A Study on the Ecological Environment Protection Technologies Applied in Highway Construction in Desertification Areas
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【Author in Chinese】 陈爱侠；
【Author's Information】 长安大学， 交通运输规划与管理， 2010， 博士
【Abstract】 Recently high-grade highway construction has obtained rapid developments all over the world. The highway construction has promoted flow of population, economic, material, giving rise to regional economic benefits on a societal level. Meanwhile, building highways would obviously pose a negative impact on the environment, especially in desertification areas, because of the fragile ecological environment; Moreover high-grade highway construction would do nothing but make that situation worse and cause an irreversible harm to ecological environment of desertification areas.Based on the Inner Mongolia Inter-province highways—SangGenDaLai-GongZhuGeng Highway (simplified as "Sang Gong Highway"below) and ShangDu-AnYe Highway(simplified as "Shang An" Highway), this essay analyzes on the influencing mechanisms of highway construction on the ecological environment in desertification areas, puts forward the ecological environment protection technologies applied in highway construction in those areas, summarizes the feedbacks brought by certain technologies and facilitates environmental sustainable developments as well as the highway construction in desertification areas.Relying on the impacts of vegetation coverage shifts and sand surface moisture changes on sediment transport rate before and after highway construction and the reasons why construction spoil and fill sands causes dune activation, this essay explores the mutual interaction mechanisms of ecological factors such as sand hazards to highway and sand movements which have lend the evidence to the fundamental experiments and technical innovations to prevent and control sands. By investigating and evaluating the attributes of sand particles and fluid in wind-blown sand areas, this essay discusses environmental disturbing mechanisms highway construction has brought to wind-blown vulnerable ecological zones. By analyzing influences of the disturbance by highway construction to surface vegetation, sand flow and the changes of sand nutrients on vegetation transpiration, this essay further to unveil the reasons why it is difficult for desertification farm and pastoral areas to recover the perturbations of highway construction in itself.In terms of environmental characteristics that Sang Gong Highway runs through HunShanDaKe sandy land and Shang An Highway goes across desertification farming and pastoral areas, the desertification-area ecological environment protection techniques are put forward—low-standing sand barriers should be installed at a place of 30m away from both sides of desert-crossing highway subgrade or in the highway spoil and fill areas; High-standing sand barriers should be installed in the drifting areas where lie in the distance of 50-80m upwind and 40-50m downwind of desert-crossing highways subgrades. For large-area drifting sand regions, the combined sand barriers which combine low-standing with high-standing barriers should be installed. For highway embankments seriously corroded by wind in farming and pastoral areas, certain remedial measures such as covering slopes with gravel or gravel soil should be taken. With species-combination experiments being considered synthetically, different combinations are proposed to restore and rehabilitate road-region ecology of desertification areas, for example, Caragana Korshinskii is one kind of advantage species to prevent wind and stabilize sands along the sand-crossing highways; Artemisia desertorum and Salix gordejevii are both shrubs, two kinds of superior shrubs that can stabilize sands rapidly; C. microphylla which can serve as the primary dominant species in the desertification farming and pastoral areas, along with Leymus chinensis. Artemisia frigidal, Agropyron cristatum,. Agropyron mongolicum, Medicago sativa and other herbaceous plants integrate into shrub-grass group and such group may achieve dimensional ecological restoration.By using field-testing measures, the effects if certain ecological environment technologies are applied in highway construction in the desertification areas are evaluated and analyzed. Test results indicate, after installing low-standing sand barriers along sand-crossing roads, ground roughness has raised to 5.64cm and surface wind-break potency to 63.1%, high-standing sand barriers have made surface wind-break potency reach 58.5% and the maximized wind-break potency is up to 74.8% if combined barriers are installed; The soil environment of low-standing and high-standing barriers has obviously improved, which manifest itself in the decreased soil bulk density, the increased soil porosity, the moistures and higher soil nutrient content compared to shifting sandy land. Establishing desertification area road-region ecological project has supplied better soil microecology environment to the growth of road-region wild plants. The field survey unveils that wild vegetation species in Sang Gong highway area has multiplied and perennial stable wild sand fixing plants have reached 2-4 plants/m2, mainly including Agriophyllum squarrosum,Polygonum divaricatum and A. desertorum Vegetation coverage has increased from 5% to 15%, which favors the stability of road-region ecosystem.With certain ecological environment protection techniques being applied along Sang Gong highway, highway sand calamity is being radically eliminated. It is estimated that the economic benefits will amount to approximately (?)252 million. The annual costs for road maintenance would decrease by 35% after such ecological remedial measures are to be taken in Shang An highway subgrade slope. All in all, the application of such ecological environment protection technologies in desertification areas has brought about both environmental and economic benefits.