Soil Genetic Characteristics And Taxonomic Classification Of Beishan Forest Region In Qilian Mountains

The rich soil resource in Beishan forest region of Qilian Mountains plays an important role in supporting plant growth and improving the ecological environment.However,the study of soil taxonomy is lacking in the Beishan forest region,which restricted the exchange of scientific and technological information.In this paper,the soil pedogenic features under the vegetation types including alpine meadow,subalpine meadow,coniferous forest,broadleaf forest,and mixed forest were determined by investigating the morphological characteristics and analyzing,the soil physics-chemical properties and mineralogical characteristics.The diagnostic layer and diagnostic characteristics of soil were determined according to the Keys to Chinese Taxonomy?the third edition?.Then,a soil taxonomy and soil reference were established.The results indicated as follows:1. The soil color in the study area is mainly brown.Most of the soil particle was mainly silt and the soil texture was mostly silty loam.Except for the shrub soil profile,the organic carbon content at the soil surface was above 20g/kg.Organic carbon and total nitrogen content gradually decreased with the increasing of the soil layer depth,whereas the differences among the degree of vertical changes in different soil profiles were found.The soil p H was neutral to alkaline,and the Ca CO₃ content in the soil was high.With the increase of the soil depth,the CEC was gradually decreased.2. There was iron oxide leaching in the soil in the study area.The indicators of fed and fed/fet?fep and fep/fed showed the rule of illuvial horizon>leached horizon>parent material,feo and feo/fed decreased with the depth of soil.The composition of soil minerals in the study area was basically identical,but the content of each component was different.Si O₂?Al₂O₃?Fe₂O₃ and Ca O were the dominated mineral element in Pobulus davidiana pure forest,Pinus tabulaefomis pure forest and shrub;the remaining soil profiles were dominanted by Si O₂,Al₂O₃,and Fe₂O₃.The rank of compositions in decreasing order was Si O₂,Al₂O₃,Fe₂O₃,K₂O,Mg O,Ca O,Na₂O,Ti O₂,P₂O₅,and Mn O.The soil development in the study area was weak,the aluminosilicate rate,ferrosilicon rate and Si-Al-Fe ratio were between 3.90-5.30,9.58-13.87 and 2.77-3.83,which were higher than the strongly weathered soil in the southern region.Soil minerals mainly include chlorite,illite and kaolinite.3. In the soil profile under the main vegetation types on the southern slope of Qilian Mountains,2diagnostic surface horizons were retrieved:mattic epipedon and mollic epipedon;4 diagnostic subsurface horizons:cambic horizon,argic horizon,calcic horizon and calcipan;6 diagnostic characteristics:lithic contact,paralithic contact,soil moisture regimes?udic and ustic?,soil temperature regimes?frigid and gelic?,isohumic property and calcic.The soils in this paper were classified into 3 soil orders,5 suborders,8 groups and 9 subgroups in Soil Taxonomy.4. The 13 soil profiles in the study area were classified into dark felty soil,gray cinnamon soil and chestnut soil in soil genetic classification.Took soil group as a reference object,dark felty soil was sorted into Hap-Udic Cambisols and Hap-Udic Isohumisols;gray cinnamon soil was sorted into Mol-Udic Cambisols,Cal-Ustic Cambisols,Hap-Ustic Cambisols,Hap-Boric Luvisols,Mol-Boric Luvisols and Hap-Ustic Isohumisols;chestnut soil was sorted into Cal-Ustic Cambisols.