Genetic Characteristics And Taxonomy Of Typical Soils In Karst Areas In Guizhou Province

The geomorphology,lithological characteristics and land use patterns of Guizhou karst area are complex and changeable,which have a significant impact on the formation and development of soil.Soil is an important basic element in the fields of resource utilization,environmental protection and ecological restoration in Guizhou karst areas.Many practical applications require a more systematic and quantitative study of the formation,development and classification of soil in this area.In this study,24 soil profiles in the small watershed of the Houzhai River in the Karst area of Guizhou Province were used as the research object.The soil formation environment and soil physical and chemical properties were analyzed through data collection,field sampling,and indoor physical and chemical experiments.Comparing the differences of soil occurrence characteristics under different soil forming environmental conditions.According to the methods and principles of Chinese soil system classification the diagnostic horizons,diagnostic characteristics and advanced classification units of the tested soil are retrieved and the soil family and soil series are classified.The soil taxonomic classification and the soil genetic classification are compared.The results of the study are as follows:(1)The soil moisture color is mainly turbid yellow brown(10YR4/3),black brown(10YR3/2,7.5YR3/2),brown(10YR4/4,7.5YR4/2,7.5YR4/4),bright brown(7.5YR5/6),gray-yellow-brown(10YR4/2),the color of dry soil is mainly turbid yellow-orange(10YR6/4),turbid yellow-brown(10YR5/3,10YR5/4),and the color gradually becomes lighter downwards from the surface.The texture type is mainly loam clay.Most of the sections have the A-B-C configuration.The part of the upper peak cluster depression valley and the estuary peak cluster valley depression in the limestone weathering part,there is no B layer developed,and the thickness is relatively thin(9?64cm);the p H under the above two types of landforms,CEC,clay CEC,exchangeable base,and base saturation are significantly higher than peak-forest Basin and peak-forest Platform,and the free iron oxide content are9.51?56.19g/kg and 20.45?49.06g/kg,which are significantly lower than peak-forest basin(32.12?57.68g/kg)and peak-forest platform(24.83?109.27g/kg).The quaternary red clay weathering material has a high degree of soil development,with an average thickness of more than1 m,and a clay content of 213.00?840.00g/kg,which is significantly higher than other soils developed by parent materials.The average silt-to-clay ratio is 0.66,which is significant lower than soils developed from other parent materials.The p H,CEC,clay CEC,exchangeable base and base saturation are significantly lower than those developed from other parent materials and the free iron oxide content is28.06?109.27g/kg,which is significantly higher than soils developed by other parent materials.Human activities mainly affect the formation and evolution of soil by changing land use methods.The weathering and leaching effect of soil in paddy fields is strong,and the CEC,base saturation are significantly lower than soil under other land use methods.Calcium and magnesium ions in the soil and anthrostagnic soil moisture regime caused by human cultivation will hinder the decomposition of organic carbon.The content of free iron oxide in the soil is significantly positively correlated with the content of clay particles.(2)According to "Keys to Chinese Soil Taxonomy(Third Edition)",the soil in the study area involves 4 diagnostic surface horizons: Mollic epipedon,Umbric epipedon,Ochric epipedon,Anthrostagnic epipedon and 4 diagnostic subsurface horizons: Cambic horizon,L A C-ferric horizon,Argic horizon,Hydroponic horizon,9 diagnostic characteristics:L.C.of carbonate rocks,Lithic contact surface,Soil moisture regimes,Soil temperature regimes,Gleyic features,Redox features,Isohumic property,Humus reserve ratio,Ferric property.(3)According to the "Keys to Chinese Soil Taxonomy(Third Edition)",a total of 6 soil Orders,7 suborders,12 soil groups,13subgroups: Typic Hapli-Stagnic Anthrosols,Typic Gleyi-Stagnic Anthrosols,Typic Fe-accumuli-Stagnic Anthrosols,Typic Black-Lithpmorphic Isohumosols,Typic Argi-Udic Isohumosols,Humic Hapli-Udic Ferrosols,Humic Argi-Udic Ferrosols,Humic Ferr-Udic Argosols,Typic Ferri-Udic Argosols,Humic Carbonati-Udic Argosols,Humic Carbonati-Udic Cambosols,Typic Ferri-Udic Cambosols,Carbonatic Udic-Orthic Primosols.(4)According to the "Criteria for Establishment of Soil Family and Soil Series in Chinese Taxonomy",combined with the field investigations in the study area,18 soil familes and 24 soil series are divided.(5)Comparing the occurrence classification of the tested soil with the systematic classification,the 5 suborders in the occurrence classification correspond to the 13 suborders in the system classification,among which the black lime soil mainly corresponds to the Carbonatic Udic-Orthic Primosols in the system classification.The corresponding types of yellow lime soil are relatively extensive,including Argosols,Cambosols,Isohumosols,etc.Yellow soil mainly corresponds to two subgroups of Humic Hapli-Udic Ferrosols and Humic Arg-Udic Ferrosols.The leaching paddy soil corresponds to Typic Gleyi-Stagnic Anthrosols,the infiltrating paddy soil corresponds to Typic Fe-accumuli-Stagnic Anthrosols and Typic Hapli-Stagnic Anthrosols,and the fertilizing paddy soil corresponds to Typic Hapli-Stagnic Anthrosols.It can be seen from the reference results that the soil system classification can distinguish more soil types.This quantitative classification system reduces the occurrence of different soils with the same name.Because there are certain differences between the two classification systems,the approximate reference made by the two often has a certain degree of complexity and uncertainty.