关键词: 弯花黄芪, 镰荚黄芪, 根瘤固氮酶活性, 根瘤固氮潜力, 根瘤重量, 土壤因子

Abstract: Legumes are abundant in nitrogen-deficient temperate desert ecosystems and are important pioneer species in this desert region,providing a center of available nitrogen to other plant species coexisted in the vegetation. In this study,the root nodules of Astragalus flexus and Astragalus arpilobus,which are widely distributed in the Gurbantunggut Desert,were selected and sampled four times during their growth season to study the changes of the nodule nitrogenase activity (NNA),nitrogen-fixing Potential nodules (NNFP),weight of nodules (WON) and the relationships of two Astragalus species with the soil factors in different growing periods. The results showed that (1) the NNA,NNFP,and WON of both species were significantly different (P<0.05) in different growth phases,and reached the highest values in early June. In early May,electrical conductivity (EC) and total phosphorus (TP) were the main promoting factors for NNA and NNFP of Astragalus flexus,respectively,while soil organic matter (SOM) was the main limiting factor for NNFP of both species and for WON of Astragalus flexus. In late May,total nitrogen (TN) was the main limiting factor for NNFP of Astragalus arpilobus;The soil organic carbon (SOC) was the main limiting factor for NNA of Astragalus arpilobus in early June and the total nitrogen (TN) for NNA of Astragalus arpilobus in late June. The results of this study may provide an implications for the exploring the Astragalus plants for efficient symbiotic nitrogen fixation,as well as for the enhancement of symbiotic nitrogen fixation through the regulation of soil factors in the arid zone of Xinjiang.

Key words: Astragalus flexus, Astragalus arpilobus, Nodule nitrogen activity, Nodule nitrogen fixation potential, Weight of nodules, Soil factor