A Study On The Role Of Lichens And Mosses On The Primitive Soil Formation Process In Alpine Regions

Soil is the material basis for human survival and maintains the stable balance of the earth’s ecosystem.However,the development of soil into a complete profile goes through a long process of weathering,transport and soil formation of bedrock.The process of soil formation,which starts from the exposure of rocks to microorganisms and lower plants to the settlement of higher plants,is called the primitive soil formation process and is the starting point of soil formation,which is of great scientific significance to understand the soil development.As the roof of the world,its unique geographical environment of Qinghai-Tibet Plateau is an ideal place to study the primitive soil formation process,but the current research on the plateau soil development focuses on the soil formation process after the growth of higher plants,and the primitive soil formation process on the rocks from after the growth of lower plants to before the settlement of higher plants is not clear.Therefore,the study of the primitive soil formation process on the Qinghai-Tibet Plateau is of great significance to the systematic understanding of the development process of plateau soil.The original soil(lichen soil and moss soil),bedrock,bare soil,lichen and moss at 13 sampling points in the southeast of Qinghai Lake Basin and 6 samples of atmospheric fallen dust in the basin were selected as the research objects.Firstly,the types of bedrock were identified,and the sampling points were classified according to the types of bedrock.By testing the soil granularity,mineral composition,p H value,TOC and element geochemical content,combined with the present achievements of other soil profiles in the basin,discussed the effects of lichen and moss on the original soil-forming process in Qinghai Lake Basin were discussed.The results show that: 1.The particle size distribution of the original soil and atmospheric fallen dust in the southeastern part of Qinghai Lake basin was mainly in a three-peaked distribution,and the particle size of lichen soil and moss soil were comparable,and the atmospheric dust was basically dominated by sandy silt;the original soil was dominated by neutral soil and alkaline soil,and the alkalinity of moss soil was stronger than that of lichen soil.2.The mineral composition of the original soil and atmospheric fallen dust was dominated by quartz and plagioclase,with more than 70%,followed by illite and chlorite,and less by dolomite,mica and hematite.From the characteristics of mineral composition of lichen soil,moss soil and atmospheric fallout,the material source of the three may have consistency,but the material weathered from bedrock was relatively less.3.From the CIA values,the original soil as a whole is in the stage of weak chemical weathering,and the weathering degree of lichen soil in the second stage of the original soil formation process was lower than that of soil weathering by moss weathering in the third stage.4.Through the analysis of grain size and element geochemistry,the original soil was similar to the atmospheric fallen dust and the aeolian materials in Qinghai Lake area,indicating that the sources of the materials were the same,indicating that the original soil may be mainly aeolian sediments.5.Lichens and mosses captured atmospheric fallen dust,absorb nutrients from fallen dust,and at the same time precipitate foreign substances rich in nutrients for the formation of the original soil,and the contents of TN and TP in lichen soil were higher than those in moss soil.