| Soil vegetation system is an important part of the ecosystem,and the restoration of its structure and function is an important sign of the recovery and health of the closed mine ecosystems.Exploring the resilience of soil-vegetation system and its synergistic tradeoff relationship is crucial for evaluating the stability and adaptive management of mine ecosystems.In this study,the Heidaigou open-pit mine dump in Jungeer Banner,Inner Mongolia Autonomousn Region was selected as the research area,and 5 typical vegetation restoration types(grassland,shrub,coniferous forest,broadleaf forest and mixed forest)were selected from the Yinwan Dump,West Dump,East Dump,and North Dump,which have been reclaimed for 8a,15 a,25a and 30 a,as the research object.Taking 1 group of natural forests and 1 group of uncultivated bare land as control,combined with field surveys and measured data,entropy weight method,correlation analysis method and spatio-temporal substitution method were used to reveal the evolution characteristics and tradeoff/synergy relationship of soil-vegetation system resilience under different vegetation restoration types.The main findings are as follows:(1)The physical,chemical,biological properties and vegetation community characteristics of the reclaimed soil in the openpit coal mine dump were significantly improved with the increase of reclamation years in the Loess Plateau.The mean value of soil physical properties of grassland and shrub was higher than that of coniferous forest,broadleaf forest and mixed forest at the initial stage of reclamation,but lower than that of tree forest with the increase of restoration time.Grassland coverage and species richness were always higher than those of other four types during the whole restoration process.Compared with other vegetation types,the improvement of soil chemical and biological properties of mixed forest was the most significant.In summary,the average values of all indexes in the soil-vegetation system of the five planted cover types improved gradually with the increase of reclamation years,but still did not reach the level of natural forest.(2)The resilience of the reclaimed soil-vegetation system in mining areas was evaluated from five dimensions: vegetation community succession,soil fertility,soil water conservation,soil carbon sequestration and soil biological activity.The recovery degree and rate of soil-vegetation system function were measured by entropy weight method.The results showed that the recovery degree of soil biological activity in grassland was higher than that in shrub,coniferous and broad-leaved forest with the increase of reclamation time.The soil carbon sequestration capacity and soil fertility of mixed forest broad-leaved forest and coniferous forest were better than those of grassland and shrub with the increase of reclamation years.Compared with other functions,the recovery of water conservation function was the worst,which only recovered to 60% of the natural forest at R30.The overall degree of soil system restoration under restoration was mixed forest > grassland > coniferous forest > broadleaved forest > shrub,and the overall degree of vegetation system restoration was mixed forest > broad-leaved forest > coniferous forest > grassland > shrub.(3)In general,the relationship between vegetation system and soil system resilience in grassland,shrub and broad-leaved forest was dominated by trade-off,while the relationship between coniferous and mixed forest was opposite.With the increase of reclamation years,there was a tradeoff relationship between soil and vegetation system.From R8 to R30,the tradeoff relationship between vegetation and soil system increased from 10% to 50%.In the process of vegetation restoration,the number and diversity of soil bacteria and fungi were the key factors affecting the restoration of vegetation system in grassland and shrub(P < 0.05).Soil p H,ammonium nitrogen,available phosphorus and organic matter were the key factors affecting the restoration of vegetation system in broadleaf forest,coniferous and mixed forest(P < 0.05).(4)Vegetation community succession,soil fertility,soil carbon sequestration,soil water conservation and biological activity were correlated with vegetation type and reclamation duration.In the future,ecological restoration in mining areas on the Loess Plateau should be divided into different vegetation types and management measure,so as to improve the structural and functional resilience and stability of soil-vegetation system,and eventually form a multilayer stability model combining “grass + shrub+tree”.At the same time,different artificial tending measures should be implemented for different types of vegetation restoration.Paying more attention to water conservation for grassland and mixed forest,fertilizer conservation for shrubs,and introduction of biological agents for broadleaf and coniferous forest,thereby promoting the synergistic development among various elements in soil-vegetation system restoration.Finally,it will improve the ecological resilience and speed of reclaimed mining areas,shorten the recovery period,and enhance the self-sustaining ability of soil-vegetation system in mining areas on the Loess Plateau.This thesis has 38 figures,7 tables and 185 references. |
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