Properties And Taxonomy Of Soils Developed From Volcanic Ejecta In Changbai Mountains

This study takes soils developed from volcano extrusive of Changbai mountain, Longgang and Kuandian as research object, described the morphological characteristics of experimental soils, tested and analysised pH values, organic carbon, phosphate retention, iron-aluminium oxides and volcanic glass, discussed diagnostic horizons and diagnostic characteristics and carried out Taxonomy on the soil profiles according to principles and methods of Keys to Chinese Soil Taxonomy (3rd ed) and Keys to Soil Taxonomy(The USA11th ed). the results showed that:(1) The configuration of soils in Jinlong Dingzi and Tianchi are respectively A-BC-C and A-AC-C, there are no layer B of structure, but the middle and bottom of the above soils and the soils of Huangyi mountain,Qingyi mountain and Dachuantou in Kuandian have all developped layer B,the configuration of soil profiles are A-B-BC、A-B-C or A-B, furthermore, the soil texture is thinner than the top soils in Jinlong Dingzi and Tianchi, the soil development is higher.(2) The organic carbon content of selected soils are between0.53～108.80g kg-1, all belong to mineral soils.The pH(H2O) values of most soils in Jinlong Dingzi are between6.50～7.73, neutral; the pH(H2O) values of majority soils in Tianchi and Kuandian are less than6.5, acidic. In addition to top soil profile of Tianchi and A layer of other soil profiles,the pH(NaF) values of majority soils are greater than9.4. The phosphate retention capacity of each horizons in top and middle part of Tianchi are all less than25%, the vast majority of oher selected profiles are between25%～85%except some individual layers.(3) The tested soils all contain allophone and volcanic glass, the allophone content is betweem0.53%～16.46%; the volcanic glass content is between30.64%～69.28%, all exceed5%.(4) The top soils of Tianchi belong to Primosols,it is not have volcanic properties because of the very low phosphate retention capacity, the middle and bottom soils have respectively developed imto Cambosols and Andosols.The soils from volcanic cone of Jinlong Dingzi and Huangyi mountain in Kuandian are all with volcanic properties and classified as Andosols. Soils of Yizi mountain in Kuandian do not have volcanic properties because of grain composition between0.02～2mm is less than300g kg-1.The top, middle soils of Dachuantou mountain volcanic cone in Kuandian are all classified as Andosols, but the bottom part soil developed imto Cambosols.(5) Soils developped from volcanic ejecta are not necessarily Andosols. During soil genesis process,volcanic ejecta is devolopped as Primosols first,after that they form soil structural body along with the deepening of development degree,and then devolopped as Andosols or Cambosols;later accompanied by weathering enhanced, they also form soil types of higher degree of development. (6)The development degree of different part of volcanic cone is dissimilar, generally speaking, the development degree of the top soils from volcanic cone is waken, and the development degree of the middle and bottom soils is higher; the longer of soil genesis time,the higer of development degree.