Studies On The Mechanisms And Optimized Model Of Ecological Restoration In Coal Gangue Waste Land

Coal,a non-recyclable energy,plays an important part in the economic development of the nation.However,during the course of mining,washing and processing,great amount of coal gangue is produced and accumulated into coal gangue wasteland.This wasteland is a typical badly-damaged ecosystem,occupying precious soil resources,causing pollution to the atmosphere,water and soil,leading to ecosystem degeneration and biodiversity loss,and ultimately damages the ecological security of the coal-mining area.Therefore,enhancing the ecological restoration and reconstruction in the coal gangue wasteland has great practical significance and future implication prospective in improving the ecological environment and achieving ecosystem health and ecosystem sustainability of the coal-mining area.This research is conducted in the coal-gangue wastelands in Jixi and Hegang Mine,major coal production bases in Northeast Heilongjiang.Sufficient statistics and data are collected through field investigation and monitoring,fixed point observation,field experiment, laboratory experiment and relative index investigation and analysis.The following are the four major subjects of this research:(1) research on the natural state background value of coal gangue wasting land;(2) research on the plant species choice of ecological restoration in coal gangue wasting land;(3) research on the matrix improvement of coal gangue wasting land;(4) research on the ecological restoration patterns of coal gangue wasting land.Results are as follows.1.Due to the influence of the loss of seed bank and the limitation of extreme natural condition upon the coal gangue wasting land in northeast Heilongjiang,the rate and degree of natural restoration of vegetation is comparatively much lower than those in other parts of the country.Hence,the task of ecological restoration is of greater difficulties.2.Natural vegetation restoration condition is rather bad in the 10-15 year coal gangue wasting land in Jixi and Hegang Mine.There is only a few annual and biennial herbs on the surface soil,the vegetation coverage lower than 17.5%,and biomass being 26.07 g/m.The constitution of vegetation community is simple as only having four families,four genera,eight species,with compositae being the major species.Water shortage in the matrix is extreme and moisture content of the surface efflorescene is 4.19%.Nutrient shortage and imbalance are also rather serious-extreme shortage in total N,total P,available N,and available P while sufficient amount of total K and available K.Heavy metal pollution is slight in the area with Hg being the main polluting heavy metal elements.Hence,shortage of normal soil structure, extreme worsening of water condition and extreme shortage of nutrient in the gangue hill areas are the limiting factors. 3.Siberian elm,Japanese red pine,and Mongolian scots pine manage to survive and grow normally in the gangue hill.The two-year survival rate of these specie reaches 100%,80.44% and 73.35%,making them excellent Arbor Species selection for vegetation restoration of gangue hills.The two-year Amorpha Fruticosa L achieves at 99.7%of survival rate,having 65.9cm of plant height,65.5cm of crown width,and 33.4g of biomass for individual plant,thus becomes the initial shrub plant for gangue hill vegetation restoration.Excellent herb plants include sweet clover and Parthenocissus Quinquefolia.Lespedeza Bicolor Turcz and Alfalfa are not suitable for plantation in gangue hill areas.4.Tailrace dredging soil and coal ash are solid waste elements used as additives.Their proper co-application with gangue in the matrix improvement works effectively in improving soil texture,considerably strengthening water storage capacity and water-holding capacity of the gangue base,lowering PH value of gangue base,and improving the condition of nutrient loss.Besides,the application scientifically adjusts the nutrient balance of gangue base and effectively controls heavy metal pollution,therefore promote the growth of plants.5.The Scots pine + Red pine- + Sea buckthorn model,pure Sea buckthorn forest model and pure Larch allelopathy forest model are the excellent restoration models chosen for the gangue field.The Arbor,shrub,herb and liana plants restoration model of Siberian elm, Japanese red pine or Mongolian Scots pine + Amorpha fruticosa L + Sweet clover + Parthenocissus quinquefolia can adjust to the site conditions of gangue hills effectively,and rapidly cover the surface soil,efficiently prevent the soil and water loss.This model is the excellent restoration model chosen for the gangue hill.6.The soil and water loss caused by loosing structure of gangue hill surface soil greatly influences the vegetation growth living at the bottom slope of gangue hill,and leads to a lower survival rate.Therefore,the vegetation restoration of gangue hills had better carry out at the middle and top of slope first.Further vegetation restoration project at the bottom of slope will be more effective when carried out after the initiative restoration of plantation efforts and the primary control of water and soil loss at the middle and top of slopes.