Abstract:

The restoration of ecosystems in damaged alpine coal mining areas is a global problem. It is important to ensure the stability of ecosystems in mining areas by optimizing restoration measures. In this study， three sowing methods were implemented， namely： i） revegetation by sowing four gramineous species （Elymus breviaristatus， Poa crymophila， Poa pratensis， Festuca sinensis； gramineous grasslands， designated H）， ii） sowing three Fabaceae species （Medicago ruthenica， Melilotus officinalis， Medicago sativa； leguminous grassland， designated B）， and iii） sowing four Poaceae and three Fabaceae species （gramineous and leguminous grasslands， designated HB）. Additionally， utilizing different proportions of sheep manure and slag soil， four fertilization levels were implemented， namely （sheep manure ： slag soil） heavy fertilization （1∶5， F₁）， medium fertilization （1∶8， F₂）， light fertilization （1∶11， F₃）， and no fertilization （F₄）. Hence， 12 different restoration treatments were generated by factorial combination of these three sowing and four fertilizing methods. The variation in herbage growth and soil properties under the different restoration treatments was evaluated and compared over a number of years. The ecosystem health evaluation was quantitatively judged by using the grassland ecosystem health assessment model OCVOR. The results showed that vegetation cover and aboveground biomass were optimized by the mixed sowing of Poaceae and Fabaceae under the heavy and medium fertilization levels （HBF₁， HBF₂） and increased with time from establishment. Levels of soil organic carbon， available nitrogen， available phosphorus， and available potassium were all substantially higher on the restoration plots after two years of restoration than after one year， but after three years had declined again to levels similar to those measured after one year. In the third year of restoration， the levels of soil organic carbon and available nitrogen were progressively increased （P<0.05） with increased fertilization level， while the law of changes in available phosphorus and available potassium were not significant. The OCVOR index of gramineous grassland under the heavy， medium， and light fertilization （HF₁， HF₂， HF₃）， and also of the leguminous grassland under the heavy fertilization （BF₁） increased significantly （P<0.05） with the years of restoration. Additionally， the OCVOR index of gramineous and leguminous grassland increased significantly under the heavy， medium and light fertilization （HBF₁， HBF₂， HBF₃） （P<0.01） over time. Except for the treatment BF₁， the ecosystem health status and recovery under the treatments HF₁， HF₂， HF₃， HBF₁， HBF₂ and HBF₃ were determined to be unhealthy. Corresponding to these evaluation results， the OCVOR index under the same six treatments increased by 28.61%， 33.03%， 11.46%， 38.96%， 33.79% and 9.83%， respectively， after 3 years of restoration， compared to the first year of restoration. Moreover， the biggest increases were seen under the HBF₁ treatment. Overall， the treatment comprising mixed sowing of Poaceae and Fabaceae under the heavy fertilization level （HBF₁） was found to be most conducive to the health and stability of the ecosystem in the Muli mining area.

Key words: high cold mining areas, artificial grassland, ecosystem, health evaluation