Dynamics of arbuscular mycorrhizal fungi distributions, soil nutrients and enzyme activities in rhizosphere soil at different growth stages of Angelica sinensis

Abstract:

[Objective] In order to understand the relationships between arbuscular mycorrhizal fungi (AMF) and soil nutrients and soil enzyme activities in Angelica sinensis field, the AMF spore densities, soil nutrient and soil enzyme activities of rhizosphere soil were investigated at its different growing stages. The results will provide a theoretical basis for the application of AMF in A. sinensis production. [Methods] Rhizosphere soil samples were taken at different growing stages of A. sinensis. The rhizosphere soil nutrients, soil enzyme activities, AMF spore densities, and glomalin were measured and the correlative analysis and principal component analysis (PCA) were also conducted based on the measurements for further understanding the dynamic metabolism. [Results] With the completion of the A. sinensis growth period, the AMF spore density of its rhizosphere soil decreased at early growth stages and then increased continuously in the following growth stages. And the easy extractable glomalin (EEG) and total glomalin (TG) had significant positive correlation with soil organic matter, total nitrogen, acid and neutral phosphatase activities (P<0.01), and the contents of EEG and TG in rhizosphere soil were significantly increased with A. sinensis growth (P<0.05). Soil organic matter and total nitrogen also show an increasing trend with A. sinensis growth. The available phosphorus content remained constant during the early growth stages, decreased significantly at the middle stage and gradually increased at the later stage, while the available potassium content increased significantly at the first and middle growth stages and decreased at late growth stages. Acidity and neutral phosphatase activities of rhizosphere soil increased gradually, while urease activity increased at the early growth stage, and decreased significantly in the middle and later stages. pH value fluctuated during different growth stages of A. sinensis. The correlation analysis shows that AMF spore density is significantly positively correlated with acid phosphatase activity, while the acid phosphatase activity significantly positively correlated with total nitrogen, organic matter, EEG and TG in rhizosphere soil, but significantly negative correlation between available phosphorus and available potassium, indicating that AMF could affect rhizosphere soil nutrients and enzyme activities. The correlative analysis refracts the relationships among the indexes. In particular, the PCA shows that the A. sinensis growth stage is the main factor for affecting the physical and chemical indexes of rhizosphere soil. [Conclusion] The AMF spore densities at the rhizosphere of A. sinensis mainly reflect the ability of AMF to secrete glomalin and its contribution to the storage of carbon and nitrogen in rhizosphere soil, and the glomalin also affects the soil enzyme activities and nutrients metabolic cycle, and plays an important role in improving the soil quality and promoting the growth of A. sinensis.