Characteristics And Driving Mechanism Of Soil Organic Carbon Stability In Typical Land Use Types In The Lower Yellow River Alluvial/Sedimentary Areas

Soil organic carbon is the bulk of the terrestrial carbon pool and plays an important role in the global ecosystem carbon cycle,and any small change in it can have an important impact on the stability and functioning of the global ecosystem.Exploring the stability characteristics and driving mechanisms of soil organic carbon is of great significance for a deeper understanding of the global ecosystem carbon cycle.The sediment affected area of the Yellow River is an important grain production area in China,and its material source is mainly sediment from the Yellow River,and the soil fertility is low.The contradiction between high-intensity agricultural farming and soil quality improvement in the region is prominent,and the search for sustainable agricultural development and soil quality improvement are the problems faced by the region.Based on this,taking the typical land use type soil in the sediment affected area of the Yellow River(Kaifeng)as the research object,the content characteristics of soil organic carbon,granular organic carbon(POC)and mineral-bound organic carbon(MAOC)under different land use types and agricultural planting modes were explored through field investigation,soil sample collection,indoor experiment and model analysis,and the stability degree of soil organic carbon was identified from the content of POC and MAOC and their proportion to total SOC.Redundancy analysis,multiple stepwise regression,structural equation model and other methods were used to analyze the influence and difference of soil physical,chemical and biological properties on organic carbon and its components POC and MAOC,and identify the variation mechanism of organic carbon components,in order to provide scientific basis for agricultural development and soil quality improvement in the sediment affected area of the Yellow River.The main conclusions are as follows:(1)The carbon composition of the soil in the study area has poor stability and is prone to change under human interference.In the 0-40 cm soil layer,the content of soil organic carbon,POC,and MAOC ranges from 1.53 to 24.99 g/kg,0.87 to 23.33 g/kg,and 0.19 to 5.96 g/kg,respectively.POC is the main component of SOC,and in the 0-20 cm soil layer,the proportions of POC and MAOC in SOC are 85.3% and 12.9%,respectively;In a soil layer of 20-40 cm,the proportions of POC and MAOC in SOC are 80.9% and 19.1%,respectively.Overall,the content of SOC,POC,and MAOC in the 0-20 cm soil layer is higher than that in the 20-40 cm soil layer.There is no significant difference in the coefficient of variation between the upper and lower layers,but there is a significant difference in the proportion of content between the upper and lower layers.From the content and contribution ratio of POC and MAOC,it can be seen that the soil organic carbon components in the study area have poor stability,easy conversion,and active properties.(2)Land use and planting patterns have a significant impact on improving soil organic carbon and its components(POC,MAOC),and are important driving factors for improving soil organic carbon stability.Agricultural cultivation is beneficial for increasing the stability of soil organic carbon.In the 0-20 cm soil layer,the content of SOC,POC,and MAOC in different land use types is as follows: cultivated land>garden land>forest land.In the 20-40 cm soil layer,the content is as follows: cultivated land>forest land>garden land,and in the profile,the surface layer is greater than the deep layer.In the 0-20 cm soil layer,the distribution proportion of POC in cultivated land is lower than that in forest land and garden land,with 85%,87%,and 87%,respectively,while MAOC is the opposite,with 15%,13%,and 13%,respectively;In the 20-40 cm soil layer,the distribution proportion of POC in cultivated land,forest land,and garden decreased by79%,76%,and 82%,respectively,while the proportion of MAOC increased by 21%,24%,and 18%,respectively.Featured planting significantly promotes the accumulation of inert organic carbon components in soil,reduces the content of active carbon components,and is conducive to improving the stability of deep soil organic carbon.In the 0-20 cm soil layer,the content of SOC,POC,and MAOC showed a significant increase in characteristic planting compared to traditional planting.MAOC accounted for 15% and 16% of SOC in characteristic planting and traditional planting,respectively.In the 20-40 cm soil layer,the content of SOC and POC showed a significant increase in characteristic planting compared to traditional planting,while MAOC showed the opposite.MAOC accounted for 23% and 16% of SOC in characteristic planting and traditional planting,respectively.(3)The physical,chemical,and biological properties of soil are important factors affecting organic carbon and its components.From the relationship between soil physical,chemical,and biological properties and SOC,POC,and MAOC,in a 0-20 cm soil layer,SOC,POC,MAOC and MBC,MBN,urease,sucrase,phosphatase,TN,moisture content,clay(<2 μ m)Fine powder particles(2-5 μ m)Medium powder particles(5-10 μ m)There is a significant positive correlation(P<0.01)with p H and fine sand particles(50-250 μ m)Coarse sand particles(250-500 μ m)There was a significant negative correlation(P<0.01)with BD,catalase,and gravel(1000-2000)μ m)The correlation is not significant.SOC,MAOC,and Coarse Powder(10-50 μm)Significantly positively correlated with coarse sand particles(500-1000 μ m)There is a significant negative correlation between POC and coarse powder particles(10-50 μ m)Coarse sand particles(500-1000μ m)The correlation is not significant.Compared to the surface layer(0-20 cm),the correlation between soil physical,chemical,and biological properties and SOC,POC,and MAOC in the deep layer(20-40 cm)is weak.(4)Based on methods such as redundancy analysis and structural equations,comprehensively quantify the contributions and impacts of various influencing factors on organic carbon and its components.The results showed that soil physical,chemical,and biological properties had impact on SOC,POC,and MAOC.However,the contribution ratios of soil physical,chemical,and biological properties to organic carbon and its components vary.Chemical properties contribute the most to POC(0.75)and SOC(0.74),while biological properties contribute the most to MAOC(0.34).The fitting degree between SOC,POC and soil physical,chemical,and biological properties is higher than that of MAOC.