The Changes Of Soil Factors During The Ecological Invasion Of Spartina Alterniflora

The special location of coastal wetland creates unique conditions for the soil formation and development.Plants and soil are important factors of vegetation succession.Spartina alterniflora is the most threatening invasive species in Yancheng Coastal Wetland.The invasion of S.alterniflora into the native Suaeda salsa marsh reduces the ecosystem function of Yancheng Coastal Wetland.In order to study the effects of S.alterniflora invasion on the dynamic changes of soil factors and how soil factors alter the invasion process of S.alterniflora,we took soil samples from the S.alterniflora single dominant community,the S.salsa single dominant community and the six gradient zones in the ecotone of S.alterniflora and S.salsa communities at depths of 0-10,10-30 and 30-60 cm,in Yancheng Coastal Wetland.We investigated the plant traits and analysed the main soil factors.The results showed that:(1)The research on the single dominant communities in two study area found that the soil bulk density(BD)and average grain size(MZ)of the three layers in S.alterniflora community were lower than that in S.salsa community,while the water content(SWC),total organic carbon(TOC),total nitrogen(TN),total phosphorus(TP)were higher.There were no significant differences in SWC,BD,TOC,TN and TP between the soil layers in the plant communities.However,p H,Mz and DS showed vertical differences.SWC,TOC and TN were significantly positively correlated in the three layers,while DS was highly correlated with other factors in the surface layer.(2)In the ecotone of S.alterniflora and S.salsa communities,the soil characteristics had regional differences.SWC,TOC,TN,TP,available phosphorus(AP)and labile organic carbon(LOC)in the three layers across the habitat gradients in Yancheng Nature Reserve were higher than those in Dafeng Nature Reserve,while BD,p H and MZ were lower.(3)Soil factors except Mz and TP at 0-10 cm were significantly different from those at the other depths.In the ecotone,compared with S.salsa,the surface layer of S.alterniflora had higher SWC,TOC,TN,and lower BD,DS and p H.With the transition from the interior to the edge zone of S.alterniflora community,the plant biomass,height and coverage decreased.SWC,TOC and TN of surface soil generally decreased,while BD and p H increased.But DS,MZ and TP showed no significant difference between different zones.The correlation between soil factors in the surface layer was higher than that in the other two layers.In the surface and middle layers,there were significant positive correlation between TOC,TN and AP,while p H was negatively correlated with TOC and TN.But SWC and BD in the three soil layers were negatively correlated.(4)In the ecotone,redundance analysis(RDA)showed that the surface soil factors and community characteristics presented the gradient distribution pattern.SWC,BD,DS,p H,TOC,TN at 0-10 cm were important factors that affect community characteristics in different gradient zones.(5)The surface soil factors had the greatest influence on the growth of S.alterniflora.SWC,TOC,TN were positively correlated with the growth of S.alterniflora,while BD,p H,MZ were negatively correlated with the growth of S.alterniflora.In the research,the soil factors of Yancheng Coastal Wetland have differences between different plant communities and soil layers.The short-term invasion of S.alterniflora alters soil factors mainly in the surface layer,which is shown as increasing SWC,TOC,TN and reducing p H,DS,BD.With the increase of invasion age,TOC and TN show cumulative effect.The stable S.alterniflora community living for a long time can also significantly increase TP and reduce Mz.The increase of SWC,TOC,TN may promote the comparative competitive advantage of S.alterniflora.