Soil Morphology,Physicochemical Properties,and Taxonamy Of Mufushan Mt.in Northeast Hunan Province

Mountains is widely distributed in the world.To understand the spatial distribution of mountainous soil resources and ensure the ecosystem service functions and species diversity,the technology of soil taxonomy was employed.In this study,soils along an elevation gradient in Mufushan Mt.of northeastern Hunan Province were collected,and the soil physical and chemical properties were analyzed.Basing on the understanding of soil-forming factors,the macro-morphological characteristics of soil profile,and the physical and chemical properties of soils,this study aims at identifying the soil diagnostic horizons and diagnostic characteristics and classifying soils according to the Chinese Soil Taxonomy（CST）.The main results were listed as follows.（1）Field surveys and historical data analysis showed that Mufushan Mt.was a middle mountain with typical eroded landform.Slopes in the northwest was steeper than those in the southeast.Most of the slopes was steep（>45°）,and were distributed in the middle and high altitude zone.The slope on the top and toe in Mufushan Mt.is gentle（15°to 30°）.The parent rock was an kind of intrusive monzonitic granite,formed during the Yanshanian geological time（about 65 to 150 million years ago）.The soils have a shallow depth of soil depth because of the relatively short soil-forming time.The covered subtropical monsoon climate has an abundant hydrothermal conditions supported high diversity of plant and animal species.The vegetation coverage changes from evergreen broad-leaved forest to evergreen and deciduous broad-leaved mixed forest,deciduous broad-leaved forest,coniferous broad-leaved mixed forest,coniferous forest,and shrub meadow with the increasing altitude.Historically,human activities were dramatic,mainly served as important local production base for vegetables,tea,and wood products.（2）The depth of soil profiles in Mufushan Mt.was relatively shallow.The average thickness of effective soil horizon was 72 cm,and the color（matrix hue）of moist soil ranged from 5YR to 10YR.The soils were loose,porous,and poorly adhesive.The average gravel content was about 26%,and the sand content ranged from 282 to 815 g kg^-1.With the altitude increasing,the effective soil thickness was decreased,the soil color was darkened,the adhesion of soil was increased,and the soil bulk density was decreased.（3）Averaging,the content of soil organic C,total N,total P,and total K were12.48 g kg^-1,0.77 g kg^-1,1.25 g kg^-1,and 30.75 g kg^-1,respectively.Due to the limitation of P,the topsoil C?N（18.2）was slightly higher than the global average value of C:N.But the soil C?P（26.6）and N?P（1.5）were lower than those of the global average values.With the increasing altitude,the content of soil organic C,total N,total P showed an increasing trend,while the C?P and N?P in topsoil showed a decreasing trend.Of the total 25 surveyed soil profiles,84%of the soil profiles were acidic.The base saturation ranged from 8%to 61%,and the cation exchange capacity ranged from 4.57 to 46.56 cmol（+）kg^-1.The soil profiles in low altitude zone had ferric property.The mineral element composition of the soil was dominated by Si O₂（51%）and Al₂O₃（18%）,followed by Fe₂O₃ and K₂O.（4）Totally 6 diagnostic epipedons were found in Mufushan Mt.including anthrostagnic,umbric,and ochric,epipedons,hydragric cambic,and argichorizons.The anthrostagnic epipedon and hydragric horizon were distributed in the low altitude zone<600 m,while the umbric and ochric epipedons were randomly distributed on the vertical zone.The argic horizon was distributed in the low and middle altitude zone,and the cambic horizon was distributed in the altitude belt<1400 m.In addition,ten types of diagnostic characteristcs were found including redoxic features,lithic contact,paralithic contact,anthrostagnic moisture regime,udic soil moisture regime,perudic soil moisture regime,mesic soil temperature regime,thermic soil temperature regime,ferric property and alic evidence.Of the total 25 surveyed soil profiles,about40%soil profiles had paralithic or lithic contact,which were widely distributed along the vertical zone.At the altitude of about 1000 m,the soil moisture regime turned from udic soil moisture regime to perudic soil moisture regime.At the altitude of about 900 m,the soil temperature regime changed from thermic soil temperature regime to mesic soil temperature regime.（5）According to the CST standards,soils in Mufushan Mt.were divided into 4soil orders,6 suborders,10 groups,15 subgroup,21 soil families,and 25 soil series.The soil order distributed along the vertical zone as follows:Cambosols,Argosols,Anthrosols（<600 m）-Cambosols,Argosols（600 to 900 m）-Cambosols,Primosols（900 to 1200 m）-Cambosols,Argosols,Primosols（1200 to 1400 m）-Argosols,Primosols（>1400 m）.According to the GSGC standard,soils in Mufushan Mt.were divided into 4 soil orders,5 soil groups,8 subgroups,8 soil genus,and 16 soil species.The soil order distributed along the vertical zone as follows:Iron bauxite,artificial soils（<1200 m）-luvisols（1200 to 1500 m）-Semi-hydromorphic soils（>1500 m）.Comparing to the GSGC,the CST showed a stronger division ability in classifying soils in Mufushan Mt.