Soil Carbon Fraction And Stability Of Paddy Field From Different Origin Types

Soil is one of the major carbon pools.Small changes of soil organic carbon pool will have a profound impact on the dynamic balance of the global carbon cycle.In particular,the impact of agro-ecosystems on the global carbon cycle and climate change should not be underestimated.Paddy soil is a unique soil type characterized by high organic carbon content and high potential for carbon sequestration.China is the world’s largest producer of rice.The paddy soil has a variety of parent materials that profoundly affect the holding capacity and stability of soil carbon.Studying the characteristics of carbon stocks and their stable mechanisms in paddy soils of different development types have important theoretical and practical values for mitigating climate change and achieving sustainable agricultural production.Based on this,this study selects paddy soils of different developmental types as the research object.On the basis of field surveys,field sampling and laboratory analysis,qualitative analysis and quantitative analysis,theoretical analysis and field testing are combined.Through physical and chemical grouping methods,with the aid of nuclear magnetic resonance technology and modern molecular biology techniques,the physical,chemical,and microbiological mechanisms for the determination of active organic carbon components and their stability in soil carbon pools were determined and analyzed.The main findings are as follows:(1)The contents of total organic carbon(SOC),dissolved organic carbon(DOC),easily oxidized organic carbon(EOC),microbial biomass carbon(MBC)and light organic carbon(LFOC)in different development types of paddy soil were respectively 6.24 g/kg-46.8 g/kg,37.9-118 mg/kg,3.65 g/kg-22.5 g/kg,40.4 mg/kg-257 mg/kg,and 3.68 g/kg-10.1 g/kg.Moisture content,pH,ammonium nitrogen,nitrate nitrogen,available phosphorus(AP),total phosphorus(TP),soil mechanical composition and other factors are the key factors affecting the composition of soil organic carbon pools.(2)The brick-red soil type paddy soil has the highest content of 1-0.5mm water-stable aggregates,while other development types of paddy soils have the highest content of<0.25mm grain-sized water-stable aggregates.In black soil,purple soil and saline-alkaline soil,the organic carbon of 1-2 mm particle size contributes the most to soil organic carbon;red soil and brick-red soil type of paddy soils have the largest contribution rate to soil organic carbon with<0.25 mm particle size aggregates.(3)The dominant chemical bonding stable morphology of paddy soils of different developmental types is iron-aluminum bonded organic carbon.The to(alkyl carbon)/co(alkoxy carbon)and ω(hydrophobic carbon)/ω(hydrophilic carbon)indicators revealed that the organic carbon chemical molecular structure of paddy soils developed from red soil is more stable.(4)The composition of microbial communities in paddy soils of different developmental types differs significantly.Soil type is one of the major factors affecting the structure and diversity of microbial communities.Soil microorganisms have a certain influence on the stability of organic carbon.The higher the ratio of soil fungal bacteria,the higher the soil organic carbon activity.The ratio of fungal bacteria in paddy soils with different developmental types is:red soil type paddy soil<saline-alkaline soil paddy soil<brick-red soil type paddy soil<black soil paddy soil<purple soil paddy soil.(5)The ratios of active organic carbon to total organic carbon in different developmental types of paddy soil were consistent.The results of EOC/SOC ratio and soil organic carbon activity reveal that organic carbon in black soil is more stable.The organic carbon content of<0.25mm aggregates and the content of Fe-Al-BOCs in the soil were the main factors affecting the SOC stability in different developmental types of paddy soils.