Spatial And Temporal Variability And Sample Placement Of Reclaimed Soil Nutrients

Most open-pit coal mines are in arid and semi-arid ecologically fragile areas in our country,and it is very difficult to restore ecological restoration in mining areas.The distribution characteristics of soil nutrients directly affect the effect of land reclamation.At the same time,the study of spatial and temporal variability of soil nutrients can guide the sampling work and improve the pertinence and efficiency of sampling work.In this study,the dumping site in Pingshuo Open-pit Coal Mine was used as the research area.In 2013 and 2017,soil organic matter(SOM),soil total nitrogen(STN),soil available potassium(SAK)and soil available phosphorus(SAP)of surface soil were studied.For the research object,the spatial-temporal variability and its variation of soil nutrients in the early stage of reclamation were analyzed from different angles.The factors affecting the soil nutrient content and spatial distribution of reclaimed soil were analyzed and Explored the applicability of two methods for laying up soil samples.The following conclusions were obtained:(1)Compared with the results of 2013,the average content of SOM,STN,SAK and SAP increased by 36.15%,42.86%,42.89% and 48.99% respectively in the past four years.In 2013,the soil nutrient coefficient of variation,SAK>SAP>SOM>STN,ranged from 10.43% to 53.43%;in 2017,the soil nutrient coefficient of variation,SOM>SAP>SAK>STN ranged from 14.28% to 40.75%,all of which were moderately variable.(2)In addition to SOM,the spatial correlation of other soil nutrients increased with time;SOM has medium spatial correlation,spatial correlation of STN and SAP changed from medium to strong,and spatial correlation of SAK changed from weak to medium.It showed that structural factors had a greater impact on the spatial correlation of soil nutrients in the past four years.(3)There are significant differences in the spatial distribution and content change of different soi nutrients.After the dumping site has just been leveled,the SOM content distribution was not strong,but the STN and SAP distributions had obvious aggregation boundaries,and the SAK pattern was fragmented.The soil nutrients changed significantly before and after re-cultivation,and the distribution of soil nutrient changes was basically consistent with the distribution in 2017.(4)Different vegetation allocation patterns have different effects on soil nutrient.III(Hippophae rhamnoides×Calamagrostis epigejos)model has a greater impact on the improvement of SOM content,II(Medicago sativa)mode is conducive to the accumulation of STN and SAK,I(Buckwheat)And II(Medicago sativa)mode has obvious effect on SAP accumulation in the early stage of reclamation.The effects of topographic factors on soil nutrients were not all the same.(5)Compared with the traditional sampling method and the spatial stratified sampling method,the spatial random sampling method could well describe the spatial variability of soil nutrients in the study area,and the optimal sample size range of soil available phosphorus is 43-49;using conditional Latin hypercube sampling,50-55 was selected as the best sample size for the study area,which could well describe the environmental covariates that affect the soil nutrient content and its distribution in the study area.By qualitatively comparing spatial random sampling and conditional Latin hypercube sampling,conditional Latin hypercube sampling could be selected without prior data.