| As one of the three important ecosystems,wetland has up to 40%of the terrestrial carbon storage in 6%of the global land area,which is the main terrestrial carbon sink and plays an important role in the global carbon cycle.In order to better protect and develop the wetland ecosystem in Naolihe Reserve,this study selected Naolihe Reserve marsh wetland as the research object,and conducted field survey and retrieved the distribution area and carbon storage of forest marsh(FS),shrub marsh(SS),marshy meadow(SM)and herbaceous marsh(HM)in Naolihe Reserve in combination with Landsat-8 remote sensing image.To study the changes in soil organic carbon content and storage,as well as the stability of soil organic carbon pool under different vegetation types in the Naolihe Reserve swamp wetland,and to reveal the response of soil organic carbon to soil physicochemical factors.The contents of soil organic carbon and density components in different vegetation types under different restoration years were analyzed by selecting Scirpus triqueter(ST),Deyeuxia angustifolia(DA),Phragmites australis(PO),and Salix rosmarinifolia(SR)with different restoration years as the objects,and taking adjacent farmland as the control,to provide a scientific basis for evaluating the carbon fixation effect of different vegetation restoration types in Naolihe Wetland.The main conclusions are as follows:(1)The soil organic carbon(SOC)of wetland soil in the study area decreased significantly with the increase of soil depth in the vertical direction.There was no significant difference in the content of soil organic carbon among different wetland vegetation types(P>0.05),and the size relationship was SM>HM>SS>FS.In the protected area,there was a significant positive correlation between the content of SOC in 0-30 cm soil and soil physical and chemical factors(P<0.05),and soil TN was the most important factor affecting the distribution of SOC.(2)The distribution of light component and recombined organic carbon(LFOC,HFOC)in wetland soil in the study area was similar to the results of SOC.Soil depth had a significant impact on LFOC and HFOC(P<0.05),both of which decreased with the increase of soil depth;Vegetation types had no significant impact on the content of light component and recombinant organic carbon in soil(P>0.05).The LFOC/SOC values of soil decrease with the increase of soil depth,and the stability of soil organic carbon pool increases with the increase of soil depth.The stability degree of soil organic carbon pool in the range of 0-30 cm is as follows:SS>SM>HM>FS.(3)The physical and chemical properties of wetland soil in the study area change with the increase of the number of years of returning farmland,with soil SOC,MC,EC,and TDS all showing a trend of first increasing and then decreasing with the increase of the number of years of returning farmland,while p H remains weakly acidic.The SOC content of ST,DA,and PO soils reached the maximum at 6 years,and was significantly affected by the number of years of returning farmland.The vegetation restoration type had a significant impact on soil SOC content changes after 6 years of returning farmland,and this impact weakened after 9 years.(4)The number of years of land conversion had a significant impact on soil LFOC(P<0.05),similar to the trend of SOC change.The LFOC of ST,DA,and PO soils showed a trend of first increasing and then decreasing with the increase of land conversion years,while the LFOC of SR soils increased with the increase of land conversion years.The LFOC/SOC values of the four types of vegetation restoration after land conversion were significantly higher than those of farmland when the land conversion period was 6 years,and the soil carbon pool was extremely active at this time;After 9 years,soil LFOC/SOC decreased and soil organic carbon pool returned to stability.(5)Soil organic carbon storage(SOCS)of four types of wetland vegetation is shown as follows:SM(49.48×10~6 t)>HM(13.98×10~6 t)>FS(7.18×10~6 t)>SS(3.16×10~6 t),the total organic carbon storage of wetland soil in Naolihe Reserve is 73.81×10~6 t.The type of vegetation restoration also affects the soil carbon sequestration effect,with ST,DA,and PO showing certain soil carbon sequestration effects at 6 and 12 years of returning farmland,while the soil carbon sequestration effect is not significant at 9 years;SR showed a certain effect of soil carbon fixation when returning farmland for 9 years.From the average carbon sequestration rate of the soil,the DA,PO,and SR communities in the restoration of returning farmland as a whole exhibit carbon sink effect,while the ST community exhibits carbon source effect. |
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