中文摘要：

采用PCR-DGGE技术,对‘寒富’苹果园生长季内土壤氨氧化细菌群落结构、多样性及其与土壤理化因子的相关性进行探讨。结果表明,不同时期土壤硝化强度、氨氧化细菌数量、种群组成及多样性表现出明显差异。其中,11月份土壤硝化强度最高,9月份最低,而氨氧化细菌数量则表现为11月份最低,7月最高。多样性特征分析表明,土壤氨氧化细菌多样性和均匀度指数均表现为11月份最高,9月份最低;而丰富度指数则表现为5月份与7月份最高,11月份最低;优势度指数则为9月份最高,5月份最低。系统发育分析结果表明,苹果园土壤氨氧化细菌均隶属于β-变形菌纲（β-Proteobacteria）,多为不可培养菌株,其中亚硝化螺旋菌属（Nitrosospira）为土壤优势菌属。氨氧化细菌与土壤理化性质相关性分析发现,土壤速效磷、速效钾含量与硝化强度、氨氧化细菌多样性指数、均匀度和优势度指数呈显著相关,而与土壤氨氧化细菌数量无明显相关性。说明环境因子时间分布的不均匀性是不同时期土壤氨氧化细菌群落结构组成差异的重要原因。

英文摘要：

Ammonia-oxidizing bacteria （AOB） are key organisms in soil nitrogen （N） cycle, and are considered as therate-limiting step of nitrification process. While it was not clear that whether environmental disturbances duringdifferent growth periods caused particular community structure of AOB and soil nitrification in apple orchard soil. Inthis study, PCR-DGGE method was used to investigate the community structure and diversity of soil AOB and theircorrelation with soil physical and chemical factors in apple orchard under four different growth periods of May（blossom period）, July （young shoot-growing period）, September （fruit-enlargement period）, and November （defoliation）.The results showed that soil nitrification activity, AOB counts, AOB community structure and diversity showedsignificant differences among different periods. Soil nitrification activity was the highest in November, but the lowest inSeptember. The AOB count was the lowest in November, but the highest in July. AOB shannon index and evennessindex were the highest in November and the lowest in September. Its richness index was the highest in May and Julyand the lowest in November. The highest and lowest values of dominance index were found, respectively, in Septemberand in May. All soil AOB belonged to the beta proteobacteria in apple orchard soil. And most of them were unculturedbacterial strain. Nitrosospira was the dominant genus in apple orchard. Soil available P and available K content hadobvious relationship with AOB nitrification activity, shannon index, evenness and dominance index, but no correlationwith AOB counts. All the results indicated that the distribution heterogeneity of environment factors in time was theimportant reason for the difference in community structure of soil AOB in different growth periods.