Research On Soil Characteristics And Taxonomic Classification At Huoditang Forest Region In The Qinling Mountains

Qinling Mountain is the important boundary geography and environment between the south and north part of China. The natural landscape varys regularly and gradually in verticality. The various mountain climate, biology, landform and parent material lead to numerous soil types and different distribution of soils in verticality. Eleven typical profiles of different altitude in Huoditang Forest Region were researched in this study. By field survey, the physical and chemical characteristics analysis of the soils, we studied thoroughly the soil genetic, discussed the positions in Taxonomic classification and the distribution of the soils on the basis of the Keys to Chinese Soil Taxonomy(3rd edition), and to provide the foundation of Soil Taxonomy of mountain and resources development. The results indicate that:1.The main physical and chemical characteristics vary regularly: with the rising of the altitude, there is a transition from silt> sand> clay to the sand> silt> clay in the mechanical composition; the Argic horizon emerges below the altitude of 1300 meters; the content of organic matter is enrichment, the content of organic carbon of epipedon is higher than 20 g/kg, while the content of organic carbon increases with the increasing of altitude, and in the altitude of 2100～2500 meters of Gleysols, the soils have the maximum content organic carbon; the soils appear acid or acid-slightly reaction, the pH decreases appreciably and acid strengthen with the increasing of altitude; the soils higher than the altitude of 2400 meters are base unsaturated, indicating the soil leaching is strong, the pH and BS are distinct plus correlated; the contents of SiO₂, Al₂O₃ and Fe₂O₃ of the soil body and clay are all relatively stabilization; in the soil body, the content of SiO₂ is much higher and CaO is very little, the total contents of SiO₂, Al₂O₃ and Fe₂O₃ occuppy 90% of the mineral parts, the sequence of mineral elements is: SiO₂> Al₂O₃> Fe₂O₃> K₂O> MgO> CaO> TiO₂> MnO.2. The diagnostic surface horizons divided on the soils of the areas are Mollic epipedon and Ochric epipedon. The diagnostic subsurface horizons are Cambic horizon, Argic horizon and Gley horizon, Histic evidence and mattic evidence. The diagnostic characteristics are Sapric soil materials, Folic soil materials, Soil moisture regimes, Soil temperature regimes and Base saturation. 3. The soil are divided into three soil Orders, three Suborders, four Groups in Soil Taxonomy; the vertical structure in Huoditang: Tipic-Hapli-Udic Argosols(<l300m)→Tipic-Hapli-Udic Cambosols(1300～2200m)→Tipic-Hapli-Stagnic Gleysols(2100～2500m local distribution)→Molli-Hapli-Udic Cambosols (2200～2400m)→Acidi-Bori-Udic Cambosols+Molli-Bori-Udic Cambosols (above 2400m).4. Above the sea level of 2100 2500m in Pingheliang and great meadow area, there is local distribution of Gleysols, because of a long period of stagnant water, it occurs a strong vivo redox reaction in the soil, the color of gley horizon is gray to white, so the soil of this area is Gleysols.5. Soil Taxonomy and Jenetic Classification results are basically consistent with each other, and distribution lines are broadly consistent with each other, that means taxonomy is based on the theory of soil genesis, the two classification systems are closely linked. However, in practical application process, the classification shows great importance to bio-climatic conditions, ignoring the time factor, and emphasizes the central concept, fuzzying boundary definition, diagnostic indexes are difficult to quantify, compared to Genetic Classification, soil taxonomy shows the higher superiority.6. Soil classification is a very complex, highly detailed and systematic work, the current study has laid a system of soil taxonomy framework and indicator system, but the specific indicators and the retrieval systems still need practical application in various places to be constantly revised and improved in various places.