Research On Soil Genetic Characteristics And Taxonomy Of Soil In Mao'er Mountain,Guangxi Zhuang Autonomous Region

Soil genetic characteristics and taxonomy of soil are the fundament of understanding soil,soil resource investigation,mapping and assessment.For now,quantification,standardization and unitization for thses are the general direction of the international development of soil taxonomy.In this study,the morphological features of ten typical soil profiles,which were sampled at different altitudes in Mao'cr Mountain,Guangxi Zhuang Autonomous Region,were analyzed through laboratorial analyses of soil physical and chemical properties.According to the criterion of<Chinese Soil Taxonomy?the third edition?>,the diagnostic horizons and the diagnostic properties of these soil profiles were assessed and the higher categories of soil types were classified.The results showed as follows:1 The soil sampled iin Maoer Mountain showed the obvious difference within profiles.It was composed by small lumps.Yellow-brown and yellow-orange were the main colors of the soil and the color of surface soil was the darkest for each of the profiles.With the increasing of altitude,the soil color became darker.The rank of the mechanical composition for each profile in decreasing order was sand,silt and clay.The loam was the main soil texture.The M8 profile had an argic horizon.2 There was abundant organic matter in the soil and it increased with the increasing of altitude.The organic carbon of soil was over 21g/kg at surface.The Al ion was the main cause of acidity of soil.With the increasing of altitude,the soil became more acid.The soil salinity was unsaturated and the leaching effect was strong.The quantity of Fet,Fed,and Feo in low altitude area was higher than that in high altitude area but the Fep was the opposite.The quantity of Fet,Fed,and Feo in the B layer was the highest for each of the profiles and the quantity of Fed in clay were significantly higher than the quantity in soil,indicating a tendency of the iron oxide to be enriched in the clay.With the increasing of altitude,the degree of soil fr-ee,the activation and the complexing went up but the hydration coefficient went down.3 SiO₂,Al₂O₃ and Fe₂O₃ were the main and stable molecular compositions of the soil.The rank of compositions in decreasing order was SiO₂,Al₂O₃,Fe₂O₃,K₂O,MgO,TiO₂,Na₂O,CaO,P₂O₅ and MnO.The quantity of SiO₂,K₂O and CaO in the clay was significantly lower than the quantity in the soil but the quantity of others was the opposite somehow.By calculating the change rate of elements,it was obvious that the constant elements have migrated in different degrees.The molecular ratio of soil was high and the differences among molecular ratios in the different profiles were not significant.With the increasing of altitude,the quantity of sanshui diaspore went down obviously and the kaolinite went down slightly but the quartz and illite went up.The main clay mineral in the soil changed from sanshui diaspore to kaolinite and quartz,resulting that the quantity of the 1:1 type mineral content went down and the 2:1 type mineral went up.4 The soils in this area had two diagnostic surface horizons?ochric epipedon and umbric epipedon?,three diagnostic subsurface horizons?cambic horizon,argic horizon and LAC-ferric horizon?and 7 diagnostic characteristics?soil moisture regimes,soil temperature regimes,humus property,ferric property,rich-aluminum characteristics,alic phenomenon and base saturation?.The soils in this study were classified into two soil orders,thr-ee suborders,three groups,three subgroups,six families,ten systems in Chinese Soil Taxonomy.