Regional Landscape Classification For Soil Series Survey In The Plain Farmland Area

Chinese Soil Taxonomy(CST)has made great progress at present.Senior classification level of CST has been established.Our country is in the stage of researching on the standard of basic taxonomic unit classification.The technology of soil survey and mapping also has been obtained a series of research results,such as the soil survey technology for soil taxonomy-subgroups and the soil survey technology for soil taxonomy-soil series in hilly area.However,the soil series survey technology in plain farmland area is relatively rare and need to study further.Soil-landscape model is an important theoretical basis.To sum up,we realized and grasped the experience of landscape classification in a small area for soil series survey and mapping.Taking a region in the Zhou Gang,Nanjing,as a sample,we set up a series of classification principles and index for soil series in plain farmland area,and built landscape classification system referring to the theory of landscape ecological classification and the characteristics of soil series in the plain farmland area.Base on this,the land use,microtopography and crop growth were selected as the classification index,and the decision tree classification method was used to carry out the regional landscape mapping using spatial analysis tools of ArcGIS.Learned from the experience of traditional soil survey techniques,we took regional landscape classification systems and its map for a reference,carried out soil series survey with the help of the landscape variation and confirmed 12 soil series types.Finally,we analyzed soil types,soil properties and its distribution,in order to explore relationship between soil series and regional landscape.Main results of this study are as follows:(1)Landscape factors can point out the properties and distribution of soil series in the plainfarmland area,such as microtopography,land use,hydrological condition and crop growth etc.Landscape factors provide a reference for soil series survey and mapping,such as the locationof samples,route selection.Therefore,landscape phase can reflect the properties anddistribution of soil series in the plain farmland area.(2)Under different microtopography types,landscape factors that plays a leading role in the properties and distribution of soil series are different.Dominant landscape factors are parent material and the position of terrain in low hills.The region in terrace and highlands are parent material,land use and hydrological condition.The region in plain are hydrological condition and the texture of parent material.The region in lowlands is the location of groundwater.(3)The crop growth information can indirectly reflect the change of soil properties in plain area.Specific performance are as follows:In poor crop growth area,soil texture is clay loam,groundwater depth is low,the location of the gleyic horizon is shallow,and the change of free iron is small from top to bottom.In the medium crop growth area,soil texture is sandy loam,groundwater depth is low,and the change of free iron is little from top to bottom.In better crop growth area,soil texture is clay loam,groundwater depth is high,the location of the gleyic horizon is deep,and the change of free iron increase first and then decrease from top to bottom.Therefore,crop growth information,as an auxiliary factor,can distinguish the differences of regional landscape in a small area where the terrain is smooth and the land use is single.(4)The boundary of soil series is often at the place where the main landscape factors changes tempestuously.The transition characteristics at the boundary of soil series be attributed to the variation of main landscape factors.The greater the landscape changes,the more suddenly the transition characteristics at the boundary of soil series become.(5)When we carry out soil series survey and mapping using regional landscape,we should have a systematic and comprehensive understanding for the structure and function of regional landscape.The research process of regional landscape and soil series survey are simultaneous and mutually reinforcing.It helps to gain a better understanding of its characteristics and relationship.