Silicon (Si) was a basic element for many aquatic organisms and its biogeochemical cycle played an extremely important role in estuarine coastal ecosystems. Ecotone

as the across area of different typical vegetations

its ecological edge effect was obvious. However

little was known about the role of ecotone in these processes and most focus on typical vegetation

sediment and porewater. The Shanyutan wetland was the largest tidal wetland in the Min River estuary

southeast China. Yet the related researches had been only carried on about porewaters and sediments while little was known about Si distribution in typical vegetation communities and its ecotones. Two transects from land to sea were laid in July 2015 to analyze the spatial distribution of Si in plant-soil systems in typical vegetation communities and ecotones. Results showed that the biogenic silica content in vegetation of ecotones was higher than the vegetation of typical communities while the spatial distribution of different vegetations had significant differences (p>0.05)

and the contents in Phragmites australis

Cyperus malaccensis

Spartina alterniflora and Cyperus compressus were 15.66 mg/g

9.09 mg/g

7.17 mg/g and 7.77 mg/g

respectively. The different vegetation tissues in high tide beach contained more biogenic silica than those in low tide beach. The aboveground parts of vegetation

such as litter

stem and leaf with the contents of 13.40 mg/g

12.49 mg/g

11.72 mg/g and 6.58 mg/g

respectively

had more biogenic silica contents than underground roots. Contrary to typical vegetations community

the allocation proportions of biogenic silica in underground tissues were higher than those in aboveground tissues in ecotones (P.australis and C.malaccensis) of the Min River estuary wetland. Biogenic silica contents in surface soil between two transects showed the same trend in low tide beach and the opposite trend in high tide beach. And the available silicon contents in surface soil between two transects showed a same trend from land to sea. This study found that the differences of ecological characteristics of different vegetations and its growth conditions

and discrepancies of topographic and hydrological conditions caused by tide might affect the accumulation

absorption and spatial distribution of silicon in wetland

this would be of great significance for studying the biogeochemistry of Si in estuarine tidal wetland.