Restoration-driven Distribution Of Wetland Soil Carbon And Environmental Implications At Jingjiang Estuary,Fujian,China

Estuary wetland is an important wetland ecosystems that exists between terrestrial and marine ecosystems.The study was aimed to find out the dynamics of soil C,especially black carbon(BC)and total nitrogen(TN)in southeast China to 1 m depth following the restoration with mangrove(Kandelia obovata,Aegiceras corniculatum,Avicennia marina,Acanthus ilicifolius,Bruguiera gymnorhiza,Rhizophora stylosa)under different plants and different planting density before the restoration and during the two years' restoration at Jinjiang estuary wetland to provide support for short/long term restoration and management strategies of that may offset negative aspects of climate change in estuarine wetland.The main results are concluded below.(1)Before the restoration,TOC(total organic carbon)content at the average of 13.44g/kg,the contents go to 13.22 g/kg and11.73g/kg after one year and two years' restoration.The TOC content had a difference with the density and the plantation.The maximum appeared in the upper between 10cm-40 cm,a few appeared at the depth of 60 cm and the minimum can be different.It may due to the fact that high decay rates likely offset increases in litter inputs to soil and there was an interannual variability for the artificial mangrove wetland.(2)The BC content was 2.02g/kg before the plantation,the contents go to1.94 g/kg and1.90g/kg after one year and two years' restoration.The average of the BC content slightly decreased and the BC content after the afforestation and the BC content had a significant difference with the density of the restoration.The slight decrease of BC content can be seen from this study.It might be caused by changes in water management and evaporation rates during the afforestation.Longer durationof sunshine also the reason of the loss of BC.(3)According to the detection we can find that soil texture are all loam.The content of silt,clay and sand were 16.69-22.23%,68.79-74.75%,6.04-10.5%,respectively.Sediments were mainly silt-sized cause clay and silt size fraction are the influencing factors in forming and stabilizing soilaggregates.(4)TN content had a difference(p<0.05)with the density of the plot.On the plot with Kandelia obovata +Avicennia marina+Sesuvium portulacastrum the difference is significant(p<0.01)and sediment can produce the most TN(2.37g/kg)with mangroveplanted under the density of 0.5×0.5 m.Because of the tital variation,the content of N decreased after the restoration.And on the other hand,the fact that high decay rates likely offset increases in litter inputs to soil also cause the decreasement of N.(5)The C/N of the studied area varies from 4.74-11.78 with an average of 6.89.Verticaly,ratio at 20-60 cm was higher than the other layers'.It may have some relations with the root system distribution.The organic carbon sources of the wetlands were the interaction source of terrestrial and marine.There's a positive relationship between TOC and TN,TOC and C/N.C/N depends on the input and decomposition of C/N.The evidence that C/N had a difference with TOC content shows us the fact that mangrove had a certain functions on the TOC content.(6)Before the recovery project,the average soil organic carbon density in the sediment of each layer was 2.772kg/m2.There's a slightly decrease of SOCD,the content went to 2.717 kg/m2 and 2.342kg/m2 after one year's and two years' restoration.