Study On The Mechanism Of Dynamic Change Of Aggregates And Organic Carbon In Reclaimed Mine Soils

The integrated application of organic amendments addition and mycorrhizal technology is a promising alternative to improve the degraded soil properties,and it has attracted much attention during the reclamation of mine soils.The study on mechanism of dynamic change of aggregates and soil organic carbon(SOC)in reclaimed mine soils is important for systematically analyzing the amelioration effect and carbon sequestration mechanism during reclamation.In this dissertation,based on data investigation and field trials,the action mechanisms of active sludge addition and arbuscular mycorrhizal fungi(AMF)inoculation on reclaimed mine substrates were analyzed.The key influencing factors of soil aggregates formation and stabilization mechanism during reclamation were studied by the path model.And the action mechanisms of growth and carbon sequestration of plant root systems on SOC accumulation were further discussed by minirhizotron technique.On the basis of above studies,the major conclusions are as follows:(1)The results of study on action mechanisms of sludge addition and AMF inoculation on reclaimed mined substrates were as follows.The soil physical,chemical and biological properties of FGS+ which was constructed by coal gangue(G),fly ash(F),sludge(S)and inoculated by AMF(+),were significantly better than FG,FG+ and FGS.The comparative analysis of reclaimed mine soil,reclaimed mine soil filled with fly ash and coal gangue and farmland soil revealed that,the content of SOC,total nitrogen(TN),available P were significantly improved after 6-year reclamation.The activities of invertase,acid phosphatase,alkaline phosphatase and dehydrogenase were also improved.In a whole,the practice of sludge addition and AMF inoculation can improve soil quality and promote the process of soil maturation,especially for SOC accumulation.(2)The results of study on formation process and stability evaluation of reclaimed mine soil aggregates were as follows.The aggregate fraction at the size of <0.25 mm comprised the largest proportion of soil aggregates in reclaimed mine substrates FG?FG+?FGS and FGS+ during 7-year reclamation,and the proportion decreased with reclamation age.The macro-aggregates(0.25~0.5mm,0.5~2mm and >2mm)proportion increased with reclamation age.These results indicated that the formation process of aggregates was that micro-aggregates integrated to macro-aggregates.The stability of soil aggregates enhanced with reclamation age.(3)The results of study on the key factors influencing soil aggregates formation were as follows.The aggregates fraction was significantly related to SOC by the unary dimension linear regression.The soil aggregates fraction(<0.25mm)was significantly related to SOC,available K,urease and easily extractable glomalin(EEG)by multi-variable linear regression return analysis.The path model revealed that the formation of soil aggregates contributed to SOC accumulation.While the EEG have indirect influence on soil aggregation by SOC.(4)The results of path analysis of SOC accumulation in reclaimed mine soils were as follows.The SOC in reclaimed mine soils were significantly related to 0.5~2mm fraction aggregates,invertase,alkaline phosphatase,EEG and root biomass in ryegrass by multi-variable linear regression return analysis.The analysis of path model revealed that the root biomass and 0.5~2mm fraction aggregates have the large total effect on SOC.The invertase activity has the largest positive effect on SOC,while the EEG had the indirect effect on SOC accumulation by 0.5~2mm fraction aggregates and invertase activity.(5)The results of study on action mechanism of ryegrass growth on SOC during reclamation were as follows.There were significant differences among SOC fraction in rhizosphere and bulk soil,which indicated that the root growth have significant effect on SOC The root density,the content of carbon in ryegrass roots and aboveground part,TG and EEG were closely related to the carbon fraction in rhizosphere and bulk soil,which showed that the root and GRSP has a positive effect on carbon sequestration.