly refers to the garden green space system constructed under the guidance of ecological principles (such as reciprocal growth, niche, species diversity, competition, chemical interaction, etc.). In this system, trees, shrubs, herbs and lianas are arranged in a community according to local conditions, and the populations are coordinated with each other, with complex levels and suitable seasonal colors. Plants with different ecological characteristics can be fully utilized in their proper places. Land space, nutrients, moisture, etc. Constructing a harmonious, orderly and stable community is the highest level of urban landscaping work and the inevitable result of the development of human material civilization and spiritual civilization. With the high development of industrialization and the intensification of urbanization, it has brought the crisis of living environment to mankind. This grim reality forces people to protect the natural ecological environment and imitate the natural environment in order to seek a good living environment. Taking landscape greening as the main means, taking advantage of the favorable and unfavorable factors that have great influence on the urban ecological environment according to the situation, fully greening the living environment of human beings from the perspective of improving the land and promoting ecological balance, and pushing the cause of landscape greening to a new stage of ecological gardens. 〔 1〕
The scientific connotation of ecological park lies in: ① through scientific allocation, an artificial plant community with reasonable time structure, spatial structure and nutritional structure is established to provide people with a living environment with a virtuous ecological cycle; ② Make full use of green plants to convert solar energy into chemical energy, improve the utilization rate of solar energy and the conversion rate of biological energy, adjust microclimate, absorb toxic and harmful gases in the environment, attenuate noise and adjust ecological balance; (3) Beautify the landscape, improve the artistic level in the green environment, improve the sightseeing value, improve the social welfare benefit, improve the health care and recuperation function, and provide people with a higher level of cultural, entertainment and leisure needs and a green ecological environment for survival and development.
Second, the main functions of ecological gardens
The functions of ecological gardens are various. Generally speaking, they are mainly embodied in regulating microclimate, improving environmental quality and beautifying landscape.
Regulate microclimate
According to L.J.Batten, microclimate mainly refers to the climate from the ground to the height of 10m ~ 100m, which is the area and space for human life and plant growth. The production and living activities of human beings and the growth and development of plants have a profound influence on the microclimate.
Transpiration of plant leaves can adjust temperature and humidity and absorb solar radiation heat, which has a positive effect on improving urban microclimate. The research data show that when the urban temperature is 27.5℃ in summer, the surface temperature of lawn is 20℃ ~ 24.5℃, which is 6℃ ~ 7℃ lower than that of bare land and 8℃ ~ 20.5℃ lower than that of asphalt pavement. In winter, the surface temperature of football field covered with lawn is about 4℃ higher than that of bare ground.
Because green plants have strong transpiration and constantly transport water vapor into the air, air humidity can be improved. It is observed that the relative humidity of green space is higher than that of non-green space 10% ~ 20%, and street trees can also increase the relative humidity 10% ~ 20%.
Urban belt-shaped green space such as road greening and riverside green space is a green ventilation corridor of the city, which can introduce natural airflow from the suburbs of the city into the city and create good conditions for urban ventilation in summer. In winter, the wind speed can be reduced and the wind can be prevented.
Improve environmental quality
1 Absorb carbon dioxide, release oxygen and maintain carbon-oxygen balance. Relevant data show that each hectare of green space can absorb 900 kgo 2 and produce 600kgO2 every day, and each hectare of broad-leaved forest can absorb 1000 kgo 2 and produce 750kgO2 every day in the growing season, which can be used by 1000 people to breathe. A well-grown lawn can absorb CO2 15kg CO2 per hectare per hour, while the CO2 exhaled by each person per hour is about 38g, so if there is a 25m2 lawn or 10 m2 forest during the day, the CO2 exhaled by one person can be basically absorbed. It can be seen that in a general city, everyone should have at least 25m2 lawn or10m2 forest, so as to adjust the proportion balance of CO2 and O2 in the air and keep the air fresh. If the influence of industrial production on the proportion balance of urban CO2 and O2 is considered, the index of green space should be greater than the above requirements.
