园林树木学西农吉文丽第二章1英语.ppt

Chapter 2 Function of woody landscape plants in urban greening ( 3 hours)Two parts: 1  Environment protection  2 Greening and beautifying environment        Environmental protection function of woody landscape plantsuImproving environment(改善环境作用)Ø Adjusting temperature(调节温度)Ø Increasing relative humid (提高湿度)Ø Air purification （吸收二氧化碳、放出氧气；吸收有毒气体阻滞烟尘；排放杀菌素）Ø LightØ Noise preventionuProtecting environment （保护环境作用)ØWater-reserving, water and soil conservation (涵养水源、保持水土)Øwind prevention and sand fixation (防风固沙)ØFire and disaster prevention (防火、抗灾)Characteristics of urban environment  lLight： the radiant intensity of light in urban and visibility is low because of a great of dust。

lTemperature：：a great of heat coming from factories, power stations and cars makes air temperature high.lMoisture：：Relative humid in urban environment is low because the water drain away from the drainage system ,although a great of Cloud Condensation Nuclei and heavy precipitation exist in urban area.lAir：：air pollution heavy, O2 low，CO2 highlNoise pollution：：heavyThe effect on adjusting temperature 调节温度调节温度 Comparison of the effect on adjusting temperature among common street trees ( according to Wu Yi’s study in 1963，unit ℃）Species T in full light T in shade △T银 杏 40.2 35.3 4.9刺 槐 40.0 35.5 4.5枫 杨 40.4 36.0 4.4悬铃木 40.0 35.7 4.3白 榆 41.3 37.2 4.1合 欢 40.5 36.6 3.9加 杨 39.4 35.8 3.6臭 椿 40.3 36.8 3.5小叶杨 40.3 36.8 3.5构 树 40.4 37.0 3.4楝 树 40.2 36.8 3.4梧 桐 41.1 37.9 3.2旱 柳 38.2 35.4 2.8中 槐 40.3 37.7 2.6垂 柳 37.9 35.6 2.3  The bigger difference of temperature between canopy and atmosphere (∆T) will be, the better effect of shading will be.The shading effect is proportional to shading quality and range. The shading quality means crown density, leaves area and opaque.[ [遮遮荫荫效效果果与与树树种种“荫荫质质”即即树树冠冠密密、、叶叶面面大而不透明的荫质优）优劣、荫幅大小成正比大而不透明的荫质优）优劣、荫幅大小成正比] ]The reasons of tree decrease temperature: reflect 20-25% of sunlight;absorb 30% of sunlight ;some of heat is absorbed by water transpirationThe decreased temperature is different between single tree and patch forest. Patch forest low the temperature not only under the tree, but also the temperature outside. Warming effect In winter, trees can increase the temperature around trees because the trees have many branches and trunk where more area access to the sunlight than an open space. To sum up, trees have the function of decreased T in summer and increased T in winter. Of cause, decreased T in summer is more important than increased T in winter.Water aspectlwater purificationlIncreasing relative humid        It is most important for trees to improve the air humidity. For example, a mature Eucalyptus species get 4000kg water from soil to meet its growth.95% of the water released into the atmosphere by transpiration. The humidity there may be 20 times higher as compare to the open space, even higher than the same area of water苏联科学家移伊万诺夫在莫斯科地区，在17℃的条件下所测定的各树木蒸腾速率结果(g/kg.h)如下：   松树152  忍冬252   白蜡326  桦木341    榆树344  栎树364  扬树369  美国槭388   椴树390 苹果 530lReducing water table wetland--transpiration Air purificationO2 release CO2 absorptionthe chemical composition of earth’s atmosphere is as follows:Nitrogen(N2):78%;Oxygen(O2):21%;CarbonDioxide(CO2):0.03%;Plus other miscellaneous gases, including H2O. Urban areaCO2↗02↘, CO2 500-700ppm.When CO2 is 500ppm, people will fell uncomfortable; When CO2 is 2000-6000ppm, headache, high blood pressure, vomiting; When CO2 is at 10%, people will die.Plants are the regulator of CO2 and O2In photosynthesis, a plant can produce 32g O2 by absorbing 44g CO2. The plant breathes at the same time, only use 1/20 O2 it released.Broad-leave forest per hectare everyday absorbs 1000kg CO2 and releases 730kg O2 An adult as the weight of 75kg will need 0.75kg O2 and release 0.9kg CO2 everyday.So one person need 10 m2 forest or 50m2 turf grass or 30-40m2 greening land. By the year 2010, China's urban green area will achieve more than 35 %, green coverage has reached 40% and above, public green area per capita reached more than 10 ㎡, the city center district public green area per capita reached more than 6 ㎡.        Actually, the photosynthesis of different trees is different. The CO2 absorption of broad-leave forest usually is higher than needle-leave forest.  Absorption of toxic gases Atmospheric pollution, including a wide range of toxic gases, mainly to SO2, followed by HF and CI2. Many woody landscape plants have the ability of toxic gases absorption.①SO①SO2 2: : Oxidation SO2 --------highly toxic Sulfite ion ---------- sulfate ion (30 times lower toxicity) SO2 absorption of different trees is different:垂柳、加杨、榆树、构树、刺槐、海桐、枸桔、厚壳树、女贞等。

