In recent years, the night lighting market in domestic cities has been in full swing. The comprehensive construction of the night view of the tourist city brought about by the international large-scale conference is well-known. The urban night scenes brought by the important domestic commemorative activities have also achieved good results. The major provincial capital cities and famous cities have also improved the landscape lighting of key areas. . Looking at this momentum, urban lighting will have fruitful results everywhere before the completion of a well-off society in 2020. With the full coverage of the landscape lighting of urban buildings, roads, plazas and other densely populated areas, the city's parks, embankments, landscape belts and even the mountains are also filled with landscape lighting.
Therefore, the successful and undesigned landscape lighting of urban plants has affected and affected, and it has become a victim of nighttime ecological balance.
02 The role of urban vegetation and plant sleep
Urban vegetation refers to all plant species that cover the urban surface, including natural species and artificially cultivated species. It is the only primary producer in the urban ecosystem, forming the basics of the food chain, and the photosynthesis exercised is the original source of energy and organic matter in almost all ecosystems. It has important functions of self-purification, beautifying urban landscape, enriching urban architectural outlines, providing leisure and entertainment, and disaster prevention and shelter.
Botanists believe that plants also need to sleep. Initially, the most extensive theory explaining the sleep movement of plants was the "moonlight theory." Scientists who put forward this argument believe that the sleep movement of leaves can make plants suffer from moonlight as little as possible. Excessive moonlight exposure may interfere with the normal photoperiod sensory mechanisms of plants and impair plant adaptation to day and night changes. However, what puzzles people is why many tropical plants without photoperiod also have sleep movements, which cannot be explained by the “moonlight theory”.
Since the "moonlight theory" cannot explain, the problem of plant sleep is unresolved, but it is certain that plant sleep is real, but how long the time and cycle of sleep is to be further studied by botanists. Plants have formed an adaptability to the environment during the evolution process. The nighttime illumination is extended by about 3 hours per day, which breaks the plant's adaptability to the light in the light climate zone, causing disturbances in the physiological and biochemical indexes of the garden plants. Normal growth may even cause it to die.
Light quality is an important factor affecting the normal growth and development of plants. From the point of view of the light source, different light sources of artificial illumination at night emit different wavelengths of light and have different physiological effects on plants; from a plant perspective, the photomorphogenesis and photosynthesis of plants depend on certain wavelengths. That is to say, in addition to controlling photosynthesis as an energy source, light quality also acts as a trigger signal to affect plant growth. The color of the light that is not suitable for the wavelength causes the plant's life activities to be disordered, causing it to become sick or even die.
03 Current status and lighting methods of plant lighting
According to the tree light, it is a variety of lighting fixtures developed specifically for urban trees. Some are round, some are square, some are semi-circular with a curvature, and some are custom-made hoop shapes. But without exception, they are not installed next to the trunk at the bottom, or they are installed at the intersection of the trunk. The luminaire installed at the bottom avoids direct contact with the trees, but has a greater glare effect on pedestrians. Luminaires installed at the intersection of trunks, whether they are conventional or bionic or bird-shaped luminaires, require a hoop-mounted structure for fixing, which requires frequent adjustments based on the growth cycle of the trees, if neglected for maintenance and Management can cause catastrophic damage to trees. In reality, this kind of tragedy caused by poor maintenance in the later stages is not uncommon. In addition to tree lights, landscape lights, street lights, buried lights, high-beam spotlights, etc. can also have a direct or indirect impact on night plant sleep.
