Distribution Characteristics Of SiO₂ And The Potential Of Phytolith Sequestration Carbon In Typical Plant Communities And Ecotones In The Min River Estuary

Estuary wetland is one of the most sensitive ecosystems responding to global change and human activities.It is also an important interface for the study of silicon cycle.Silicon is helpful to mitigate global warming.Studying the distribution characteristics of silicon in wetland soil-plant system is of great significance for further understanding the biogeochemical cycling process of silicon and carbon in estuarine wetland ecosystem.In view of this,this study takes the Shanyutan wetland of Min River Estuary in southeastern coastal areas of China as the research object.Through field in situ sampling and laboratory experimental analysis,the change characteristics of soil SiO₂ and its main influencing factors,the accumulation and distribution characteristics of different plants SiO₂ in estuary wetland and their competitive mechanism are analyzed,and the carbon sequestration potential of Phytolith in Min estuary wetland is discussed.This paper summarizes the characteristics of silicon in soil and plant and the biocycle of silicon-carbon coupling in plant in Min River Estuary.The main conclusions are as follows:?1?In Min River Estuary,the highest SiO₂ content appeared in winter and the lowest in summer in the Cyperus malaccensis wetland,Spartina alterniflora wetland and their ecotone wetland.The average content was as follows:Cyperus malaccensis wetland?197.67 mg/g?<ecotone wetland?201.21 mg/g?<Spartina alterniflora wetland?210.33mg/g?.There were significant differences among the three wetlands?P<0.05?;?2?The content of SiO₂ in 0-60 cm soil layers of different vegetation wetlands in Min River Estuary had significant difference in different months?P<0.05?.The content and reserves of SiO₂ in different soil layers were higher in the upper layer?0-30 cm?than in the lower layer?30-60 cm?;?3?Compared with domestic and foreign studies,the content of SiO₂ in the wetland soil of Min River Estuary is relatively low,and the distribution characteristics of SiO₂ in different plant wetlands are affected by multiple environmental factors.The proportion of sand content plays a decisive role in affecting SiO₂ content in soil of different plant wetlands.In addition,pH and soil temperature all affect Spartina alterniflora wetland,ecotone wetland and Spartina alterniflora wetland;?4?The average SiO₂ content of Cyperus malaccensis and Spartina alterniflora in the wetland of Min River Estuary showed that the pure community was higher than that in the ecotone,and the order was as follows:pure community of Cyperus malaccensis?27.30 mg/g?>pure community of Spartina alterniflora?22.70 mg/g?>Spartina alterniflora in the ecotone?22.10 mg/g?>Cyperus malaccensis in the ecotone?21.54mg/g?.In the process of spatial expansion of Cyperus malaccensis and Spartina alterniflora,Spartina alterniflora distributes more silicon nutrients to roots to improve root competitiveness.But the Cyperus malaccensis distributes more silicon nutrients to the aboveground parts of plants to improve its competitiveness.Spartina alterniflora invasion significantly affects the ability of silicon absorption and accumulation of Cyperus malaccensis;?5?The ecological characteristics of wetland vegetation in Min River Estuary significantly affected the distribution characteristics of SiO₂ in different plants.There was a significant negative correlation between SiO₂ content in stems and plant density in Cyperus malaccensis and Spartina alterniflora.In Spartina alterniflora,there was a significant negative correlation between SiO₂ content and plant height in different organs except litter and leaves,and there was a significant positive correlation between SiO₂content in leaves and biomass,plant height;?6?PhytOC content of wetland plants in Min River is higher in Nearshore Area than in Offshore area,and PhytOC reserves are higher in pure community than in ecotone.The content of PhytOC was in turn as follows:Phragmites australis pure community?4.14mg/g?>Phragmites australis in the ecotone?3.67 mg/g?>Phragmites australis and Cyperus malaccensis in the ecotone?3.08 mg/g?>Spartina alterniflora pure community?2.70 mg/g?>Spartina alterniflora and Cyperus malaccensis in the ecotone?1.96mg/g?>Spartina alterniflora in the ecotone?1.86 mg/g?>Cyperus malaccensis pure community?1.75 mg/g?;?7?It is estimated that the carbon storage of Phragmites australis,Cyperus malaccensisa and Spartina alterniflora in Shanyutan wetland of Min River estuary by phytosilicon accounts for 0.27%,0.15%and 0.07%of the plant carbon storage,respectively,and the carbon sequestration by phytosilicon is 1.09 t,0.4 t and 2.65 t annually,respectively.The carbon sequestered by Spartina alterniflora in China is291.89t per year through phytosilicon,which can be stored for a long time.