The SO2 absorption of deciduous trees usually is higher than evergreen trees, even more needle-leave trees. ② ② HF：HF poisoning effect on the human body, 20 times more effective than sulfur dioxide on. Not few tree species have highly ability of HF absorption.柑橘类可以吸收较多的氟化物而不受害象泡桐、梧桐、大叶黄杨、紫薇、女贞、银桦、乌桕、蓝桉等也是抗HF的树种③ ③ CI2 吸收CI2能力较强而且抗性也强的树种有：悬铃木、泡桐、刺槐、女贞、银桦等，还有旱柳、臭椿、赤扬、水蜡、卫矛、忍冬也是净CI2的较好树种④ ④ P Pb b 悬铃木、石榴、刺槐、女贞、大叶黄杨等⑤ ⑤ HgHg 夹竹桃、棕榈、樱花、桑、大叶黄杨、八仙花等 Dust blockThe air in the urban area and the factories and mines, in addition to harmful gases, still contains a lot of dust. The dust often can lead to eyes, skin or respiratory disease. The air dust can be blocked by Trees’ branches and leaves, then washed away by rainwater.The ability of blocking dust of trees species is different. The trees with dense crown, rough foliage or furry foliage have high ability of blocking dust. E.g.构树、榆树、朴树、木槿、刺楸等。

Releasing SpinosadThe number of bacteria in downtown area is 7 times more than that in park area. One of the much less bacteria reasons is many plants released Spinosad ( or phytoncide). E.g. 桉桉树树、、肉肉桂桂、、柠柠檬檬,etc. can release aromatic oil which has the ability to kill bacteria. 黑核桃、桉类、悬铃木、紫薇、柑橘类, phytocide. 各类林地的减菌作用不一样，松树林、柏树林及樟树林减菌能力强，可能与它们的叶子能散发某些挥发性物质有关 Improving lightThe light is very different between park and street in summer.In the park, there are about 20-25% light of the leaf reflectance; 35-75 % light absorbed by the crown; 5-40% light projected through the forest canopy. Therefore there is low light in the park.Plant absorb light band is mainly red and orange light and blue-violet light, reflected light is green, so in terms of optical quality, forest and lawn have a large number of green wavelengths of light.This green light in park is much more comfortable than the light in the streets, squares, and is good for eyes. Especially, green light makes people feel comfortable , refreshing and quiet in summer.Reducing noiseNoise is a kind of environmental pollution. Urban dwellers always suffer from greater levels of noise pollution than other areas. If noise exceeded 70 decibels, it will be harmful to peopleThe noise always exceeded 70 decibels in downtown area, that is why prohibit car horn in many cities. Combination of tree and shrubs may reduce noise. According to a measurement in 1976, the results as follow:①12m wide Platanus acerifolia(悬铃木) can reduce over 3-5 decibels than an open space. ②20m wide mixture of street trees（e.g.雪松、杨树、珊瑚树、桂花 planted in a row, respectively）can reduce 5-7 decibels than an open space. ③A 30m wide Miscellaneous forest（以枫香为主，林下空虚）reduced 8-10 decibels than open space；18m wide forest belt of 圆柏、雪松（ Lush foliage, even from top to bottom）reduced 9 decibels;45m wide 悬铃木 young trees reduced 15 decibels.④ 4m wide hedge wall of dense foliage（由椤木、海桐各一行组成） reduced 6 decibels . Usually trees with low branch , dense crown, low crown, lush foliage have good noise reduction effects.树木分枝底、树冠低、叶多、多枝、树冠紧密者减噪音效果好。

