采煤矿区复垦土壤微生物固碳的驱动因素及其固碳潜力提升的研究

Increasing soil organic carbon accumulation is one of the key measures to improve soil fertility and quality and to restore soil ecosystems in coal-mining areas. At present, studies on sources of soil organic carbon in mining areas are mostly concerned with plants’ carbon sequestration, but the role of CO2-fixing microorganisms and their CO2-fixing potential in reclaimed soil in mining areas is still unclear hitherto. To address this scientific issue, the current project is worked out to carry out research on soil microbial CO2-fixing potential and driving factors based on the long-term reclamation field trial at the coal-mining subsidence area of Lu'an Group in Shanxi Province. The 13CO2-based laboratory culturing experiment, qPCR (quantitative polymerase chain reaction) technique and high-throughput sequencing were performed to 1) investigate the variation of biomass and community composition of soil CO2-fixing microbes in a chronosequence of reclaimed coal-mining field, 2) analyze the microbial CO2-fixing potential and driving factors of the chronosquence reclaimed soils, 3) explore the efficient fertilization practice to promote the succession of soil CO2-fixing microbial community along reclamation chronosequence and their CO2-fixing potential. Our research project aims to reveal the succession pattern of CO2-fixing microbial community and the driving factors of their CO2-fixing potential, and find an efficient fertilization practice in promoting microbial CO2-fixing potential in reclaimed coal-mining areas. It is expected to provide a theoretical basis for the fertility promotion of reclaimed soils with a novel perspective based on CO2-fixing microorganisms.

增加土壤有机碳累积是提升煤矿区土壤肥力和质量、恢复矿区生态系统的关键措施之一。目前针对矿区土壤有机碳来源的研究大都关注植物固碳，而固碳微生物类群及其固碳潜力对采煤矿区复垦土壤碳累积的贡献尚不清楚。针对这一科学问题，本项目依托山西潞安集团煤矿长期定位复垦试验，开展土壤微生物固碳潜力及其驱动因素的研究。采用基于13CO2的室内培养、荧光定量PCR和高通量测序等手段分析不同复垦年限矿区土壤固碳微生物的生物量和群落组成变化；探究不同复垦年限土壤微生物的固碳潜力及其驱动因素；探索如何通过施肥促进土壤固碳微生物的演替并提高其固碳潜力。本项目旨在揭示采煤矿区复垦土壤固碳微生物群落的演替规律及其固碳潜力的驱动因素，并探究出能高效提升采煤矿区复垦土壤微生物固碳潜力的施肥模式。以期从固碳微生物这一新的视角为促进矿区复垦土壤肥力提升提供理论依据。

固碳微生物可以潜在提高土壤肥力。然而，在采煤塌陷复垦土壤中，固碳微生物的潜力和功能在很大程度上尚未探究。因此，1)本项目首先采集了UL(未复垦)、CK(不施肥)、NPK(单施化肥)、M(单施有机肥)、MNPK(有机肥化肥配施)复垦一年的典型采煤沉陷地复垦土壤。采用定量PCR、酶联免疫吸附试验(ELISA)和高通量测序技术，探究复垦与施肥对表层土壤固碳微生物生物量、RubisCO活性和群落组成的影响。结果表明，复垦后固碳微生物优势类群(Proteobacteria、Cyanobacteria、Devosia和Marichromatium)显著改变(P <0.05)。施肥后固碳微生物群落组成显著改变。此外，M显著提高 RubisCO 活性，cbbL/16S rRNA 比值和cbbL基因丰度(P <0.05)，MNPK显著提高固碳微生物多样性、均匀度和丰富度(P<0.05)。土壤固碳微生物群落结构的显著影响因子为含水量、过氧化氢酶、可溶性有机碳和总磷。上述环境因子可以通过直接影响固碳微生物生物量、多样性和群落结构而间接影响土壤有机碳量。2)其次选取典型煤矿塌陷区复垦8年的玉米连作C_CK(不施肥)、C_NPK(化肥)、C_M(有机肥)、C_MNPK(化肥有机肥配施)；玉米-大豆轮作R_CK、R_NPK、R_M、R_MNPK，8个处理的0 ~ 20 cm表土进行研究。综合利用测定RubisCO酶活性、荧光定量 PCR和高通量测序等技术手段，研究轮作与施肥对复垦土壤固碳微生物的生物量和群落结构的影响。结果表明，土壤中的优势菌门为Proteobacteria、Actinobacteria和Cyanobacteria，聚类热图分析表明，除M外，连作下各处理的菌属相对丰度均高于轮作模式。无论连作还是轮作M和MNPK处理均显著提高了TN、TP、AK、PHO以及EOC值(P<0.05)。与其他处理相比，R_NPK显著提高了RubisCO酶活性，R_M显著提高了cbbL基因丰度(P<0.05) 。冗余度分析(RDA)表明， SM、TN和cbbL、TP和EOC对土壤固碳微生物的生物量、多样性和群落结构影响较大。综上，本研究表明，即使短期(1年)复垦和施肥也能显著影响固碳微生物群落结构，促进土壤碳积累。就施肥模式而言，有机肥(M和MNPK)施肥处理更有利于固碳微生物改善采煤矿区复垦土壤肥力；