离子型稀土矿迹地生物炭改善豆科植物固氮微生物群落结构的研究

Ionic rare earth mine is specific in Southern China, because of extreme lack of carbon, nitrogen and other nutrients, the abandoned land is difficult to be covered by vegetation naturally. The preliminary study of our team shows that the combination of biochar and leguminous plants has a good restoration effect, furthermore, the success of the plant in situ restoration depends on the benign interaction between the plant and the microorganism. Presumably, biochar improve the community structure of root and endophytic nitrogen-fixing microorganisms, and therefore promote the growth and the ability of soil improvement of legumes plants. In order to verify this hypothesis, Canavalia ensiformis and soybean as experimental material, the effects of different proportions of biochar on community structure of root and endophytic nitrogen-fixing microorganisms were tested at different growth stages, using high throughput sequencing of nifH gene and fluorescence quantitative PCR (qPCR) and other experimental techniques, the regulation mechanism of biochar on the growth of leguminous plants was analyzed, predict, isolate and verify the core nitrogen-fixing microorganisms preliminarily. Through the implementation of this project, not only the mechanism of microbial regulation of biochar to improve the survival rate and the ability of soil amelioration of leguminous plants could be expounded, but also provide support for making better use of rhizobium-legume symbiotic nitrogen fixation system to improve the soil amelioration effect and the theory of ecological restoration in the abandoned land of ionic rare earth mine, provide reference and enlightenment for other biochar improvement systems.

我国南方特有的离子型稀土矿采矿迹地因碳、氮等营养元素极度缺乏导致植被难以自然恢复，课题组前期研究表明，施加生物炭配合种植豆科植物具有较好的修复效果。植物原位修复的成功取决于植物与微生物之间的良性相互作用，因此推测生物炭改善了豆科植物根际和内生固氮微生物的群落结构，从而促进了豆科植物的生长及土壤改良能力。为验证此假设，本项目以优良豆科改良植物剑豆和主要豆科作物大豆为试验材料，采用nifH基因高通量测序和荧光定量PCR等分子生物学技术，研究不同比例生物炭施加对豆科植物不同生育期根际和内生固氮微生物群落结构的影响，并初步预测、分离和验证核心固氮微生物类群。通过本项目的实施，不仅可以明确离子型稀土矿迹地生物炭提高豆科植物存活率和土壤改良能力的固氮微生物调控机制，还可为充分利用根瘤菌-豆科植物共生固氮体系提高离子型稀土矿迹地土壤改良效果、完善生态修复理论提供支持，为其它生物炭改良体系提供借鉴和启示。

我国南方特有的离子型稀土矿采矿迹地因碳、氮等营养元素极度缺乏导致植被难以自然恢复，课题组前期研究表明，施加生物炭配合种植豆科植物具有较好的修复效果，推测与生物炭改善了豆科植物根际微生物的群落结构有关，但具体机理尚未明确。因此，本项目组以豆科改良植物剑豆和主要豆科作物大豆为植物材料进行研究，探析生物炭改良的机理。一是对来源于不同国家的剑豆种质资源进行评价，并分析各类型种质的特色及可能用途；二是通过两轮筛选，分析剑豆和大豆不同种质对离子型稀土矿迹地原矿土的耐受性，筛选出剑豆高耐受性种质3份和低耐受性种质2份；三是采用基因高通量测序技术分析，发现不同比例生物炭添加对大豆和剑豆根际微生物群落结构具有较为明显的影响，初步筛选出主要固氮微生物类群；四是通过剑豆根系分泌物广泛靶向代谢物组分析发现，生物炭的添加显著提升了剑豆根系黄酮、酚酸类、核苷酸及其衍生物等代谢物，进而影响剑豆的存活率及土壤改良能力。通过本项目的实施，初步明确离子型稀土矿迹地生物炭提高豆科植物存活率和土壤改良能力的微生物调控机制，为充分利用根瘤菌-豆科植物共生固氮体系提高离子型稀土矿迹地土壤改良效果、完善生态修复理论提供支持，为其它生物炭改良体系提供借鉴和启示。