There are many kinds of toxic and harmful gases that pollute the air and endanger human health, including SO2, NOx, Cl2, HF, NH3, Hg and Pb. At a certain concentration, many plants have the ability to absorb and purify. The research shows that the concentration of SO2 decreases obviously when it passes through the forest, and Cryptomeria fortunei forest absorbs 720kgSO2 every year. Ailanthus altissima, oleander, Podocarpus, Ginkgo biloba, Ligustrum lucidum, Magnolia grandiflora and cypress all have strong absorption capacity.
Dust plants, especially trees, have obvious blocking, filtering and adsorption effects on dust. Because the crown of the tree is very strong, the leaves are wrapped and secrete viscous oil, which makes the tree have a dust retention effect.
4 sterilization because there is less dust over the green space, the bacteria attached to it are reduced; In addition, because many plants themselves can secrete a bactericide, they have bactericidal ability. According to the measurement in France, there are as many as 4 million bacteria per cubic meter of air in department stores, 580,000 in boulevards, 1 0,000 in parks and only 55 in forest areas. The difference of bacterial content in the air between forest areas and department stores is 70,000 times.
Noise-reducing plants, especially forest belts, have certain effects on noise prevention and control. According to the calculation, the noise can be reduced by 40m wide forest belt 10 ~ 15 dB, 30m wide forest belt/4.4m wide hedge/6 dB. Trees can reduce noise because sound energy is projected on branches and leaves and reflected in all directions, which makes the leaves vibrate slightly and reduces the consumption of sound energy.
(3) Beautify the landscape and enrich the outline of buildings.
Ecological garden is an effective exploration and application to beautify the urban landscape, increase the artistic effect of urban architecture, enrich the urban landscape, make the architecture "icing on the cake" and closely link the city with nature.
Application of Three Ecological Principles in Ecological Gardens
(A) adhere to the "ecological balance" as the leading factor, rational layout of the garden green space system.
Ecological balance is an important principle of ecology, which means that the ecosystem is in an extremely stable state. At this time, the structure and function of the system are adaptive and coordinated with each other, and the energy input and output are relatively balanced, so that the overall benefit of the system is the best. In the construction of ecological gardens, it is emphasized that the structure and layout of green space system should be coordinated with the natural topography, rivers and lakes, and the relationship with urban functional zoning, with an eye on the ecological environment of the whole city and reasonable layout, so that urban green space can not only surround the city, but also introduce nature into the city and maintain the ecological balance of the city. In recent years, many cities in China have begun to explore the combination of suburban and forest gardens, expand urban green space and take the road of ecological gardens, such as Beijing, Tianjin, Hefei, Nanjing and Shenzhen. 〔2〕
(2) Follow the principle of "niche" and do a good job in plant allocation.
The choice of urban garden plants actually depends on the allocation of niche, which is directly related to the aesthetic value of landscape and the comprehensive function of garden green space system. The concept of niche refers to the function of a species in the ecosystem and its position in time and space, which reflects the relationship between species and between species and environment.
In the construction of urban garden green space, we should fully consider the niche characteristics of species, reasonably select plant species, avoid direct competition among species, and form a multi-layer community structure with reasonable structure, sound functions and stable population, so as to facilitate the mutual supplement of species, make full use of environmental resources and form a beautiful landscape. Under the specific urban ecological environment conditions, the standards of plant selection should be anti-pollution, drought resistance, cold resistance, barren resistance, pest resistance and extensive management. For example, among the landscaping plants in Shanghai, Acer truncatum and Pinus massoniana have poor growth conditions and are not suitable for large-scale planting; Metasequoia glyptostroboides, Taxodium ascendens, Ligustrum lucidum, Magnolia grandiflora and palm have good adaptability and excellent growth, which can be used as the main types of greening.
In greening construction, we can use the differences of different species in space, time and nutritional niche to configure plants. For example, the Maple Leaf Gardens and Rhododendron Gardens in Hangzhou Botanical Garden are configured in this way. Acer truncatum is tall and upright, with deep roots and leafy leaves, and can absorb the upper layer of the community [