Abstract:

The Qinling region is rich in molybdenum (Mo) resources, and large-scale Mo mining has resulted in ecological issues. Increasing soil carbon storage may be a key measure for ecological restoration in mining areas. Assessing the contribution of native plants to soil carbon storage in mining areas may help to select a group of native vegetation species with good ecological recovery ability, which can accelerate the soil formation process and maintain soil fertility in mining areas. This study focused on different vegetation types in a naturally restored area of a molybdenum tailings pond in Qinling. By comparing the carbon content of surface and rhizosphere soils, the content of dissolved organic matter (DOM), the sources and types of DOM, the mineral phase composition of different rhizosphere soils, and the CO₂ respiration of the rhizosphere soils, a selection of native wild plant species with high soil organic carbon sequestration benefits was made. The results showed that plant carbon sequestration generally ranged from 100% to 650%, with Phragmites australis, Imperata cylindrica, Anaphalis sinica, and Miscanthus being the most effective in soil carbon sequestration in the mining area. From the perspective of DOM, the DOM mass fraction of surface soils of various vegetation types ranged from about 12.35 to 20.96 g∙kg⁻¹, and the DOM mass fraction of rhizosphere soils ranged from about 4.52 to 15.71 g∙kg⁻¹, generally about 3-12 times the DOM content of exposed areas. Phragmites australis was more conducive to generating high DOM content. Compared to other plants, the CO₂ respiration of the rhizosphere soils of Anaphalis sinica was higher, with the CO₂ content reaching 3.5 times that of air at a soil depth of 5 cm. The EEM results showed that DOM mainly originated from the decomposition of litter and root exudates, with a higher humus content in the surface soil of Phragmites australis, contributing more to soil humus. From the perspective of soil carbon sequestration in mining area restoration, this study suggests that Phragmites australis, Anaphalis sinica, Miscanthus, and Imperata cylindrica can serve as pioneer plants for ecological restoration in the ecologically fragile areas of the Qinling molybdenum tailings pond. They can help increase carbon sequestration in the ecologically fragile areas of the Qinling Molybdenum tailings pond, thereby achieving long-term goals of ecological carbon sequestration and restoration.

Key words: soil carbon content, carbon sequestration by plants, carbon sink in mining area, mining area restoration, plant selection

摘要：

秦岭地区钼矿资源丰富，大规模开发钼矿带来了生态环境问题。增加土壤碳储量或许是矿区生态恢复的关键措施，以此评估矿区本土植物对土壤储碳的贡献或有助于筛选出一批生态恢复能力好，能加速矿区成土过程和维持土壤肥力的本土植被物种。以秦岭某钼尾矿库自然恢复区不同植被为研究对象，通过比较不同植被群落表层和根际土的碳含量，溶解性有机质（DOM）含量，DOM的来源与类型，不同根际土壤的矿物物相组成情况，植被根际土壤CO₂呼吸量等，筛选出对土壤有机碳增汇效益高的本土野生植物种群。研究结果表明：植物碳增汇普遍在100%－650%之间，其中芦苇（Phragmites australis）、白茅（Imperata cylindrica）、香青（Anaphalis sinica）、芒草（Miscanthus）等植物对矿区土壤固碳的效果最为突出；从DOM角度看，各植被表层土DOM质量分数为12.35－20.96 g∙kg⁻¹，根际土DOM质量分数为4.52－15.71 g∙kg⁻¹，普遍为裸露区域DOM质量分数的3－12倍，其中芦苇更有利于产生高含量DOM；与其他植物相比，香青根际土壤CO₂呼吸量较高，土壤深度为5 cm时可达空气CO₂含量的3.5倍。三维荧光检测结果表明，DOM主要来自凋落物、根系分泌物分解等外源输入，其中芦苇表层土中腐殖质含量较高，对土壤腐殖质贡献更大。从矿区土壤恢复碳汇角度分析，认为芦苇、香青、芒草和白茅这几种植物可作为秦岭钼矿生态脆弱区生态恢复的先锋植物，其有助于提高秦岭钼尾矿库生态脆弱区碳汇，达成长效生态固碳和生态恢复协同目标。

关键词: 土壤碳含量, 植物固碳, 矿区碳增汇, 矿区恢复, 植物筛选