Distribution Characteristics And Influencing Factors Of Soil Inorganic Carbon Reserves In Typical Estuary Wetlands Of Jiaozhou Bay

Soil inorganic carbon?SIC?is a significant component of soil carbon,which is crucial for assessing regional soil carbon storage,exploring terrestrial carbon circulation,and alleviating global greenhouse effect.In this paper,the Dagu River and the Yanghe River estuary wetland of Jiaozhou Bay were selected as the study area s.Soil samples were collected by stratified sampling in the mudflat paralleled to the coastal zone and the river flat perpendicular to the coastal zone.We examined the SIC content,soil bulk density,ion content,and soil physical and chemical properties.Duncan method was used for data saliency analysis and Pearson method was used for data group correlation analysis.According to analyzing results,we explored the spatial distribution characteristics of SIC reserves,the disturbance of external factors such as land use/vegetation cover and the effects of soil physical and chemical properties on SIC reserves.The purpose of this study is to provide a reference for further improving soil carbon cycle and to improve the quantitative level and accuracy of carbon flux estimation in coastal estuary wetlands.The main findings were provided as follows:?1?The distribution of soil inorganic carbon?SIC?reserves in four types of wetlands was as follows:aquaculture ponds>mudflat>river flat>Spartina alterniflora marsh.On the vertical section,the SIC reservesin 0–20 cm and 40–60 cm soil depth was obviously higher.These phenomena were not only related to the physical and chemical properties of the sample soil itself,but also to its geographical location,seawater tide,vegetation cover and anthropogenic activities.?2?In the horizontal direction,the SIC reserves of the mudflat reached the lowest value at the estuary of the river,showing a trend that the farther away from the estuary of the river,the higher the SIC reserves were.The influence of the ocean tides scouring on SIC reserves at the estuaries of rivers was the main factor leading to this phenomenon.However,the SIC reserves of river flat decreased first and then increased with the rising distance from the sea.Due to the different distance from the sea,the SIC reserves were affected by oceanic factors and anthropogenic activities in varying degrees.The SIC reserves of near-shore Spartina alterniflora march were lower than that of far-shore Spartina alterniflora march,and the growth status of plants themselves was the dominant factor.The SIC reserves of different sample sites in aquaculture ponds were not significantly different.In the vertical section,the SIC reserves of 40–60 cm deep soil layer in the mudflat were the highest.This was due to the dilution of inorganic carbon in surface soil by ocean tides,and the addition of inorganic carbon to deep soil by leaching.The SIC reserves in the 0–20 cm topsoil of the river flat were relatively high,which reflected the results of SIC migration synthetically affected by climate,topography and anthropogenic factors.The SIC reserves of 40–60 cm deep soil in Spartina alterniflora march were higher,and the main influencing factors were the distribution of roots and the leaching of seawater tides.The SIC reserves of 0–20 cm topsoil and 40–60 cm deep soil in aquaculture ponds were higher,The ion concentration caused by water evaporation,microbial decomposition and seawater leaching comprehensively affected the vertical profile distribution of SIC reserves.?3?Invasion of Spartina alterniflora reduced SIC reserves,which was closely related to plant photosynthesis and leaf coverage;while aquaculture activities increased SIC reserves,aquaculture disturbance and biological activities of algae were the main factors.SIC reserves were positively correlated with SIC content,soil bulk density,soil salinity and soil pH.The correlation analysis showed that SIC reserves were positively correlated with K⁺?Na⁺?Mg²⁺?Ca²⁺?Cl^-?HCO₃^-?SO₄^2-and SIC?CaCO₃?content.Among them,there was a significant positive correlation with K⁺?Cl^-,and was extremely positively correlated with the contents of Na⁺?Mg²⁺?Ca²⁺?HCO₃^-?SO₄^2-and SIC?CaCO₃?content.