崇明东滩湿地不同潮汐带入侵植物互花米草根际细菌的多样性

The diversity of invasive plant Spartina Alterniflora rhizosphere bacteria in a tidal salt marshes at Chongming Dongtan in the Yangtze River estuary

为了调查崇明东滩湿地入侵植物互花米草(Spartina Alterniflora)在不同潮汐带和季节根际细菌的多样性与丰富度,以本地植物芦苇、海三棱藨草(P.australis和S.mariqueter)和光滩为对照实验研究,在崇明东滩湿地10样点采集根际土壤和光滩土壤,通过PCR-DGGE分子生物学等技术并结合传统培养方法对土壤细菌进行分析研究。研究表明:东滩湿地不同潮汐带的植物根际细菌群落丰富度和多样性不同,在夏季中潮带的根际细菌丰富度(P=0.021<0.05)较高,各个潮带的植物根际细菌在夏秋季有高多样性,其中中潮带的植物根际细菌平均多样性指数最高(H=4.20)。在中潮带入侵物种互花米草根际细菌的丰富度和多样性要显著高于本地植物芦苇和海三棱藨草,其中海三棱藨草的根际细菌在夏季略高。崇明东滩湿地入侵植物互花米草根际细菌与本地植物相比较具有较高的多样性,而且外来种互花米草对湿地土壤微生物群落结构有着较强影响;入侵种互花米草根际细菌的高丰富度和多样性可能是其成功入侵东滩湿地的一个重要因素。

The invasive species of Spartina alterniflora, as an ＇ ecosystem engineer＇ was introduced into many places in China, now, had rapidly and widely invaded into the Chongming Dongtan wetland since 1990s. Microorganisms are important components of wetland ecosystems, performing a range of vital ecosystem functions. But, we have not known how microorganisms have an influence on the invasion of Spartina alterniflora in Chongming Dongtan. In order to study the bacterial diversity and abundance in rhizosphere of invasive plants Spartina Alterniflora growing in different tidelands of Chongming Dongtan Wetlands for different seasons, we selected 10 samples collection points, which distributed on the tidal zones with plant and the blare flat zone without plant in Chongming Dongtan wetlands. The tidal zones contain low-tide zone, mid-tide zone and high-tide zone. Total DNA was extracted from soil samples, and 16S rRNA gene-based PCR was performed. A comparative study of diversity of microorganisms in rhizosphere soils of invasive exotic species （ Spartina alterniflora ） and two native species （ Phragmites australis and Scirpus mariqueter ） was conducted by denaturing gradient gel electrophoresis （DGGE） of these PCR products, representing microorganisms in rhizosphere soils.. Results showed that diversity and abundance of bacterial community were different in the rhizosphere of Spartina alterniflora, Phragmites australis and Scirpus mariqueter in the low-tide zone, mid-tide zone and high-tide zone in Chongming Dongtan wetlands..We found that, in summer, rhizosphere bacterial communities in mid-tide zone had higher abundance than those in low-tide zone and high-tide zone （P = 0. 021 〈 0. 05）. A higher diversity of bacteria in the rhizosphere soils of these plants was observed in summer than in other seasons. The average diversity index of bacterial community was calculated and was found to be the highest in mid-tide zone （H = 4.20）. The abundance and diversity of bacterial community in invasive species Spartina alterniflora rhizosphere were significantly higher than in the local plants P. australis and S. mariqueter in mid-tide zone, and the abundance and diversity of S. mariqueter rhizosphere bacteria in summer slightly higher than in other seasons. Also the abundance and diversity of S. alterniflora rhizosphere bacteria were significantly higher in tidal soils than those in the mudflat soils. Overall, these results indicated the tides had a strong influence on the abundance and diversity of the plants rhizosphere bacteria. And the exotic species Spartina alterniflora had a favorable influence on soil microbial community in wetland. We reasoned that high diversity and abundance bacteria in rhizosphere maybe were an important for the invasion of Spartina alterniflora. A higher diversity of bacteria in the rhizosphere soils of these plants observed in summer revealed that the summer is more beneficial for bacteria living in vicinity of plant roots. The fact that the flourishing Spartina rhizosphere was associated with large bacteria assemblage suggested that the high diversity and abundance of microorganisms might be identified as one of the important factors of Spartina invasion mechanisms.