秸秆还田配施化肥对砂姜黑土固碳细菌的影响

Effects of straw returning combination to fertility on the CO_2-assimilating bacterial community in the lime concretion black soil

农田生态系统是陆地生态系统中最活跃且固碳潜力最大的碳库之一,其中,细菌在农田生态系统生物固碳过程中发挥着重要作用。采用PCR-克隆测序技术、末端限制性酶切长度多态性分析技术（T-RFLP）及荧光定量PCR技术研究了不施肥（CK）,施氮磷钾肥（CK-F）,单独秸秆还田（W-NF）和施氮磷钾加秸秆还田（W-F）4种施肥管理对砂姜黑土固碳细菌群落结构、多样性及丰度的影响。结果表明,秸秆还田土壤的固碳细菌主要包括Nitrosomonas,Mesorhizobium和Bradyrhizobium等。在CK和W-NF处理中,土壤固碳细菌以严格自养菌为主,优势种群为亚硝化单胞菌属（Nitrosomonas）,相对丰度分别为73.2%和72.4%。在CK-F和W-F处理中,土壤固碳细菌中严格自养菌相对丰度减小,而兼性自养菌相对丰度大幅增加。其中,CK-F的优势种群为亚硝化单胞菌属（Nitrosomonas）和中慢生根瘤菌属（Mesorhizobium）,相对丰度分别为33.3%和17.6%。W-F的优势种群为亚硝化单胞菌属（Nitrosomonas）和慢生根瘤菌属（Bradyrhizobium）,相对丰度分别为26.4%和24.5%。施用化肥及秸秆还田均显著提高了土壤固碳细菌群落的多样性,其中化肥的影响大于秸秆还田。主成分结果显示施肥对土壤固碳细菌群落结构的影响大于秸秆还田。4个处理土壤固碳功能基因（cbb L）丰度为1.32×107~3.29×107拷贝·g-1（干土）,施肥及秸秆还田均能显著提高土壤细菌cbb L基因丰度,其中秸秆还田配施化肥的cbb L基因丰度最大。上述结果表明了施肥及秸秆还田对土壤固碳细菌群落结构,多样性及数量均有显著的影响。

Farmland ecosystem is the most active and one of the terrestrial ecosystem carbon pools. It has a big carbon sequestration potential, in which bacteria play a major role in microbial CO2 fixation processes. In this study, the composition and diversity of CO2-assimilating bacteria were investigated using cloning and sequencing, terminal restriction fragment length polymorphism（T-RFLP） and quantitative PCR. Soil samples were collected from the lime concretion black soil in Mengcheng, Anhui province with four treatments： CK（control, no fertilizer）, CK-F（mineral NPK fertilizers alone）, W-NF（wheat straw residue incorporation, no mineral NPK fertilizers）, and W-F（mineral NPK fertilizers combined with wheat straw residue）. The carbon fixation microorganisms mainly include Nitrosomonas, Mesorhizobium, and Bradyrhizobium, etc. In the treatment of CK and W-NF, the cbb L-containing bacterial communities were dominated by obligate autotrophic bacteria such as Nitrosomonas, Nitrobacter and Nitrosococcus. While in the treatment of CK-F and W-F, the obligate autotrophic bacteria decreased sharply and the facultative autotrophic bacteria increased sharply. In CK and W-NF treated soil, the dominant cbb L-containing bacterium was Nitrosomonas, and the relative abundances were 73.2% in CK and 72.4% in W-NF. In CK-F treated soil, the dominant cbb L-containing bacteria were Nitrosomonas and Mesorhizobium, and their relative abundances were 33.3% and 17.6%, respectively. In W-F treated soil, the dominant cbb L-containing bacteria were Nitrosomonas and Bradyrhizobium, and their relative abundances were 26.4% and 24.5%, respectively. Fertilization and straw incorporation both increased the diversity of cbb L-containing bacterial communities. Fertilization had a stronger effect on soil bacterial diversity and structure than straw incorporation. Fertilization or straw incorporation both increased bacterial cbb L abundance（1.32×107-3.29×107 copies·g-1 soil） with the highest cbb L copy number（3.29×107 copies·g-1 soil） in the W-F treated soil. All above results indicated that fertilization and straw incorporation significantly influenced the CO2 fixation bacterial community structure as well as increased bacterial abundance and diversity.