04 The impact of excessive plant lighting on the ecology and the harm it brings
Unreasonable lighting methods are harmful to urban vegetation. First, it affects the normal growth cycle of plants. Plants use sunlight for photosynthesis during the day, but they also need rest during the night. Changes in photoperiod play a key role in regulating plant seed germination, seedling elongation, cotyledon extension, and flowering control and dormancy. Plant leaves can predict seasonal changes by measuring the length of the night, which is also a signal that triggers the leaves and hibernation of the plants. The trees are exposed to strong light at night, causing dormancy to be disturbed, causing the morphological changes of the deciduous form and the formation of winter buds. If artificially irradiated, trees or shrubs will continue to grow in the fall when entering the frost season. The leaves will also contain chlorophyll, which will delay the defoliation period. At the same time, over-illuminated plants will dry and lack water to grow excessively, and because of chlorophyll Destruction, the plant will also show other undesirable symptoms such as lightening of the color. Of course, the dormancy of trees and the formation of winter buds, in addition to the role of light, are also related to nutrient climate, air pollution and maintenance management. Therefore, the different effects of light pollution on the growth of different types of plants have yet to be further studied.
Second, it affects the nighttime rest and activities of birds and insects. Studies have shown that except for a handful of animals that are active at night, most animals are quiet at night and do not like strong light. However, nighttime outdoor lighting, especially the skylights, spilllights, disturbing lights and reflected light produced by plant lighting often brighten the animal's living and rest environment, disrupting the rhythm of the animal's day and night biological clock, making it impossible for people to sleep and rest. For wild animals and fish animals, in addition to visible light effects, radiant energy emitted by lighting fixtures also has an impact on animal life and growth. For example, after an animal absorbs illumination radiation energy, it not only causes temperature changes, but also the electric field and physiology of animal cells. When the goldfish is placed in a magnetic field, the stronger the magnetic field strength, the more the fish do not want to eat the bait. Another example is the effect of nighttime illumination on pests. Due to the lightness of insects, outdoor nighttime lights can attract a large number of insects, especially in the spawning period. A large number of insects are concentrated in the illumination area, and the eggs will soon become larvae and adults. In turn, it causes pests. It is worth noting that for the beneficial insects and birds, the outdoor lighting that is too bright at night will kill many beneficial insects and beneficial birds directly to the light. For example, the neon lights in the Frankfurt amusement park in Germany will burn tens of thousands every night. Benefit insects. If a city, especially a city that never sleeps, has tens of thousands or even hundreds of thousands of outdoor lights, the ecological balance of the region will be seriously damaged. One of the reasons for the high number of mosquitoes in summer nights in Dusen, USA is related to the fact that thousands of neon lights in the city "killed" the beneficial birds and beneficial insects of numerous mosquitoes.
In summary, the lighting of plants has an irreconcilable contradiction between the animals and plants themselves and the ecosystem. However, plant lighting should not be completely negative, and proper and reasonable plant lighting is what our lighting practitioners are pursuing.
05 Ways to change the status quo
First, lighting designers should scientifically and rationally design the illumination lamps of plants, and put forward reasonable values for the wavelength, illumination and illumination time of the lamps. When setting up landscape plant lighting, you need to understand the relationship between the source spectrum and plant growth. First of all, the landscape reflectivity of different landscape plant landscapes is different because of the difference in surface materials and the angle of the exposed surface. Some studies have pointed out that the natural plant illumination spectrum curves are similar, and the nighttime color of the plants is closer to the natural state. It is more suitable for the night illumination source of garden plants, such as fluorescent lamps and LED light sources. When the spectrum is relatively discontinuous, the reflection spectrum is partially missing, which causes the garden plants to deviate from the natural state at night, or to make the plant color more biased towards the source color of the light source itself, such as high-pressure sodium lamps and metal halide lamps. Therefore, careful selection is required in the design of night scenes. Second, the spectrum is an inducing signal that affects plant growth and development, regulating plant photosynthesis. The high-pressure sodium lamp and metal halide lamp spectrum is a discontinuous spectrum, which provides limited effective energy for plant growth and has little effect on plant growth. The spectral energy distribution of white LED can provide blue light spectrum and a small amount of red light spectrum for plant growth. Greater impact.
