Studies On Establishment Of Soil Series In Chinese Soil Taxonomy In Central Sichuan Hilly Region

Soil is an important environmental resource for human living and production activities.The classification of soils can reflect the law of occurrence and evolution about soils,and contact and distinguish the type of soil,then provide basis for human using soil resource scientifically.Development with the science,the genetic classification of soil is gradually changing to taxonomy,qualitative indicators of soil gradually change to quantitative indicators.At the sametime,Chinese soil taxonomy is increasingly sound.As the basic classification unit of soil taxonomy,soil series can directly reflect the occurrence characteristics of soil in senior classification unit,At the same time,soil series can be closely linked with production activities.Central Sichuan hilly region is the important Crop-producing area,but the study of soil series division started late and carried out little.27pedons in central Sichuan hilly region were selected as research objects,the environment conditions,profile characteristics and physical and chemical properties of soils in the area were studied.According to the diagnostic horizons and diagnostic characterstics of Chinese soil taxonomy,divided the corresponding soil series.The main conclusions are as follows:?1?Regional climate is subtropical monsoon humid climate,rain and heat over the same period,landform is dominated by hills,the relative elevation difference is small,climate varies slightly in the vertical direction.Soil parent material are mainly residual matters and slope deposits of Shaximiao formation,Penglaizhen formation,Suining formation and Cangxi formation,sediments of pleistocene series also exist.The land use type are dry land and forest land.In addition to seasonal crops,surface vegetation also includes the Poaceae Barnhart,Coriariaceae,Cupressaceae and Myrtaceae.Regional soil types are abundant,which are more influenced by human factors.?2?The value and chroma of soils in the study area were rich,the hue span was large.Soil structure were dominated angular blocky structure and subangular blocky structure,while soil texture was mostly loam.The pH of soils was related to soil parent material,acidic,neutral and calcareous soils were available,at the same time,CaCO₃ content in soils was proportional to pH.Soil organic carbon and total nitrogen content were low.The soils with yellowish hue had more free iron content and higher iron dissociation.The base saturation in soil was proportional to pH,but total exchangeable acids was weak in acidic soil.?3?Diagnostic surface horizons in Central Sichuan hilly region included Mollic epipedon,Ochric epipedon.Diagnostic subsurface horizons included Cambic horizon,Argic horizon.Diagnostic characteristics included L.C.of purplish sandstones and shales,Lithic contact,Paralithic contact,Udic soil moisture regime,Redox features,Thermic soil temperature regime,Ferric property and Calcaric property.Diagnostic evidence was Alic evidence.?4?Order in Central Sichuan hilly region included Argosols,Cambosols and Primosolos.Suborders were 7,included Udic Argosols,etc.Groups were 8,included Acidi-Udic Argosols,etc.Subgroups were 13,included Ferric Acidi-Udic Argosols,etc.According the size of particles,mineral composition,pH and soil temperature,there were 19 Families in the study area.Chossing the depth and thickness of characteristic layers,texture of the surface soil,soil color and stratigraphic unit of parent material as the basis of Soil Series,the soils were ruled into 26 series.