Carbon,Nitrogen And Phosphorus Stoichiometries Of Soil,Microbial Biomass,and Extracellular Enzyme Activities Across A Transect In The Tidal Wetland Of The Jiulong River Estuary,China

To explore the impact of sea-level rise on soil carbon（C）,nitrogen（N）and phosphorus（P）cycling in the tidal wetlands,we investigated contents and stoichiometries of C,N and P in a cross transect（span=1.7 km;depth=～2.8 m）in a coastal saltmarsh of the Jiulong River Estuary in the East China Sea,with vegetation varying from Kandelia obovate,ecotone I（dominated by Kandelia obovate）,ecotone II（dominated by Spartina alterniflora）,Spartina alterniflora and tidal flat.（i）From landward to seaward,the concentrations of SOC,TN,TP,DOC,DON,DOP,NH₄⁺and PO₄^3–all decreased.The values ofδ¹³C ranged from-27.77‰to-20.52‰,while the values ofδ¹⁵N ranged from 6.70‰to 5.92‰,suggesting that the soil organic matter mainly deriving from plants.（ii）From landward to seaward,the concentrations of MBC,MBN,MBP,the biomass of G+,G-,arbuscular mycorrhiza fungi,actinomycetes and the activity of NAG all decreased.The activity of BG and CBH increased first then decrease,and the maximum at ecotone II（dominated by Spartina alterniflora）.The activity of AP increased first then decrease,and the maximum at Spartina alterniflora.（iii）From landward to seaward,the value of soil C:N,soil C:P,soil N:P,MBC:MBN,the extracellular enzyme activities（EEAs）N:P all decreased.The value of MBC:MBP,EEAs C:N,EEAs C:P increased first then decrease,and the maximum at ecotone II（dominated by Spartina alterniflora）.The value of MBN:MBP increased first then decrease,and the maximum at Spartina alterniflora.CUE decreased first then increase,and the minimum at ecotone II（dominated by Spartina alterniflora）.NUE and PUE increased first then decrease,and the maximum at ecotone I（dominated by Kandelia obovate）and Spartina alterniflora,respectively.Microbial C limitation increased first then decrease,and the maximum at ecotone II（dominated by Spartina alterniflora）.Microbial P limitation decreased first then increase,and the minimum at Spartina alterniflora.Soil organic matter,microbial element using efficiency,microbial C limitation and microbial P limitation have difference in vegetation,but soil depth is not effect on them.From landward to seaward,the vegetation shifting with the inundation frequency increase,the connection of soil organic matter and the biomass of microbial decrease.CUE decreased first then increase,but NUE and PUE increased first then decrease.