| Napahai wetland is located in the northwest of Yunnan province and the only low-latitude-high-altitude and seasonal semi-closed plateau wetland in China, which is also an important water source in upper reaches of the Yangtze River and plays a critical role in undertaking snow and ice melt water, conserving soil as well as controlling flood. In wetland ecosystem, the soil microobial community plays tremendous role in improving soil fertility, vegetation productivity and maintaining material circulation and transformation in biosphere. Therefore the biocenosis is an indispensable part for maintaining the ecological equilibrium. However, the composition and diversity of microbial community in Napahai Plateau wetland is still unknown.In this study, fluorescence quantitative PCR method was used to analyze the quantity and distribution of bacteria, fungi and archaea in the bogsoil (YN), swamp meadow soil (SD) and peat soil (NT) in the sampling areas of Napahai plateau wetland in dry and rainy season. It can be clearly concluded from the overall distribution of microorganisms in the soil that bacteria have the largest numbers followed by archaea and fungi have the smallest numbers. Moreover, the numbers of all kinds of microorganisms is higher in the rainy season than in the dry season. The transition of soil from YN to SD and NT sampling areas can be regarded as the native swamp soil, swamp meadow soil and meadow soil formed due to the degradation of Napahai wetland. Furthermore, the change of the numbers of bacteria and fungi in soil are colsely related to the soil degradation mechanism arising from anthropogenic disturbance:bacteria have the largest number in the SD sampling area, while fungi have the largest number in the NT sampling area. The correlation analysis between numbers of microorganisms and soil physico-chemical factors showed that, the number of bacteria and pH were significantly negatively correlated (p< 0.05); number of archaea and the concentration of element Mn and Fe were significantly positively correlated (p< 0.01); and the number of fungi and total potassium, available potassium and available phosphorus were significantly positively correlated (p< 0.01).In order to explore the diversity and composition of microbial community in Napahai plateau wetland, we analyzed the V4 region in 16S rRNA gene of bacterial and archaeal and ITS2 sequence of rRNA gene of fungi. The results showed that the diversity and relative abundance of bacteria, archaea and fungi community were higher in rainy season than in dry season in all types of soil; the diversity and relative abundance of bacteria were highest in NT sampling area and archaea were most diverse and abundant in YN and NT. We detected the sequence information of 64 phyla,164 classes,271 orders,330 families and 484 genera of bacteria, where Proteobacteria, Actinobacteria, Chloroflexi and Acidobacteria were the four most populated phyla; about 40% of the archaeal sequence were unknown sequences and the rest 60% of sequences belong to 3 phyla,5 classes,8 orders,7 families and 7 genera, where Thaumarchaeota (Cenarchaeum) accounted for about 50%; about 60% of fungal sequences have uncertain classification information and the rest belong to 6 phyla,17 classes,37 orders, 53 families and 63 genera, which mainly belong to Ascomycota and the relative dominant species was Gibberella. Further analysis showed that the diversity and composition of bacterial community were more impacted by season changes rather than soil types. In the dry season, nitrogen, total nitrogen and organic matter had greater impact on the overall bacterial community diversity; in the rainy season, zinc, manganese and copper had greater impact on the overall bacterial community diversity; the diversity and conposition of Archaea community were almost resistant to the season changes and soil types. Significant differences were only observed in relatively low-abundance communities in different soil. The diversity and conposition of fungal communities were more affected by soil types than by season changes. In the SD sampling area, the diversity of fungi was almost not influenced by soil physiochemical factors; in the YN sampling area, only the total phosphorus affected the diversity of fungi; in the NT sampling area, iron, copper and phosphorus had a greater impact.The microbial ammonia oxidation is the key step of nitrogen cycle and also a rate-limiting. Therefore, th diversity and spatial distribution of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were analyzed by using ammonia monooxygenase subunitA (amoA) as probe. The results showed that the main species of AOA originated from Thaumarchaeota Groupl.la; and the main species of AOB originated from Nitrosomonas and Nitrosopira. In the YN1 sampling area, the composition and distribution of AOA and AOB were mainly impacted bypH and ammonia nitrogen.(NH4+-N); in NT1 sampling area, the community composition of AOA and AOB were mainly affected by nitrite nitrogen (NO2-N). The ratio of amoA between AOA and AOB showed that the number of AOA was only higher than AOB inNTl sampling area, while in the area affected by human activities AOA is dominant in ammonia oxidizatioa The results implied that the diversity and distribution of AOB was more sensitive to soil physico-chemical factors, and AOA was more sensitive to anthropogenic disturbance.We revealed the evolution and coexistence pattern of microbial community through the analysis of the number, composition and diversity of microbial communities in different seasons and soil types as well as their relationship with soil physico-chemical factors. In the meantime, we also performed preliminary study on ammonia-oxidatizing microorganisms, which played an important role in wetland nitrogen cycling. Combined with metagenomic data in the future, this study provides fundamental knowledge for study of nitrogen cycle mechanism in the regioaIn summary, microbial communities in Napahai plateau wetland soil have unique diversity and composition. Due to the deterioration of the natural environment and intensified human activities, microorganisms adapt to the degrading soil through varying their number, composition and diversity. From the perspective of microbiology, we again emphasized the importance of protection and restoration of Napahai plateau wetland, which also provides theoretical and practical basis for wetlands protection. |
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