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北方大型露天矿区土壤有机碳库扰动与恢复研究

Study on disturbance and restoration of soil organic carbon pool in large-scale open-pit mining areas in Northern China

  • 摘要: 大规模露天煤矿开采严重扰动了矿区地形地貌和土壤碳循环过程。露天矿区土壤有机碳恢复提升符合“双碳”目标,对土壤肥力改善和生态系统自维持具有重要意义。为揭示露天采矿引起的土壤有机碳库的损失扰动特征,掌握矿区土壤有机碳恢复的影响因素及其提升策略,以我国最大的露天煤矿群准格尔矿区为研究区域,通过哨兵二号遥感影像提取了采损区域,采用了149个土壤采样和统计插值、影响因素回归分析等方法。研究结果表明,半干旱地区露天矿排土场矿山土与自然土壤的理化性质、生物活性等都具有明显差异,缺少自然表土覆盖的新复垦排土场矿山土有机碳含量极低,平均为0.19%;由于自然表土剥离不规范,无序混排等,据测算该区域表层土壤有机碳损失累计超过62万t;回归分析表明影响矿山土有机碳的恢复的因素依次是全氮(0.559)、复垦年限(0.225)和植被NDVI(0.172);调查表明复合植被恢复模式的土壤有机碳含量显著高于单一植被恢复模式,其中沙棘、苜蓿、草木樨构成的草灌群落土壤有机碳含量接近自然土壤。在单一植被恢复模式下,土壤有机碳含量恢复表现为:以沙柳等为主的灌木>以油松等为主的乔木>以火炬树等为主的小乔木>以紫花苜蓿等为主的草本植物。排土场复垦区平台和边坡土壤有机碳含量随时间变化不断增加,复垦年限5年后矿山土有机碳快速提升。排土场矿山土有机碳的持续提升是排土场生态修复成功的关键;控蚀保肥、添料增碳、植被汇碳、保护性耕作等措施是露天矿区排土场矿山土有机碳提升的主要技术途径。

     

    Abstract: The large-scale open-pit coal mining has seriously disturbed the landform and soil carbon cycling process of the mining areas. Restoration and improvement of soil organic carbon in open-pit mining areas is in line with the “dual carbon” goal, and is of great significance for improving soil fertility and self-sustaining ecosystems. To reveal the disturbance characteristics of soil organic carbon pool loss caused by open-pit mining, and grasp the influencing factors and improvement strategies of soil organic carbon recovery in mining areas, the Zhungeer mining area, largest open-pit coal mine group in China, was selected as the research area in this study. Sentinel 2 was used to extract the remote sensing images of the damaged area, and 149 soil samples were collected, as well as methods such as statistical interpolation and regression analysis of influencing factors were also adopted. The results indicated that there were significant differences in the physicochemical characteristics, and biological activity between the open-pit mine waste dump soil and natural soil in semi-arid areas. The soil organic carbon content of the newly reclaimed waste dump lacking natural topsoil coverage was extremely low, with an average of 0.19%. Due to non-standard natural topsoil stripping and disorderly mixed discharge, it was estimated that the cumulative loss of organic carbon in the surface soil of this area exceeded 620,000 tons. Regression analysis result showed that total nitrogen (0.559), reclamation period (0.225), and vegetation NDVI (0.172) were the positive factors affecting the recovery of mining soil organic carbon . The survey result also showed that the soil organic carbon content of the composite vegetation restoration model was significantly higher than that of the single vegetation restoration model, while the soil organic carbon content of the grass shrub community composed of sea-buckthorn, alfalfa, and sweet clover was close to the value of natural soil. Under the single vegetation restoration model, the restoration of soil organic carbon content was manifested as follows: shrubs mainly composed of Salix psammophila > trees mainly composed of Pinus tabulaeformis > small trees mainly composed of Rhus typhina > herbaceous plants mainly composed of Medicago sativa. The organic carbon content of the platform and slope soil in the reclamation area of the waste dump increased with escalation of reclamation years. After 5 years of reclamation, the organic carbon content of mining soil exhibited a rapid promotion. The continuous scientific improvement of soil organic carbon is the key to the successful ecological restoration of mining waste dump. Measures such as controlling erosion and fertilizer, adding materials to increase carbon, vegetation carbon sequestration, conservation tillage are the main technical ways to enhance the organic carbon content of mining soil in open-pit mining areas.

     

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