Pedogenic Characteristics Of Loess And Its Environmental Significance Under Different Land-use Type In The Upper Of Jialing River

Loess is a good carrier to record the paleoenvironment.The study of loam formation characteristics of loess or aeolian sediments is of great scientific significance to reveal the process of soil formation and the evolution of regional paleoenvironment.However,due to the interference of late environmental change or land use change,the properties and structures of some sedimentary strata during the sedimentary period may be affected or even lost,thus affecting the accuracy of paleoenvironmental reconstruction.There are abundant soil studies on quaternary dust deposition,but there are few studies on the relationship between land use change and modern climate env ironment and sedimentary strata.The study of loam formation characteristics of leeward sedimentary strata in modern climate environment and the influence of land use change on loam formation characteristics is helpful to deeply understand the relationship between loam formation and modern climate environment and land use change,and further enrich the study of loess and soil genetics.This article takes the Jialing River upstream of the loess parent material on the development of soil profile as the research object,comprehensive utilization of profile morphological characteristics,soil p H,organic matter,calcium carbonate,magnetic susceptibility,granularity and element geochemical characteristics such as soil indicators,combining section use type and multi-angle and soil characteristics of the region of the loess comparative study,the results show that:?1?The loess particles in the upper reaches of Jialing river are mainly composed of silty sand.Glue powder ratio,magnetic susceptibility,the CIA index,A-CN-K chemical weathering parameters such as the triangular figure indicates the soil strength is weak in loess profile in the Jialing River upstream,similar to the quaternary loess in loess plateau,in the early stages of weathering of soil,and weak weathering degree in nearby the Hanjiang river upstream of the loess,Chengdu clay and Shu loess under the middle and lower reaches of the Yangtze river,speculated that the Jialing river upstream of the loess is the extension of the quaternary loess in loess plateau,across the qinling accumulation during monsoon is strong;The genetic characteristics such as grain size and elements indicate that the loess in this region is not strongly affected by the soil formation transformation in the modern natural environment.?2?The impact of different land use on the hue value,Mn O,Ti O₂,Na₂O/K₂O in the section was minimal,while the indexes of calcium carbonate content,susceptibility,viscose-powder ratio,sand content,Ca O,P ₂O₅,Sr,Zn,Rb/Sr,ba were significantly different in different land use sections,and the surface variation was the strongest.In the sect ion surface of forest land,wasteland and grassland with little human interference,Rb/Sr,Fe ₂O₃/Mg O,CIA,ba,Saf,residual coefficient?Ki?,alkali regression coefficient and other indicators have a certain degree of response to the surface natural envir onment,while particle size and magnetic susceptibility have weak effects,which basically inherit their parent material characteristics.However,the profile of dry land and orchard was strongly affected by human interference in a short time scale,and the variation of each index of the profile was stronger than that of forest land,wasteland and grassland.?3?A layer of dry land and orchard profile,the organic matter,magnetic susceptibility,sticky powder ratio,Fe/Mg,Rb/Sr,weathered eluvial coefficient?ba?,eluvial coefficient?Ki?index indicates that A B and C layer increased trend in weathering,and the CIA value rate of iron,silicon aluminum?Saf?,alkali coefficient decreases indicates the weathering trend,each index indicating environmental significance of inconsistent phenomenon,Na ₂O/K₂O affected by land use change little;Therefore,it is nec essary to pay attention to the applicability and preconditions of indicators in the selection of environmental substitution indexes.?4?Correlation analysis shows that as the soil strength increases,the contents of Al₂O₃,Fe₂O₃ and K₂O elements in the profile increase,while the leaching effect of Ca O is obvious and the loss is more,which is negatively correlated with the magnetic sus ceptibility.The dry land profile is strongly affected by tillage and fertilization,which is manifested as the sand grain and P₂O₅ in the profile,and the organic matter has a significant positive correlation with Cu,K₂O,Zn,P₂O₅ and other elements.