Altitudinal Distribution Of Soil Physicochemical Properties And Taxonomy Of Mangshan Mt.in Southern Hunan Province

Understanding the nature of mountain soils and classifying soil resources scientifically and systematically are of great significance to the function of mountain ecosystem services and conservation of mountain species diversity.In this study,the soil of Mang Mountain in south of Huanan was selected as the research object,and the historical literature and field survey were integrated to summarize the soil-forming environmental conditions.The soil profile was described in the filed combined with laboratory soil physical and chemical property tests,and soil occurrence properties were analyzed and classified according to systematic classification criteria.The aim is to improve the basic classification units of mountain soils in Hunan province,and to provide scientific basis for the protection and rational utilization of soil resources in subtropical mountains.The main results are as follows:(1)In terms of soil formation environment,Mang Mountain belongs to the middle mountainos terrain of Nanling Mountains,with strong terrain cutting,steep slopes and deep valleys,and extensive distribution of young soil.The foot of the mountain belongs to the central subtropical humid monsoon climate with abundant water and heat resources.The middle and upper part of the mountain has a warm and cool climate,with obvious climate difference between the north and south slope.In winter,there is often an "inverse thermosphere" phenomenon where the temperature at the top of the mountain is higher than that at the foot of the mountain.The mountain is mainly granite body,which is an intrusin of Yanshan period.The formation time is short,and the embryonic soil is widely developed.With a long history of human activities,the main land use type is woodland.(2)In terms of the macroscopic morphological properties of the soil profile,the soil development in Mangshan mountain is generally shallow,and the soil thickness of soil becomes shallower with the altitude rises.The main soil color tone was 10YR,with a variation range of 5YR to 2.5Y,and the brightness was mostly 6.With the deepening of soil profile,the soil consolidation changes from loose or very loose to slightly compactness and compactness.Soil adhesion was from non-adhesion to adhesion.In the middle mountain elevation zone,the distribution of solidity is low altitude>high altitude>middle altitude,and the distribution of adhesion is high altitude>low altitude>middle altitude.(3)In terms of soil physical and chemical properties,the soil is sandy.Sand content is significantly and positively correlated with altitude,while clay content is significantly and negatively correlated with altitude.The soil was acidic or weakly acidic,the base was highly unsaturated,and exchangeable H+and CEC were significantly and positively correlated with altitude.The total mineral composition of the soil was dominated by SiO2 and Al2O3,which accounted for 54%～76%(average 63%)and 20%～32%(average 29%)of the total soil mineral composition of soil,respectively.The contents of soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen,total potassium and available phosphorus were significantly and positively correlated with altitude,but the content of available potassium was significantly and negatively correlated with altitude.(4)According to the criteria of Chinese Soil System Classification Retrieval(3rd edition),the diagnostic layers included barren surface layer,thin surface layer,embryonic layer,clayed layer and low activity iron-rich layer.Diagnostic characteristics include stony contact surface,quasi stony contact surface,moisture status of normally wet and moist soil,thermal and warm soil temperature status,iron properties,humus properties and aluminum phenomena.Four soil classes,six subclasses,11 soil groups and 13 subgroups,16 soil groups and 21 soil series,are classified as iron-rich soil,leached,embryonic and neoplasm soils.According to the classification standard of the system,the vertical zone spectrum of the soil in Mang Mountain is as follows:iron-rich soil,embryonic soil(400～700 m),eluvial soil,embryonic soil,neoplasm soil(700～1300 m),eluvial soil,embryonic soil(1300～1800 m).(5)According to the principle and standard of soil geogenetic classification,three soil classes,four soil groups,seven soil genera and 13 soil species are classified as ferrite,leachate and hemihydrate soils.The vertical zone spectrum of soil in Mang Mountain is as follows:ferrite(400～1200 m)-leached soil(1200～1400 m)-hemihydromorphic soil(1400～1800 m).(6)In the reference of different soil classification systems,the CST classification system was compared with CGST,WRB and ST classification systems.In CST,the dominant reference type of iron-rich soil was strongly leached soil in WRB,and the dominant reference type in ST was aged soil or leached soils.In CST,the approximate reference type in WRB is dark barren soil or highly activity and strong acid soils,and the dominant reference type in ST is old soil or leachate soils.The definitions and restrictions of embryonic soil in WRB and ST were similar,but the approximate reference type in ST is embryonic soil.In CST,the dominant reference type in WRB is thin layer soil,and the definition and qualification conditions in ST are basically the same.