| River wetland has high primary productivity,being an important interface for studying the transport process and circulation process of nutrient elements from land to sea,thus making it be an extremely important area for the study of biogeochemical cycle.Silicon is an rich content element in soil.Studying the distribution characteristics of soil and plant silicon in wetlands along rivers is of great significance to further understand the biogeochemical cycle of silicon in wetland ecosystem.With the research object of the Min River wetland in Fujian province,through the field sampling and indoor experiments.The distribution characteristics of silicon were studied.The distribution characteristics of silicon in the plant-soil system are analyzed.The spatial distribution rules and influencing factors of different wetland types are summarized.The main study results are as follows:（1）The total silicon content of soil along the downstream of Min River fluctuates from land to sea,changing between 28.37～337.41 mg·g-1,with the average content of187.36 mg·g-1.The average total silicon content of freshwater wetland is 185.46 mg·g-1.City river section is 195.75 mg·g-1.Estuary is 179.79 mg·g-1.In the direction of 0～60 cm profile,the trend of soil total silicon content with depth is very different,with the maximum change of E-Spartina alterniflora being between 109.31-273.33 mg·g-1,and A-Pinellia ternata variation being between 209.07～278.12 mg·g-1.（2）The soil available silicon content in the downstream wetland of Min River varies from 7.27～618.58μg·g-1except for S23 point(1662.22μg·g-1).Average content is248.85μg·g-1.The soil available silicon average content is 155.84μg·g-1in freshwater river section,249.66μg·g-1in city river section（except S23）,and 287.49μg·g-1in estuary.In the section direction of 0～60 cm,the available silicon content shows an obvious gradual decrease trend from surface to deep layer.Except for C-Cyperus malaccensis,the available silicon content of all other points changes little vertically.（3）Different types of wetlands in the downstream of Min River,except for sand beach,the variation of total silicon content of other wetlands is large and showing no obvious upward trend from land to sea.Among them,the average total silicon content of flood plain wetland is 212.83 mg·g-1.While the content of total silicon is 161.53 mg·g-1in herbal swamp wetland,183.97 mg·g-1in intertidal salt water marsh wetland,266.75mg·g-1in sand beach wetland,142.05 mg·g-1in aquafarm wetland,251.96 mg·g-1in shrub marsh wetland,and 184.11 mg·g-1in silty beach wetland.（4）The variation of available silicon content of different wetland types in the downstream of Min River is large.And the available silicon content of various types of wetland is generally increased from land to sea.Among them,the average available silicon content is 223.76μg·g-1in flood plain wetland,206.61μg·g-1in herbal swamp wetland,327.81μg·g-1in intertidal salt water marsh wetland,89.62μg·g-1in sand beach wetland,273.97μg·g-1in aquafarm wetland,287.96μg·g-1in shrub marsh wetland,and478.97μg·g-1in silty beach wetland.（5）The BSi content of different species of plants in the downstream wetland of Min River varies greatly,between 4.42～38.98 mg·g-1.The BSi content of underground roots is relatively lower than other tissues.While the BSi reserves are mainly concentrated in the aboveground tissues,basically in line with the trend of“terminal concentration”.From the perspective of each organ,the BSi enrichment coefficient of drybody,leaf and stalk is higher.And the root is the lowest.In terms of the transfer coefficient,the ratio of most above-ground tissues to underground root BSi is higher than1.This shows that the roots of various plants in the downstream of Min River are relatively weak to enrich soil silicon.And the ability of other aboveground tissues is relatively strong.（6）The plant BSi content is negative correlation with population density,and positive correlation with plant height.The negative correlation between root BSi content and soil salinity、root biomass indicates that the root BSi content in offshore areas is lower than that in far sea areas maybe because of the limitation of salinity stress.（7）Through correlation analysis,stepwise linear regression analysis and principal component analysis,it is found that the key factors affecting the distribution of silicon content in different wetlands in the downstream of Min River include particle size,water content,EC,p H and nutrient salt.For different river sections and different types of wetland soil,the influencing factors are also different. |