树木分枝底、树冠低、叶多、多枝、树冠紧密者减噪音效果好  Good noise reduction trees:  乔乔木木类类----雪雪松松、、柏柏、、龙龙柏柏、、水水杉杉、、悬悬铃铃木木、、梧梧桐桐、、垂垂柳柳、、云云杉杉、、山山胡胡桃桃、、鹅鹅掌掌楸楸、、柏柏木木、、臭臭椿椿、、樟樟树树、、榕榕树树、、柳杉、栎树等柳杉、栎树等  小小乔乔木木及及灌灌木木----珊珊瑚瑚树树、、椤椤木木石石楠楠、、海海桐桐、、桂桂花花、、女女贞等 Soil erosion prevention When it rains, the crown can retain 15-40% rainfall. If it rains heavily, some rainfall will fall into the litter   Under heavy rain, rain fell on the litter layer, and the litter can absorb 5-10% rainfall, others  is slowly absorbed by soil.    If it is a large and intense rainfall, the soil cannot absorb all the rainfall. The remaining water under the layer may form runoff, and the water is clear, and did not take soil away. Different species have different interception rate. Generally, the trees with Lush foliage and rough foliage have high interception rate 。

Needle-leave tree ＞ broad-leave treeShade-tolerant tree species ＞ heliophilous speciesFor the purpose of water conservation ,we should select these trees with large dense crown, high crown density, high rainfall interception rate, high shade-tolerance, easily formed super absorbent litter. Deeper and wider root system is one of the choices.Deep roots is benefits for soil reinforcement and slope stabilization and also helpful for water infiltrating into deep soil (e.g. tree:柳、槭、胡桃、枫杨、水杉、云杉、冷杉、圆柏等乔木; shrub:榛、夹竹桃、胡枝子、紫穗槐; vine:紫藤、南蛇藤、葛藤、蛇葡萄) Windbreak and Sand-Fixation If windbreaks is wide, thick, it will be significant for the wind speed reduction.Shelterbelt planted in desert area reduced soil erosion and increased sand fixation. The effects of shelterbelt are related to species selected and manner planted.不同结构林带的防风效果不同结构林带的防风效果 水平位置范围平均风速%林带结构0—5 倍树高0—10倍树高0—15倍树高0—20倍树高0—25倍树高0—30倍树高紧密结构253747546065疏透结构263139465257通风结构493940444954疏透结构和通风结构的防护距离要比紧密结构的为大，减弱风速的效率也较好。

紧密结构的林带因形成不透风的墙，形成回流，所以防护范围反而小了The efficiency of windbreak is different varying with species. Selecting windbreak species:Rapid growth;High toughness of branchNot bend offDeeper and wider rootsStrong resistance to diseases and pestsLong lifeEconomic benefits华北地区常用杨、柳、榆、桑、白蜡、紫穗槐、桂香柳（沙枣）等在南方可用马尾松、黑松、圆柏、榉、乌桕、柳、台湾相思、木麻黄、假槟榔等Fire and disaster preventionFire-resistant tree Species generally contain more moisture and thick cork layer (e.g.苏铁、银杏、栎类、榕类、棕榈、女贞、珊瑚树、罗汉松、夹竹桃、黄菠萝etc.) They can prevent the spread of fire and reduce fire, but cannot extinguish fire. Other Protective effectsSnowbreak forest can protect roads, railway and residential area in windy and snowy area. Mangrove forest as wave prevention forest or shelterbelt planted on shallow mudflats in tropical marine areasTidal forest as tidal wave and salty wind prevention plant in the coastal areas. Many plants can monitor air pollution.。