Investigation On Vegatation Recovery Of Distured Soil Of Freeways In Guanzhong Plain

With the booming development of road construction, especially the freeway's construction is greatly contributed to the rapid development of regional economy. However, it also brings environmental degradation which could not be ignored. Otherwise the theory of road slope vegetation restoration reseach and practice lagged seriously behind the road construction, and restricted the slope revegetation. Also, the previous studies lack of vegetation recovery during the operating road did not focus it. Thus, to the disturbed land projects, the slope vegetation restoration can be particularly important.In this paper, by the way of combining field investigation and laboratory analysis methods, we applied the method of space instead of time and chose the research object: freeway embankment slope, cutting slope, overpass area. Corresponding the above, 14, 5, 6 plots were selected respectively, which was based on the different vegetation restoration periods and different aspect, including 1, 3, 6, 9, 16, 17, 19 a in Guanzhong plain. And we set 2 control plots (40 a) in embankment slopes. Meanwhile, we investigated the plant resources of the 25 plots in detail, analyzed soil physical and chemical properties,vegetation composition and diversity under the different recovery periods, and obtained the artificial vegetation that were fit for the study area. Also, the limiting factors of revegetation were given. The results obtained were described as follows:(1) Soil chemical and physical properties of 3 kinds of plots changed with the soil layer, and the surface (0-10 cm) structure, fertility were better than the subsurface (10-20 cm). By contrast with the Loess plateau nutrient classification, the soil nutrient of embankment slope kept at the higher level. Contrast with the control plot, soil fertility of embankment slope peaked at the 17th year. The soil fertility of overpass area also was at a high level. But that of cutting slopes showed low level. Then, the key of plant restoration in the study area was the cutting slope.Fractal dimension of water stable aggregates was significantly negatively correlated with organic matter, total nitrogen. Thus it could be applied to characterize the level of soil fertility. It took obvious correlation with other soil chemical and physical properties also, which showed that it could be used in the disturbed soil, just like the road project.(2) 98 species appeared in the 3 kinds of plots, including 11 artificial species and 92 natural species. By analyzing the various ecological indicators of artificial vegetation, the results showed that Oxalis corymbosa DC. and Trifolium repens L. these two plants were not suitable for planting in the freeway slopes which were absent of human management and protection in Guanzhong plain. On the contrary, Coronilla varia L., Zoysia japonica Steud. and Medicago sativa L. were proved to be excellent artificial species for restoration in the road slopes.(3) The 92 natural species were mainly made up of gramineae, compositae, leguminosae and rosaceae. And through the analysis that the natural plants'settlement time, the quantity and type of life changed over time came to the trend of vegetation succession: annual herbâ†'annual or perennial herbâ†'perennial herbageâ†'perennial herbage and small shrub community.(4) The results of analyzing the diversity within community(α-diversity) indicated that the diversity of embankment slope communities reached the peak at 6 a,17 a respectively. In addition, the second was higher than the first. The results of diversity among communities demonstrated that species change was always along the direction of natural succession and communities with big differences were often in the late stage of succession.(5) By analyzing the relationship between theα-diversity with factors such as soil, time, the results showed that it was the time, organic matter, total nitrogen, inorganic nitrogen which were the factors that affected the vegetation recovery in the disturbed soil. Furthermore, the human factor was an unavoidable factor that had dual effects.