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利用Dobereiner低氮培养基通过平板稀释法从四川核桃主产区的根际土壤中分离筛选高效固氮细菌,采用形态学、生理生化和分子生物学鉴定到种,并研究其生物量与土壤养分之间的关系,再通过Shannom-Wiener指数、丰富度指数、Pielou指数和Simpson指数对其多样性进行评价。结果显示,初筛固氮细菌89株,乙炔还原法测定其固氮酶活性复筛后,得到具有较好固氮能力的菌株25株,属于9个属,假单胞菌属和固氮菌属为优势。土壤养分与固氮细菌生物量的相关性表明,除与土壤有机质呈极显著正相关、与有效N呈显著正相关外,与其余指标均无相关性。在多样性研究中,巴中南江和宜宾兴文两地的固氮细菌种群丰富,其多样性和丰富度指数均较大。土壤养分与固氮细菌多样性的相关性表明,多样性指数、丰富度指数与土壤有机质分别呈极显著、显著正相关,与全N呈显著正相关,与有效N呈极显著正相关;均匀度指数与有效N呈显著正相关。
High-efficiency nitrogen fixing bacteria were isolated and screened from the rhizosphere soil in the main producing areas of Sichuan walnut by plate dilution method using Dobereiner low nitrogen medium. The species were identified by morphology, physiology, biochemistry and molecular biology, and their biomass and soil nutrient Then the Shannom-Wiener index, richness index, Pielou index and Simpson index were used to evaluate their diversity. The results showed that 89 strains of nitrogen-fixing bacteria were initially screened and acetylene reduction method was used to determine the activity of nitrogenase. After screening, 25 strains with better nitrogen-fixing ability were obtained, belonging to 9 genera, Pseudomonas and Azotobacter. The correlation between soil nutrients and nitrogen-fixing bacterial biomass showed no significant correlation with soil organic matter except significant positive correlation with available N and significant positive correlation with available N. In diversity studies, the nitrogen-fixing bacteria populations in Bazhong Nanjiang and Yibin Xingwen are abundant, and their diversity and richness index are large. The correlation between soil nutrients and nitrogen-fixing bacteria diversity showed that diversity index, richness index and soil organic matter were extremely significant, significant positive correlation, significant positive correlation with total N and significant positive correlation with available N, evenness Index and effective N was significantly positively correlated.