Study On Vegetation And Soil Characteristics Of Landfill Sites In Shanghai

With the development and expand of cities all over the world, the environmental impact of landfill and vegetation reestablishment had became a very urgent and obvious environmental issues. Landfill was a common way to deal with urban rubbish in most countries all over the world. As landfill occupied large land area, caused very serious soil contaminated, and also leaded to many of other environmental problems, research of greening and vegetation reestablishment in closed landfill sites had the vital significance.Including Minhang Sports Park and Zhenguang Park which were both remodeled closed landfill sites, we investigated the vegetation in 11 landfill sites in 7 districts in shanghai and sampled the soil samples in each landfill sites. In order to research greening and vegetation reestablishment in closed landfill sites, we analyzed species composition, community structure and plant diversity of the vegetation community to find which plants species suitable for closed landfill sites remodeling. Moreover, we tested physical and chemical characters of soils and quantities of heavy metals in soil samples, and analyzed relationship between the vegetation and soils in landfill sites to provide scientific evidences for virescence rebuilding in landfill sites. The results showed that:1.)The plant community was conducted and 189 plant species which belonged to 165genera and 77families were detected. There were 13 evergreen trees,32 deciduous trees,12 evergreen shrubs,12 deciduous shrubs,58 annual herbaceous,45 perennial herbaceous and 11 vines, respectively, accounting for 6.9%,17%,9.5%,6.3%,31%,45% and 5.8%. Herbaceous species took 55% in all plant species. Trees and shrubs are mainly artificial vegetation.172 Shanghai native species were found in this survey which belonged to 29 families, accounting for 90% in all plant species.17 Alien species were found, accounting for 10%. The number of native species(29) was not obviously more than the number of alien species on the level of family, which accounted for 38% in all 77 families. The situation of the landfill site vegetation showed that:Shanghai native species took a relatively higher proportion in the vegetation in landfill sites which might represent the native species have stronger adaptability. Natural recovery trees were mainly deciduous trees as Broussonetia papyrifera, Celtis sinensis, Morus alba and Melia azedarach. Solidago Canadensis was the dominant herb species, which might shows that alien invasive species were in the ascendant in the vegetation reestablishment and could create nice soil conditions for other plants.2.) By compering the community structure of vegetation at different Closure time landfill sites, the changes progesing of vegetation is:-Solidago canadensis, and other native herbs first to survive at this condition, and with the soil condition have improved, shallow-rooted tree of native trees began to grow, and gradually associated with hackberry, mulberry, Neem, at present, the natural forest vegetation dominated by deciduous broad-leaved forest; but in a kind of place where there seeding source, also can find some seedings of privet, camphor, palm and other species.3.) Soil bulk density at different sampling points is similarly, but the Jade Mountain landfill Minhang maximum density up to 1.47 Kg/m3, more than 1.35 Kg/m3 (Shanghai local standard) and it is the main factor to limit plant growth.Changes in Soil aeration porosity at different sites have a range of 1.19-2.98%._In addition to the Republican Village, landfill soil is acidic, the other sites have a alkaline soil Soil EC valuein at the Minhang and other three locations is less than 0.1ms/cm, it shous that soil nutrient are deficiency, the metal (As,Cd and Zn) value are more than three national environmental quality standards,the highest content of As is up to 518mg/kg and is 10.75 times the standard national levels.4.) Suggest1:It is a consideration to conversion the landfill sites with the strong human disturbance and development pressureconsider to an open green space, and building landscape of native plants which is growth in Shanghai.And to select this native plants as the main tree species, to avoid select the introduction of the new superior garden Green plants.Suggest 2:It is a good idea to construct a dense vegetation covering"forest islands"in some sites where there a plenty of natural plants.such as the Hongkou District Zhabei District Republican Village Liangcheng. If we can enhance protection this high mountain of garbage, this special sites can as a special type of city forest which have an important role in produce a habitat for animals and reduce the urban heat island effect.