| The serious surface subsidence caused by underground coal mining in high diving level area will lead to the irreversible change of soil structure,in which soil nutrients,soil carbon pool and soil enzyme activity will be affected.In recent years,filling reclamation has been widely used as a reclamation method in the treatment of coal mining subsidence land.Filling reclamation can effectively increase the storage of soil carbon pool,enzyme activity and nutrient content,however,there were significant differences in the storage of soil carbon pool,soil enzyme activities,spatial distribution of soil nutrients and restoration effects under different land filling and reclamation methods.In order to compare which filling and reclamation method is more effective to recover soil organic carbon in mining area,this paper takes sand filling,guest soil filling,lake mud filling and coal gangue filling as the research object in Jining,soil samples of 0-20 cm,20-40 cm and 40-60 cm of reclaimed land and its adjacent normal cultivated land were collected on site and laboratory tests were conducted,the spatial distribution and restoration of soil organic carbon,enzyme activities and nutrients in different reclaimed soils were studied.The results showed that:(1)The total organic carbon(TOC)in reclaimed soil has obvious surface accumulation,except for 0-20 cm Lake mud-filled reclaimed land,the SOC content of all soil layers in other reclaimed land is less than that of the control land,the restoration effect of four kinds of reclaimed soil SOC: Lake Mud Filling>guest soil filling>yellow river sand filling>coal gangue filling.(2)The proportion of organic carbon in different soil layers varied significantly(P<0.01),the proportion of HAC was the largest in 0-20 cm,the proportion of Doc was the largest in 20-60 cm,and the proportion of MBC was the smallest in all soil layers.Organic carbon fractions were significantly correlated with SOC,including EOC and HAC,LFC and POC,TOC,MBC,EOC,HAC,Doc and bulk density(P<0.01).In addition,MBC was the most sensitive to mud filling,EOC and Doc were the most sensitive to guest soil filling,LFC and POC were the most sensitive to coal gangue filling,and HAC was the most sensitive to yellow river sand filling.(3)The soil enzyme activity of reclaimed land is affected by different reclamation materials and shows different change law at different soil depths: the urease content of the sand reclaimed land of yellow river shows better "surface cohesion",the urease content of the reclaimed land filled with soil,lake mud and coal gangue decreased at first and then increased with the deepening of the soil layer,and the urease content of the soil in the surface layer recovered better than that in the soil layer,among them,the urease activity of Yellow River Sand,guest soil and coal gangue filled soil recovered in 0-40 cm soil layer or even exceeded its control,and the urease activity recovered best in 40-60 cm coal gangue filled soil,compared with the control area(34.21%),the restoration effect of the Yellow River sand reclamation land was the worst.The soil Catalase activity of the four filling and reclamation methods was worse at 0-60 cm than that of the control soil at 0-20 cm,which was affected by water content,except for Yellow River sand and coal gangue filling in 40-60 cm soil,the activity of soil Catalase recovered more than that of the control,the activity of other reclamation methods did not reach the Catalase level.The soil invertase activity in reclaimed land reflects the accumulation and transformation of soil organic carbon,and the invertase activity in the surface layer and the filling layer is higher than that in the control,however,the recovery of sucrase content in Yellow River sand and coal gangue was poor.(4)The results of nutrient content and enzyme activity of reclaimed soil were consistent with those of soil organic carbon and its components,except for Catalase,urease and sucrase activities were highly correlated with soil AN and AP;Soil Soc,Doc,MBC,ROOC and HAC were significantly and positively correlated with AN,AP,urease and sucrase,to some extent,the accumulation of soil organic carbon and its components are affected by each other,which is a process of dynamic cycling.(5)According to the analysis of the variation characteristics of soil organic carbon components in different reclamation methods,it was found that the reclamation of Yellow River Sand was beneficial to the restoration of HAC content,but the restoration effect of other carbon components was poor;Except for MBC,the recovery effect of other carbon components by filling and reclamation with coal gangue is not obvious,however,the restoration of LFC and Poc in 40-60 cm soil layer was promoted obviously.(6)The restoration effects of four reclamation methods on soil organic carbon and its components were summarized as follows: lake mud filling>guest soil filling>yellow river sand filling>coal gangue filling,it is suggested that the lake mud should be selected as filling material when filling and reclamation in this area. |
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