| It is an urgent task for our country to rehabilitate the damaged ecosystem, in particular, the abandoned land reclamation of mining sites.Based on the land reclaimed during 1992-2005 period, the study evaluated the benefit of ecosystem rehabilitation effort through a serial of field survey, laboratory testing and comprehensive analysis in the reclaimed land system of the Hei-Dai-Gou Opencast Coal Mine in the Loess Plateau. Habitat changes in the relaimed lands were monitored through the surveys and analysis on vegetation composition, soil nutrient status and soil microorganism activities. The characteristics of the"vegetation-soil-microorganism ecosystem"on the reclaimed land were discussed and the eco-environmental benefits brought by the rehabilitation were evaluated.A vegetation survey was conducted in the relaimed ecosystem of the Hei-Dai-Gou Opencast coal mine. The results showed that a total of 115 species (subordinate to 24 families, 80 genuses) intruded into the reclaimed land within the 15 years from 1992 to 2005. In the vegetation annual plants played the dominant roles although the perennial plants had increase substantially in compared with the plant compositeon in the initial relaimation stage. Some perennials have been found among the most aboundent plants and may take about 40%-50% of the total plant species.Correlation analysis based on Grey System Theory was used in soil quality assessment. The results showed that soils in most reclaimed lands in the Hei-Dai-Gou opencast coal mine of the Loess Plateau were turning into the benign circulation categories of grade three or grade two. No grade one and grade five in the study areas were found. The order of quality evaluation from the best to the worst in terms of relaimation effectiveness was as follow: Hippophae rhamnoides+Glycyrrhiza uralensis>Populus simonii+Salix matsudana+Hippophae rhamnoides>Hippophae rhamnoides>Malus spp.+Prunus spp.>Caragana mirophylla>Calamagrostis epigejos>Leymus chinensis>Control(Original lands)>Medicago sativa>Prunus armeniaca+Medicago sativa>Populus alba var. pyramidalis (artificial)>Astragalus adsurgens>Populus simonii (Pristine)> Leymus sacalinus>Pinus tabulaeformis>Populus simonii + Hippophae rhamnoides> Control(Before reclaimation).On the basis of analysis for landscape features, such as landform, vegetation and soil property, the author took Hei-Dai-Gou opencast coal mine as an example and studied the landscape dynamic succession, landscape features and landscape types by means of the remote sensing (RS), geographical information system (GIS) and MAP-GIS and the theory of landscape ecology. The results showed that there were 6 landscape types at the mine, which could be divided into 323 patches by landform and slope gradient, surface material and topography; Most of the natural landscapes had disappeared,all ecosystem was unstable; Correlative buildings and mine accounted for 23.368% of the land area, artificial woodland and artificial pasture, which occupied largest proportion of the whole research areas (52.11km2), were 67.891%.After analyzing the landscape characteristics, the author used several methods to calculate ecosystem service value. The order from big to small in terms of the effect of soil hydraulic erosion control from the different vegetation compinations in the investigated areas was as follow: arboreal and bush mixed woodland (11731.364t/km2.a)>artificial pasture (11641.637t/km2.a)>bush land (11331.044t/km2.a) >woodland (11296.534t/km2.a)>abandond (9709.049t/km2.a).The environmental quality and the ecological effect from the biologic relaimation efforts were assessed based on the community composition, microorganism activety, landscape structure and soil nutrient status. The changing trends of the reclaimed ecosystem were also predicted based on the study results from the Hei Dai Gou opencast coal Mine in the Loess Plateau.
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