Distribution Characteristics Of Soil Organic Carbon In Mountain Marsh Of The Southern Zhejiang Province

Soil carbon pool is the largest carbon pool in terrestrial ecosystem and plays an important role in global climate change.Soil active organic carbon can reflect the change of soil carbon pool sensitively and has important significance for carbon balance.Mountain marsh plays a key role in protecting regional biodiversity and maintaining the "water tower"function of river headwaters.The difference of regional climate and vegetation type may lead to the unique organic carbon content and distribution characteristics of mountain swamp which are different from other swamp wetlands.Therefore,the study on the distribution characteristics of soil organic carbon in mountainous swamps can provide basic data for the in-depth understanding of soil carbon sink function and carbon cycle process of different types of wetlands.This study relies on Wangdongyang and Dayang lake wetland reserve located in the south of Zhejiang province,taking the typical mountain swamp(herbaceous swamp and forest swamp),mixed coniferous and broadleaved forest in the reserves as research objects,collecting soil samples at different depths(0-10cm、1 0-30cm、30-60cm、60-100cm)under different vegetation types,analyzing and comparing the content and distribution of SOC,DOC,MBC,ROC,POC,LFOC in soli,the herbaceous marsh of Dayanghu was taken as reference wetland,evaluating of the quality of organic carbon restoration of the herbaceous wetland in Wangdongyang reserve;using vegetation type method to estimate the organic carbon density and forest swamp,herbaceous swamp,mixed coniferous and broadleaved forest of Wangdongyang reserve and Dayanghu herbaceous swamp soil through the longitudinal fitting function of organic carbon.Finally,using 210Pb dating method to explore the carbon fixation rate of Wangdongyang wetland soil and Dayanghu wetland soil within 1m depth.The research results show that:(1)The soil organic carbon content of different vegetation types decreases with the decrease of soil depth.The average organic carbon content of herbage swamp,forest swamp and mixed coniferous and broadleaved forest were 79.378g/kg,34.158g/kg and 43.679g/kg,respectively.The soil organic carbon content in the herbaceous marsh type was significantly higher than that in the other two vegetation types.The higher vegetation litter returns in herbaceous marshes provide sufficient carbon sources.(2)The DOC of forest swamp,herbaceous swamp and mixed coniferous and broad-leaved forest in Wangdongyang keeps stable in each soil layer,while LFOC and POC significantly decreases from 0-10cm to 10-30cm in the surface layer.In soil layers of 0-10cm,10-30cm,and 30-60cm,there was no significant difference between the proportion of DOC in soil organic carbon in forest swamp and coniferous and mixed broad-leaved mixed forests,but both of them were significantly higher than that in herbage swamps,and the proportion of granular organic carbon in soil organic carbon in herbage swamps was significantly higher than that in forest swamp and coniferous and mixed coniferous and broadleaved forest.Under the influence of soil organic carbon and many environmental factors,the content of active components of organic carbon varies with different vegetation types,but the components are closely related.(3)The soil organic carbon content of herbaceous swamp wetland at 0-10cm,10-30cm,30-60cm in Wangdongyang is lower than that of Dayanghu herbaceous swamp natural wetland.As for the active organic carbon component,the DOC content of Wangdongyang herbaceous wetland has a small difference with that of Dayanghu herbaceous wetland,and the MBC and ROC content of Wangdongyang herbaceous wetland is higher than that of Dayanghu herbaceous wetland.Its overall expression is that the organic carbon and active organic carbon components of grass swamp have not yet recovered to the pre-cultivation level.(4)Wangdongyang forest swamp has a soil organic carbon density of 2.07 kg/m~2,mixed coniferous and broad-leaved forest has a soil organic carbon density of 2.61 kg/m~2,herbaceous swamp has a soil organic carbon density of 14.17 kg/m~2,and herbaceous swamp has a soil organic carbon density of 18.99 kg/m~2.The results showed that the herbaceous marshes had strong carbon sequestration ability,but human activities had serious influence on the carbon sequestration ability of herbaceous marshes.(5)Wangdongyang has a soil deposition rate of 0.111～0.301cm/a,a carbon sequestration rate of 0.013～0.056 g/(cm~2·a).Dayanghu has a soil deposition rate of 0.155～0.684cm/a,and a carbon sequestration rate of 26.203～120.786 g/(cm~2·a).The rate of carbon sequestration in herbaceous marshes is much higher than that in forest marshes.According to the research results,Wangdongyang herbaceous marshes have stronger carbon fixation and assimilation capacity than forest marshes and coniferous mixed forests.After 20 years of return to wet recovery,the loss of wetland soil organic carbon caused by reclamation failed to return to the previous level.The impacts of reclamation on the active components of soil organic carbon are different.On the one hand,the content of particulate organic carbon and light organic carbon is lower than that of natural wetlands;on the other hand,it promotes the formation of microbial carbon.Soil organic carbon density is different with different vegetation types.In wangdongyang wetland area,the organic carbon density of herbage marshes is higher than that of forest marshes and coniferous mixed forests.For herbaceous marshes,organic carbon density of herbaceous marshes in dayanghu is higher than that in wangdongyang restoration wetland herbaceous marshes.The deposit age of soil at the depth of 1m of wangdongyang and dayanghu was about 1350s,and the soil deposition rate and carbon fixation rate of dayanghu were much higher than that of wangdongyang.Compared with other swampy wetlands,it indicates that the deposition rate of southern Zhejiang province swampy wetland is fast in the shallow soil layer,and the deposition rate is slow in the whole soil layer development process.The results indicate that the carbon sink function of marshes is the result of long-term slow accumulation.