Assessment Of Ecological Performance At The Early Stage Of Spontaneous Vegetation Recovery On Coal Waste Pile

At present, in the field of the performance of ecological restoration, the long-term, systemic studis about dynamic monitoring and action mechanism of the relationship between environment and vegetation still are insufficient in our country. The scientific, systemic, practical index system and evaluation criterion of mining ecological restoration are not established. By investigating the fixed monitoring sample area, the thesis analyzed the basic characteristics of vegetation communities and soil physical-chemistry properties at different rehabilitation stage. According to the stage of ecological restoration and AHP-FCE model, this study established the assessment technology and method of ecological performance on coal waste pile at the early stage of spontaneous vegetation recovery, monitoring, contrasting and distinguishing the changes of eco-efficiency. Then the structure of the vegetation was summarized, which was suitable to Sima coal, Luan coal and Changzhi city. The practical monitoring and evaluation criterions of the restoration effects of the mining wasteland were put forward, and applied, systemic technology of eco-efficiency assessment was also developed, which set an example and palied an important radiation role in promoting the scientific implementation, management and evaluation of mining ecological restoration. The main conclusions as follows:1) During the early stage of spontaneous vegetation recovery on coal waste pile, the number of the family, genus and species of each community remained fluctuation; Cirsium setosum, Artemisia scoparia, Setaria viridis, Medicago sativa already adapted to the environment of the community; The proportion of species belonging to Compositae of the total was dominant, bud the species dominance was replaced by species belonging to Gramineae, with the increase of the convalescence, the main position of species of Compositae maybe appear again; The characteristics of growth and decline of the species in the fifth year of convalescence is most similar to natural secondary community. The index of growth and decline of the species was able to objectively, quantitatively describe the degree of stability of the biodiversity, the more tend to be 1.0, the greater stability of the species diversity, and maintaining between 2.690-2.741, the index of species richness keeping 1, the index of species evenness holding 0.931, the change of the value of tne community similarity also remaining between 0.688-0.710, but there was no significant linear relationship between the both index of growth and decline of the species and the community stability.2) With the increase of recovery, the index of community biomass were extremely significant differences (P<0.01) during the period of one to five years of the restoration; The biomass of herb with different vegetative form and its contribution to the total community biomass were basically similar in two years of convalescence, from that on, the biomass of the annual herb and its contribution to the total biomass showed a decreased trend; The allocation of the biomass of community in the fifth year, Puccinellia distans, Leymus chinensis and Medicago sativa, achieved to the configuration of natural secondary community still needed the longer time; The aboveground or underground biomass of Artemisia lavandulaefolia, Puccinellia distans, Setaria viridis, Medicago sativa, Melilotus officinalis, and total biomass maintained significant or extremely significant positive correlation, there also was an obvious linear regression relationship; The relationship of biomass and important value was not the same between different species, just as it between different biomass index of the same species and its important value; Increasing the coverage of the community, conduced to the accumulation of Puccinellia distans’underground biomass and Leymus chinensis’aboveground biomass, but harmful to the growth of underground part of Melilotus officinalis.3) Early ecological restoration on the coal gangue field, soil water content, soil density basically trended to decrease, but the soil total porosity changed another trend;The soil field capacity showed a trend of rise after the first reduce; Soil organic matter maintained fluctuation; Soil total organic carbon, readily oxidation organic carbon and its proportion of total organic carbon led to rise basically, the change rule of the particulate organic carbon was not obvious, but its contribution to total organic carbon reduced gradually; The pH maintained the range of 8.03 ～8.50, weakly alkaline, reducing year by year; In the second year, Total nitrogen, available phosphorus and available potassium decreased, but since then, they trended to rise basically. In addition, according to correlation analysis, them were found that, total nitrogen and pH value were very significantly negative correlation (P<0.01), available potassium and pH value were significantly negative correlation (P<0.05), available phosphorus and available potassiumwere very significantly positive correlation (P<0.01).4) Early ecological restoration, the index of growth and decline of the species and soil total porosity were significantly negative correlation (P< 0.05), and particulate organic carbon accounting for the proportion of total organic carbon were significantly positive correlation (P<0.05);The consumption of soil moisture was larger during the early growth of Populus tomentosa, its root and litter palied important roles in improving soil density, total porosity, increasing total organic carbon and readily oxidation organic carbon; Lower average moisture content, better gas porosity and permeability, rich total organic carbon, available phosphorus and available potassium were conducive to the biomass accumulation of Leymus chinensis, Setaria viridis. Increasing soil organic matter, particles organic carbon, available phosphorus and available potassium caused an adverse effect on the biomass accumulation of Artemisia lavandulaefolia, Melilotus officinalis.5) Compared with the first year of recovery, the basic characteristics of community, soil physical properties, soil chemical properties and the comprehensive ecological performance reached the "optimal" level in the fifith year at the early stage of natural vegetation recovery on the coal gangue field. In a word, in a long enough period, under the condition of artificial planting tree layer, the natural restoration of herb can realize the vegetation reconstruction in mining area.6) Based on the AHP-FCE evaluation model, taking the first year of recovery as a benchmark, ecological performance level setting by the recovery degree in each convalescence, this paper assessed ecological performance at the early stage of spontaneous vegetation recovery on coal waste pile. The evaluation results were objective and scientific, the evaluation technology were operable and practical. Which avoided the blindness that selecting natural secondary community as the ecological restoration goal, but uncertainty about whether it was the best recovery effect, and provided a new ideas for the ecological performance evaluation.