| Soil type is the comprehensive expression of external soil forming conditions and internal soil attributes.Its spatial differentiation is the result of landscape factors such as soil forming parent material,water status and biological conditions changing with time and space.The landscape types in karst mountainous areas are complex and the soil types are diverse,but there is still a lack of systematic and quantitative research on the relationship between soil type differentiation and landscape change in this area.Therefore,this paper takes Houzhaihe small watershed in Puding County,Guizhou Province as the research area.Firstly,based on the comprehensive analysis of the regional soil forming environment,the karst landscape types are divided according to the principles and methods of landscape ecological classification,and the landscape type reference method is used to complete the layout of representative soil profile points in the typical "landscape facies" with reference to the standard of China soil survey technology.Secondly,according to the principles and methods of soil systematic classification in China,the diagnostic layer and diagnostic characteristics of representative profiles are determined,and the high-level taxon and grass-roots taxon are divided on this basis.Finally,by analyzing the relationship between different landscape factors and soil diagnostic layer,diagnostic characteristics and type development,this paper discusses the indicative effect of landscape change on soil type differentiation.The main results are as follows:(1)Geomorphology,land use type,soil forming parent material and positive and negative topography are selected as the dominant landscape factors affecting soil development in the study area,and the functional morphology method and decision tree classification method are adopted,From top to bottom,the study area is divided into 9 "landscape areas"(upstream peak forest depression,old peak forest funnel depression,peak cluster Valley,peak forest funnel depression,midstream peak forest basin,midstream peak forest depression,revived peak forest basin,peak forest laterite platform and downstream peak forest basin),53 "landscape categories",78 "landscape subclasses" and 94 "landscape facies".(2)According to the scale standard of 1:100000 in China soil survey technology,the study area belongs to class IV terrain,that is,the area represented by each section point is 1.5km2.Except for the area occupied by buildings,water areas and bare land that do not need to be arranged,43 typical soil sections need to be arranged in this area;Based on the comprehensive analysis of the typicality and representativeness of "landscape facies",combined with 1.07 M google satellite image,43 typical sections arranged by using "landscape type reference method" cover most of the soil types in the study area,and the boundary of landscape facies also provides a reference for the search of soil type boundary.(3)According to the retrieval of Chinese soil systematic classification(the Third Edition),a total of 4 diagnostic surface layers(thin surface layer,dark fertile surface layer,hydroponic surface layer and dark barren surface layer)were determined from 43 typical profiles,The lower layer of 5diagnostic tables(hydroponic redox layer,rudiment layer,bleaching layer,low activity iron rich layer and clay layer)and 10 diagnostic characteristics(lithology characteristics of carbonate rock,humus characteristics,incubation characteristics,average humus characteristics,iron characteristics,aluminum rich characteristics,redox characteristics,stone contact surface,soil moisture and temperature conditions).6 soil classes(leached soil,iron rich soil,rudiment soil,newly formed soil,homogeneous soil and man-made soil),8 subclasses,14 soil classes and 19 subclasses were retrieved;Finally,with reference to the standard for the division of soil groups and soil series in China's soil systematic classification,combined with the field investigation and the reality of soil development characteristics,the test soil samples are divided into 37 soil groups and 42 soil series.(4)In Houzhaihe watershed of Puding County,Guizhou Province,different landscape factors and their combinations can play a certain role in indicating the spatial differentiation of soil types.In the normal topography of Fenglin basin in the middle reaches and Fenglin laterite platform in the lower reaches,the Quaternary red clay parent material is mostly developed into iron rich soil.In the forest and grassland landscape with small slope and weak surface erosion process,it is easy to develop into eluvial soil with obvious texture differentiation.In the funnel depression of the old peak forest of pure limestone in the upper reaches,the soil undergoes oxidation-reduction due to wet water conditions and develops into light colored moist prototype soil,while in the slope waist of the peak forest and peak cluster whose parent material is dolomite in the upper and middle reaches,it mostly develops into calcareous moist prototype soil.The normal neodiagenetic soil layer is shallow and has the characteristics of carbonate rock lithology,which is mainly distributed in the steep slope waist or the slope foot with serious exposed bedrock in the middle reaches of Fenglin basin and the downstream Fenglin laterite platform.In the positive terrain forest grassland landscape of the upper peak forest depression and peak cluster Valley,the soil developed from pure limestone is mostly lithologic homogeneous rotten soil,while in the abandoned land or dry land landscape of the negative terrain in the upper and middle reaches,the soil is saturated with water for a long time and has redox characteristics,and mostly develops into moist homogeneous rotten soil with iron and manganese stripes.In the negative terrain paddy field landscape,soil development has experienced different degrees of hydroponic ripening,oxidation-reduction alternation,material leaching and deposition,thus forming hydroponic artificial soil with different properties and different degrees of development. |
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