Study on the Effect of Reducing Haze by Urban Greening Trees

Although small in size, PM25 can do great harm to the environment, and city greening trees can reduce PM2.5 pollution to a certain extent. This paper reviewed the mechanism of city greening trees to reduce PM2.5 pollution, screening and classification of green land allocation model of PM2.5 reducing greening trees, and made prospect on how to construct the evaluation index system of PM2.5 re- ducing greening trees and urban green land allocation.

Foliar Dust Size Characteristics of Greening Trees in Aksu, Northwest China

Urban greening trees intercept the migration of atmospheric particulate matters near the ground, and it is difficult for the particulate matters trapped by foliage to re-elevate, thus reducing the hafm to humans. The dust-capturing ability and foliar dust size charactetistics of different greening trees are different In addition, the dust capturing of trees is distutbed by many factors such as sel natural and human factors. The foliar dust and natural dustfaJl in 11 common, tree species in Aksu, Northwest China were collected to analyze tihe particle size distribution diacacteristics,and obtain the concentrations of PM^ and PM10. The results showed that Pktanus acenfolia, Populus alba var. pyramidaJis and Uhnus densa. had high foliar dust attachment density and strong particle-capturing capacity,while Elaeagnus angustifoliaL., Pyrns sinldangensis, Sophora japonica L. had low foliar dust attachment density. The foliar PMZ5 and PM10 contents were highest in E. ongustifolia （0.68%） and Vitis vinefcra （3.59%）, tespectively. The volume fraction of fine partides was small in natural dustM and was kige in foliar dust The median of foliar dust particle size followed tiie descending ordei： industrial area 〉 transportation hub area 〉 residential area 〉 clean area; and the median of natural dustfall particle size followed the descending order： dear area 〉 transportation hub area 〉 industrial area 〉 residential area. There was a big difference between the two.

Absorption capacity of major urban afforestation species in north-eastern China to heavy metal pollutants in the atmosphere

Totally 24 arbor tree species and 6 shrub species were measured on their absorption capacities to heavy metal Pb, Cd, Cr, and Hg by collecting and analyzing the leaves of trees along different streets in Harbin city in Sept. to Oct. of 2003. The results showed that all the measured species had certain absorbency to the pollutants (Pb, Cd, Cr and Hg), but there existed significant difference in absorption capacity for different species to different pollutants. The measured tree species were classified into three categories by their absorption quantum of heavy metal pollutants. Among the species measured,Betula platyphylla, Ulmus pumila var.pendula, andPrunus persicaf.rubro-plena had high capacity in absorbing Pb;Populus xiahei, P. nigra var.Italica, P. alba x P. berolinensis andSalix matsudana had had high capacity in absorbing Cd;Phellodendron amurense, Syringa oblata, Salix matsudana, Pinus tabulaeformis var.mukdensis, Picea koraiensis, Prunus persica f.rubro-plena, P. triloba andAcer negundo, etc. had high capacity in absorption of Cr;Prunus triloba, Quercus mongolica, Salix matsudana, Sambucus williamsii, Pyrus ussuuriensis andSpiraea fritschiana were good at absorption of Hg. This study might offer scientific foundation for selection of urban afforestation species in different polluted conditions caused by heavy metals. Keywords Greening tree species - Heavy metal - Pollutants - Plumbum - Cadmium - Chromium - Mercury - Absorptivity CLC number S731.2 - X501 Document code A Foundation item: This study is financially supported by the Special Programme for Agriculture under Ministry of Chinese Science and Technology (No. 2002BA516A15-01).Biography: MU Li-qiang (1966-), female, Associate professor in Northeast Forestry University, Harbin 150040, P. R. China.Responsible editor: Zhu Hong

Fodder Value of Populus euramericana Green Biomass

The study of green mass nutritional value of the black poplars euramerican hybrids--Populus euramericana （Dode） Guinier was conducted. The content of fodder units, digestible and crude protein, crude fat, fiber, ash, nitrogen, calcium, phosphorus, carotene and others was studied. The study showed that the leaves had greater nutritional value than stems and branches. The fresh leaves collected from the annual shoots of trees were more nutritious than annual coppice shoots of reproductive plantations but after drying the nutritional value of the materials became similar. Indicators of stems nutritional value were similar to those of wheat straw and those of leaves that were close to the nutritional value of alfalfa. Nutritional value of leafy shoots was intermediate between that of stems and leaves. Young coppice plant material is much easier to harvest than that of mature trees. Minirotation cultivation of poplars allows obtaining significant reserves of both wood and leafing biomass in a short period of time per unit area. The ＂old clones＂ of euramerican hybrids of black poplars are more winter resistant than some southern poplars of Italian breeding. This allows cultivating them not only in places of habitual areas of poplars, but also in more Northern regions.

Priority placed on planting trees to extend green belts

Changsha-The central govern-ment is urging provincial officials toprotect and expand the green belts intheir areas. Local officials were urged to putthe"green drive"on the top of theiragendas by State Councillor ChenJunsheng,addressing a national con-ference on tree planting. Chen said at a conference that anaccountability system monitoringtheir performance would be intro-duced to ensure action on this"veryimportant task." Chen.speaking at the workingconference of National AfforestationCommittee.criticized some officialsfor their"over-enthusiasm in boost-ing the economy"by deforestingsome areas and turning them into"de-velopment zones."

A Green Leaf on the Big Tree

"WITH a dyed darkish-blue apron" was myself portrait when I first entered literarycircles. My hometown Chumen in Yuhuan is asmall town by the sea, a land of fish and ricein the southern reaches of the ChangjiangRiver. The gong and drum for the Liberationsounded in my childhood. I was infatuated bybooks then; the wing of ideas often entered mydreams like beautiful butterflies.