Effects Of Spartina Alterniflora Invasion In A Seaward Direction On Sulfur Storage And Its Migration And Transformation Processes In Marsh Soils Of The Min River Estuary

Spartina alterniflora is one of the most important biological invasive species in coastal areas of my country.It originally grew on the Atlantic coast.It was introduced in 1979 for the purpose of promoting siltation and preventing coastal erosion.Since the invasion of Spartina alterniflora can have a profound impact on the stability and health of the estuary wetland system,the research on its impact on the ecological process of the estuary wetland,especially the key process of biogenic element cycle,has attracted more and more attention.Since 2002,Spartina alterniflora has invaded the Shanyutan wetland in the Minjiang River estuary,and has invaded both landward and seaward along the main tidal creek from northwest to southeast,respectively as a whole.After that,the invasion area of Spartina alterniflora increased year by year,with an average annual increase rate of 9.8%.At present,the related studies on the invasion of Spartina alterniflora in the Minjiang River estuary mainly focuses on the impact of its land invasion on the spatial and temporal distribution of marsh soil carbon,nitrogen,phosphorus,sulfur,and silicon,and there are more studies on carbon and nitrogen.However,there are few reports on the sulfur storage of marsh soil and its migration and transformation process,under the influence of Spartina alterniflora seaward invasion.In this paper,the bare flat(BF,before invasion),S.alterniflora marsh after seaward invasion for one year(SA?)and S.alterniflora marsh after seaward invasion for three years(SA)in Shanyutan of the Minjiang River estuary were studied.Based on the method of space-fortime substitution,by collecting soil samples of different invasion stages,combining in situ sampling,indoor simulation experiments and open system cultivation experiments,the effect of Spartina alterniflora seaward invasion on the occurrence of inorganic sulfur in marsh soils were discussed.Meanwhile,the influence of Spartina alterniflora seaward invasion on the process of soil sulfur mineralization and the vertical movement of SO₄^2-in marsh soils were clarified.On this basis,the impact of Spartina alterniflora seaward invasion on the occurrence and migration and transformation of sulfur in marsh soil was evaluated.Results were as follows:i)The seaward invasion of Spartina alterniflora altered the contents of inorganic sulfur forms and its content and storage of TIS in marsh soils.The overall performance of inorganic sulfur in different forms of marsh soils in winter and spring was H₂O-S>HCl-Soluble-S>Adsorbed-S>HCl-Volatile-S.Compared with BF,the TIS reserves in SA and SA?soils increased by 0.24%and 7.85%in spring,while in winter,the TIS reserves in SA and SA?soils increased by 7.22%and 23.48%,respectively,indicating that the Spartina alterniflora seaward invasion increased the marsh soil inorganic sulfur storage and increased the supply level of plant sulfur nutrients.On the whole,the increased in the stocks of TIS in SA and SA?soils mainly depend on the contribution of the increase in the stocks of H₂O-S and Adsorbed-S,which improves the supply capacity of available sulfur in marsh soils to a certain extent,thereby helping to accelerate its seaward invasion.ii)The sulfur mineralization characteristics of different marsh soils under the influence of Spartina alterniflora seaward invasion are quite different.The mineralization potential of BF soil is lower than that of SA and SA?,indicating that the seaward invasion of Spartina alterniflora has changed the physical and chemical properties of marsh soil(especially grain size)to a certain extent to promote the mineralization of sulfur in marsh soils and increased its potential sulfur supply capacity.In spring,the sulfur mineralization potential of SA,SA?and BF soils under two water conditions in different marshes is higher than that in winter,indicating that the Spartina alterniflora seaward invasion has increased the sulfur mineralization potential of marsh soil in winter as a whole,and it may provide sufficient sulfur nutrients for its buds to germinate in the following spring.iii)The seaward invasion of Spartina alterniflora changed the vertical migration characteristics of inorganic sulfur in marsh soil to varying degrees.Compared with BF,the vertical migration capacity of SO₄^2-in SA and SA?soils is weakened to a certain extent,indicating that with the seaward invasion of Spartina alterniflora,its strong silt-promoting effect weakens the vertical migration capacity of SO₄^2-,which in turn is beneficial to the maintenance of available sulfur nutrients in the soil to a certain extent.This paper found that,under the influence of Spartina alterniflora seaward invasion,soil inorganic sulfur reserves,organic sulfur mineralization potential and vertical migration characteristics of inorganic sulfur in different marshes have changed to varying degrees.The seaward invasion of Spartina alterniflora is very likely to increase the supply and maintenance of available sulfur nutrients in the soil by increasing the storage of soil inorganic sulfur,increasing the potential of soil sulfur mineralization,and reducing the migration capacity of soil inorganic sulfur nutrients,and then it may be helpful to accelerate its seaward invasion.