[Root Activities of Re-Vegetated Plant Species Regulate Soil Nutrients and Bacterial Diversity in the Riparian Zone of the Three Gorges Reservoir]

Plants modify the soil microenvironment through root exudation. It is important to study the dynamic changes of soil ecosystem from the perspective of root-soil-microbe interactions after vegetation restoration in the riparian zone of the Three Gorges Reservoir (TGR). The rhizosphere and bulk soils of Cynodon dactylon, Hemarthria altissima, Taxodium distichum, and Salix matsudana were collected from the vegetation restoration demonstration base of Ruxi River to explore the differences in nutrient contents and enzyme activities between the rhizosphere and bulk soils. At the same time, the diversity of the bacterial community in the rhizosphere and bulk soils was also investigated using the high throughput sequencing method, with the aim to clarify the growth adaptabilities and nutritional utilization strategies within a more precise rhizosphere range. The results showed that ① Suitable plants enhanced the transformation efficiency of rhizosphere nutrients in different ways to improve their adaptability to the soil environment in the TGR. Compared with bulk soil, root activities had significant effects on nutrient contents in the rhizosphere. Among them, SOC, AN, TN, and AP were enriched significantly to a certain degree, while the changes of potassium were not consistent in different plant species. ② In the process of vegetation restoration, the deposition of litter and root secretion indirectly regulated soil enzyme activity. Invertase, urease, and acid phosphatase, all exhibited positive rhizosphere effects (R/S>1) in these four suitable plant species. However, considering the differences in root structure and physiological characteristics between herbaceous and woody plants, the rhizosphere effect of these three enzymes in four plants was different. ③ The results of high-throughput sequencing showed that there was no significant difference in bacterial community diversity between the rhizosphere and bulk soil of four suitable plant species in the TGR. In addition, Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, Bacteroidetes, Planctomycetes, Cyanobacteria, Firmicutes, Nitrospirae, Gemmatimonadetes, WS3, and Crenarchaeota were the twelve most abundant bacterial phyla in the rhizosphere and bulk soils, serving the ecological functions of nutrition absorption and disease suppression. Their colonization was found to be beneficial to the stress resistance of plants growing in harsh riparian ecosystems in the TGR.

Keywords: Three Gorges Reservoir; diversity of soil bacterial community; riparian zone; soil enzyme activity; soil nutrients; suitable plant species.