Second, lighting technology engineers should combine the growth rules of trees with the installation method of tree lights to propose a more appropriate installation method, and strive to minimize the destructiveness of trees. For example, the way to combine landscape lighting with tree lighting
I.e. the ability to control light beam angle of the lamp, but also influence plant selected lighting fixture a major consideration. Generally, the appropriate beam angle should be selected according to the height, density, shape, etc. of the plant. According to the beam angle, the luminaire can be divided into three types: wide beam, medium beam and narrow beam. The wide beam is suitable for illumination that requires emphasis on the shape of the plant: for densely lit trees, using 40°-45° light control for better illumination; on the contrary, when it is necessary to illuminate a narrow For tall trees, it is best to choose a luminaire with a beam angle between 6° and 20°.
Third, the manufacturer not only to lighting improvement in style and appearance of the lamp according to the tree, but also to give different options according to the tree at a wavelength of light for different trees. If necessary, it is necessary to design and produce plant growth lamps that promote plant growth and development for different tree species according to the growth environment of the plants. A plant growth lamp is an artificial light source, usually an electric light source, intended to stimulate plant growth by emitting an electromagnetic spectrum suitable for photosynthesis. Plant lights are used in applications that do not have natural light or need to fill light. For example, in winter, when possible daylight hours may not be sufficient to achieve the desired plant growth, the lights are used to extend the time the plants receive light. If the plants don't get enough light, they will grow up. LED growth lamps vary depending on the application. It has been known from studies of photomorphogenesis that the green, red, far red and blue light spectra have an effect on root formation, plant growth and flowering, but there is not enough scientific research or field testing to recommend specific color ratios using LED growth lamps. It has been shown that many plants will grow normally if red and blue light are applied. However, many studies have shown that red and blue light provide only the most cost-effective growth method, and that plant growth is still better under light-supplemental green. LED growth lights should keep the plants at least 12 inches (30 cm) away from the plants to prevent leaf burns.
Fourth, the lighting construction unit should strengthen the regular maintenance of the tree lights to ensure that the growth and development of the trees are not affected or minimized by the lamps. Buried lights and projection lights are often used in green lighting, which is prone to glare. Therefore, if you do not use the buried and projected way to make trees, you must choose a luminaire with a grille or hood to reduce glare. The production. Special attention should also be paid to the choice of the position of the luminaire to ensure safety. The line should be hidden and cannot directly allow pedestrians, especially children, to come into contact with bare electrical parts. In places where buried lamps are used, it should be noted that the temperature of the surface of the light outlet should not be too high to avoid burning pedestrians. It is strictly forbidden to install the floodlights directly on the tree poles. Overweight lamps will adversely affect the growth of the trees, and the wires are wrapped around the trunks, which has the risk of electric leakage and hinders the daytime.
06 How to create a harmonious ecological night environment
Lighting designers should be particularly cautious in the choice of lighting colors for trees. White light can express the original color of the plant relatively purely naturally, making the outline of the plant more clear and clear, and the layering will also increase. Generally, the yellow light emitted by the high-pressure sodium lamp can increase the warmth of the environment, but it should not be used to illuminate the green plants, because it will make the surface of the green plants look gray and yellow, lacking vitality, and for the yellow plants that need to highlight the color. There will be better results. Red light and orange light make plants appear completely different from people's original impressions. They are more charming and smart, making the environment more warm and bright.
Urban night lighting has become an indispensable part of urban development. Existing urban lighting systems may not consider too much of its impact on landscape plants, so it is necessary to change the impact of urban night lighting on landscape plants. Or plant species is difficult to accomplish. It requires the planning department to incorporate the research into the design in the early stage of planning and design, and more professional and reasonable design for the lighting design practitioners. A beautiful city needs to be able to continue to play its role in night lighting, but also to reduce its impact on the growth and development of landscape plants themselves.
Nightlights are not a reproduction of the daytime landscape. Instead, they use light to reshape the nightscape, show the beautiful, neat landscape at night, and hide the disorderly, run-down landscape at night. Using light and shadow effects to combine plants and lighting reasonably organically, the night of the city around me becomes more beautiful, and the city's ecosystem becomes more harmonious.