Genetic Characteristics And Taxonomy Of Soils In Mountain Areas Around The Sichuan Basin

Soil taxonomy is the mainstream of international soil taxonomy.A large-scale soil system classification research had been started in China in order to improve the classification system of soil system in China,with the support of the national basic scientific and technological work special project"Chinese soil".In this study,the soil in the middle and low mountain areas around the Sichuan Basin was selected as the research object.In this paper,the characteristics of soil genesis under subtropical humid monsoon climate and under the combined action of various complex soil-forming factors were studied,and the tested soils were systematically classified into soil series.The aim was to improve the classification of soil systems in Sichuan Province and lay the foundation for future systematic classification studies in the region.Below are key research findings:（1）There are various types of soil parent material in the mountainous areas around the basin,with slope deposits and debris,followed by alluvium,alluvial material.There are many types of colors involved in soil,and 10YR is the most common tone with a wide range of brightness and chroma.The main types of soil structure are massive,accounting for more than 85%of the total.Corner block and sub-corner block are the main types of block.Soil new formations were is most common with clay film,humic film and rust markings.Among the 42 soil profiles,15 soil profiles have lime reaction,mostly with mild strength.Most of the soil has a gravel content of less than 2%or not,and the soil texture type is mainly loam.The distribution of soil organic carbon and total nitrogen in the profile decreased irregularly with the increase of depth.Soil salt-based ion composition was Ca²⁺>Mg²⁺>K⁺>Na⁺,Al³⁺in the exchangeable acid are substantially higher than H⁺.（2）The soil in the mountainous area around the basin mainly contains the following diagnostic layers and diagnostic characteristics:four diagnostic subsurface horizons were Albic horizon,Cambic horizon,LAC-ferric horizon and Argic horizon;eight diagnosis characteristics were Lithologic characters,Lithic characters,Soil moisture regimes,Redoxic features,Soil temperature regimes,Ferric property,Allitic property and Calcaric property。（3）According to the system classification standard provided by CST,it is determined that the soil in the mountainous area around the basin has four orders,eight suborders,eighteen groups and twenty-five subgroups.According to the classification criteria of soil families,forty-one soil families were divided and established.Six indices,including landscape location,absolute content difference of new organisms,surface soil texture,parent material,soil color and soil thickness,were selected as the identification criteria for soil series,and forty-two series were further divided.