Influence Of Highway Construction On Fragile Ecosystems And Relevant Protection In The Saline-alkali Soil Region Of The Yellow River Alluvial Silt Plain

Saline-alkali soil is widely distributed in the Yellow River alluvial silt plain of north and northwest Shandong province. Saline-alkali soil problems in Dongying and Binzhou city, which lie in the center of Yellow River Delta, are prominent. In saline-alkali soil region, formidable natural conditions and man's activity make the structure of ecological systems simple, the stability of ecological systems weak. The ecological systems are subtle to outside disturbance. So they are fragile ecological systems.Study the cause of vulnerable ecological systems, and analyze their fragile characteristics. The assessment index system of ecological environment is established. It includes five aspects of land utilization type, vegetation coverage, soil qualification, water resources, and climate. The AHP method is employed to determine index's weight. The fragile level is assessed by the mode of Ecological Fragile Index (abbreviated as EFI). Take the three county of Wudi, Zhanhua, and Yangxin in Binzhou City as examples. It is obtained that their EFI values are 0.34, 0.53, 0.20 respectively. In corresponding, the ecological environment fragile levels are medium, severe and slight respectively. Ecological fragile level reflects the difference of natural, social and economic conditions. The more fragile the ecological is, the lower the natural, social and economic conditions are.In the saline-alkali soil region of Yellow River alluvial silt plain, highway engineering construction will severely impact the fragile environment of a range of 300m away from the highway. Highway network causes habitat segregation, which resulted in the reduction of biologic diversity. Engineering constructions damage the vegetation where a highway passes. During construction, bare soil of subgrade and soil-borrowing site is subtle to soil erosion in the heavy raining or big windy season. This decreases the soil organic content, which further worsens soil conditions, and increases the difficulty of vegetation growth after project completion. So it is to restore the damaged vegetation only by man-aided measures. Highway construction may cut off the water flow in the zone of high level ground water, and impact the hydrological geology. All those will initiate unfavorable effect to fragile ecological systems.Study the influence characteristics of highway construction on fragile ecosystems. Establish the assessment index system of influence level for ecosystem along the highway. Employ the impact degree index CI to analyze the impact level, and to analyze the ecosystem's quality. Take the Binzhou-Dezhou expressway as example; assess the fragile level of ecosystems in a range of 300m away from the highway, which include farmland, forest, orchard, saline-alkali barren land, river and depression of water ecosystems. The influence degree of construction of Binzhou-Dezhou highway on five ecosystems is: saline-alkali barren land ecosystem > forest ecosystem >river and depression of water ecosystem >orchard ecosystem > farmland ecosystem. Though the ratio of saline-alkali barren land occupied by the highway engineering is low, the impact of the highway project on the ecosystem is the most, in that the fragile level of this kind of ecosystem is the highest.Based on the fragile ecological environment characteristics and highway construction impact characteristics of saline-alkali region on Yellow River alluvial silt plain, associated with a project example, ecological environment protection measures are put forward, such as land resources protection, soil and water loss control, existing water system protection, primary vegetation protection et al. It is proposed that the barren soil may be covered by crop stalks or plastic membrane to decrease water evaporation. The greening vegetation suited for highway side slopes, median strip, and virescence zone along the two sides of highway is put forward. The trial technique of micro-irrigation is suggested to irrigate virescence vegetation. But the soil saline-alkali characteristics with water should be dealt with firstly.