Study On Occurrence Characteristics And Systematic Classification Of Typical Lime Soil In Limestone Outcropping Area Of Guizhou Province

The unique landform and diverse climate in the limestone exposed area of Guizhou Province provide complex natural environmental conditions for the formation and development of lime soil.The properties of lime soil in different regions have great spatial differences.As a key element in the fields of resource utilization,environmental governance and ecological restoration in karst areas of Guizhou Province,the systematic and quantitative research on its formation,development and classification is still insufficient.Based on the soil forming environment and distribution characteristics of carbonate soil,this paper takes 44 typical lime soil profiles in limestone exposed areas of Guizhou Province as the research object,and analyzes the occurrence characteristics of typical lime soil and its relationship with soil forming environment through field fixed-point investigation,investigation of soil forming factors,division of profile levels and observation of morphology,collection of samples and indoor physical and chemical experiments,Determine its attribution in soil genetic classification in China;According to the methods and principles of soil systematic classification in China,the diagnostic layer and diagnostic characteristics of the tested soil are determined.Based on this,the highlevel taxon retrieval and grass-roots taxon division are carried out.Finally,the soil systematic classification results are compared with the occurrence classification.The results are as follows:(1)There are obvious differences between the dry and moist colors of typical lime soil in limestone exposed areas of Guizhou Province.The dry colors are mainly dark brown(7.5YR 3 / 4)and turbid yellow brown(10YR5 / 3),and the moist colors are mainly black brown(10YR 3 / 2 and 7.5YR2 / 2)and turbid yellow brown(10YR 4 / 3).The soil thickness of lime soil profile varies greatly(15-120cm),and the soil configuration is mainly AB-C and A-B-R.The accumulation of humus was obvious(the content of surface organic carbon was 46.29 ± 30.04 g / kg),and the content of organic carbon decreased with the increase of depth.The texture types are mostly clay and silty clay.During the formation and development of calcareous soil,the leached base in the soil is continuously supplemented through biological calcium recovery,humus calcium coagulation and karst water supply.The base saturation is high(71.87 ± 14.62%),the cation exchange capacity is also high(21.76 ± 11.76 cmol(+)/ kg),and the soil is mostly neutral(p H 7.15 ± 0.75).At the same time,the free iron oxide in the soil is at a high level(45.77 ± 16.97 g / kg),and the degree of soil weathering is high.Under the same climate type,slope position and land use mode have an impact on soil development.Under the same land use mode slope position,climate will affect soil differentiation.(2)According to the theory and method of soil genesis classification in China,44 typical soil profiles in limestone exposed areas of Guizhou Province belong to primary soil class,stone primary soil subclass and calcareous soil class,which can be divided into 4 subclasses,5 soil genera and 10 soil species,including red calcareous soil,yellow calcareous soil,Brown calcareous soil and black calcareous soil.(3)Based on the retrieval of Chinese soil system classification(the Third Edition),three diagnostic surface layers,three diagnostic table lower layers and eight diagnostic characteristics were determined from 44 typical profiles in limestone exposed areas of Guizhou Province.Five soil classes,eight subclasses,nine soil classes and 15 subclasses were retrieved,including eluvial soil,iron rich soil,rudiment soil,humus soil and newly formed soil.Based on the principle of the standard for the classification of soil groups and soil series in China's soil systematic classification,combined with field investigation and soil development characteristics,35 soil groups and 43 soil series can be established.(4)The approximate comparison between the typical calcareous soil in the limestone exposed area of Guizhou Province and the five soil classes of China's soil systematic classification shows that the classification results of China's soil systematic classification can accurately and quantitatively reflect the similarity and difference of soil properties under the complex soil forming environment in karst mountainous areas of Guizhou Province,which is conducive to the objective understanding of the differentiation of soil types.(5)There are great differences in the diagnostic characteristics of the soil in each typical section of black lithologic humus soil.It is suggested to add two subclasses under the category of black lithologic humus soil,namely humic black lithologic humus soil and viscous black lithologic humus soil.