Study On Several Types Of Soil Characteristics And Soil Taxonomy In Southwest China

The paper aims at the research on Stagnic Anthrosols that are widely distributed in southwest China,Ustic Ferrosols,the basement soil of Yunnan dry-hot valley,and Ustic Vertisols,a highly special sort of soil found in Yuanmou.Guided by the principle of the classification of Chinese soils,it conducts the indoor analysis of the basic soil characteristics,especially the characteristics of Soil micromorphology and Dynamic Characteristic of Water Stability of Soil Structure through design sample piont,detailed inspection of soil,and environmental investigation.Besides,it also discusses the fundamental features of the three kinds of soils and the Diagnostic horizons,Diagnostic characteristics that are used to classify them.Based on the research,this thesis carries out a classified retrieval of the three kinds of soils and puts forward two tentative suggestions to《Keys to Chinese Soil Taxonomy》(3^rd edition).The research results are presented as follows:(1)The basic characteristics of the three kinds of soils are as follows.In terms of the constitution of the particles,the content of sand,silt and clay comparatively equals each other;Sand plays a dominant role in the constitution of the particles in Ustic Ferrosols, while the particles found in Ustic Vertosols are mainly clay.As far as soil pH is concerned, the profile of Stagnic Anthrosols largely presents neutrality to acid with a small part alkaline,and the pH value rises as the depth of the soil gets deeper;Ustic Vertosols generally was alkaline,and its pH value changes in the same tendency as that of Stagnic Anthrosols.The surface soil of Ustic Ferrosols is acidic,and the soil becomes less acidic and neutral.With respect to the content of organic matters,the highest percentage of it is found in Stagnic Anthrosols,which is normally above 15g/kg,the second highest percentage of it is detected in Ustic Ferrosols while the lowest percentage of content of organic matters,which is lower than 7g/kg,is found in Ustic Vertosols due to the influence of sparse forestation and invasion.As for soil CEC,it is contained in Stagnic Anthrosols in high quantities,except the two profile of YD 12and YD 13 soil extracted fi'om Dali,Yunnan; CEC in Ustic Vertosols shows a less percentage and in Ustic Ferrosols,it is largely found in the A1 layer but not in the B_w layer.(2) Correlation analysis on the soil characteristics and the content of the water stability soil structure showed that the content of the water stability soil structure was closely related to capillary porosity,silt content and clay content of the soil in the first 3 hours,and after then their correlation began to decrease.Especially,during the second hour, an extremely positive correlation was observed between the water stability soil structure content and soil capillary porosity,and the correlation coefficient was 0.855,which showed that the higher the soil capillary porosity,the greater the soil water stability structure content,water stability soil structure content had a highly negative correlation with silt content,and their correlation coefficient was -0.759;and it had a highly positive correlation with cosmid content,and their correlation coefficient was 0.635.It was proved that silt had dispersal property and the cosmid was provided with constipate,so that they had different impacts on the soil water stability structure.There were no obvious correlations between the water stability of the soil structure and the other soil characteristics such as organic content and pH of the soil,etc.(3) It can be explained clearly by Soil micromorphology and X-ray diffraction analysis.Ustic Ferrosolscontains rich soil skeleton grain,most of which is Quartz.Main part of fine-grained material of the soil is humus—clay matrix.Soil formations mainly contain iron particles.The main characteristic of the soil's micro-structure is void.Ustic Vertisols contains little skeleton grain,and it mainly contains Quartz.The main component of soil plasmic material is calcic clay matrix.Soil formations contain more calcite formations particle and a lot of microcrystalline calcite and optical clay.The soil's micro-structure is mainly divided into fissure.The content of clay and sand-silt is quite high.Cementation action of calcic-clay matrix is weak.While the clay described above mainly contains expansibility clay mineral,whose expansion and contraction is strong. Furthermore,expansibility clay mineral has a particular erosion process.Therefore,under the weather with alternation dry and hot for a long period,it is easy to form rich cracks in soil body,and form block structure,prism- block structure and all kinds of void between them.Most skeleton grain of Stagnic Anthrosols is mineral particle and fine quartz particle. The main part of fine matrix is clay matrix.Most of soil formations is iron-clay matrix, iron-manganese speckle and concretion,iron coating,and part of profile contains humus formations and calcium carbonate formations.Main formation of The soil micro-structure is block structure,prism- block structure and plate structure,and part of profile is flocculate structure and presents different microorganism mycelium characteristics.Fissure and linear structure void can be seen in profile YS0709 with various characteristics.(4) The ten typical profile have been classified into the three Order:Ferrosols,Vertosols and Anthrosols,three Suborder:Ustic Ferrosols,Ustic Vertisols and Stagnic Anthrosols,six soil Group:Hapli-Ustic Ferrosols,Hapli-Ustic Vertisols,Fe-leachic Stagnic Anthrosols,Fe-accumulicStagnic Anthrosols,TypicStagnic Anthrosols and Hapli-Stagnic Anthrosols,and seven soil Subgroup:Trunic Hapli-Ustic Ferrosols,Trunic Hapli-Ustic Vertisols,Typic Fe-leachic Stagnic Anthrosols,Typic Fe-accumulic Stagnic Anthrosols,Purpli-TypicStagnic Anthrosols,Typic Hapli-Stagnic Anthrosols and VerticHapli-Stagnic Anthrosols.(5) The classification of soil system is a complicated,dedicate,yet systematic work. There have been researches that have laid the foundation on the systematic framework of the soil classification in China,but the index of classification and retrieval system still need to be amended and supplemented in the actual practices in various places.Through the comparison between the research results and the definition given in《Keys to Chinese Soil Taxonomy》(3^rd edition).Conceming Diagnostic characteristics,the following implications are made tentatively:①Invasion is a characteristic that is of much significance in the process of soil formation in Ustic Ferrosols and Ustic Vertisols distributed in Ganre River Valley in Yuanmou,Yunnan.The author wonders if it is possible that the invasive ability of the soil could be further classified to function as a Diagnostic characters according to the research method for Dynamic Characteristic of Water Stability of Soil Structure designed in this thesis.②Stagnic Anthrosols usually develops from long period of oxidation-reduction reaction and profound manmade influence.The Stagnic Anthrosols being researched in this thesis has been long cultivated thus possesses good structural development.Through Soil micromorphology,a special phenomenon could be observed that there are large amount of iron-manganese speckle and concretion,humus formations,calcium carbonate formations flocculate structure and presents different microorganism mycelium characteristics existed in Stagnic Anthrosols.Is there any chance that we use the Soil micromorphology that is comparatively special in Stagnic Anthrosols as a supporting identifying toll in the retrieval of this category of soil so that the developing status could be reflected?...