The Distribution And Influencing Factors Of Phytolith In Different Types Of Dune Topsoil In Horqin

Horqin Sandy Land is located in a typical ecological transition zone in China,and the topsoil is strongly eroded by wind.The discussion on the horizontal migration law of phytolith in the topsoil of type sand dunes is beneficial to the study of the modern process of phytolith,and has important scientific significance for quantitatively reconstructing the paleoenvironment of sandy land and improving the accuracy of predicting climate change in the future.In this paper,the topsoil of windward slope and leeward slope of different types of sand dunes in Horqin sandy land were sampled,the organic matter content and particle size characteristics of topsoil were determined,and the phytolith in topsoil was extracted and analyzed.Based on the sampling of typical plant communities,phytolith was extracted and analyzed,and the combination characteristics of topsoil phytolith in different types of sand dunes,windward slope and leeward slope in Horqin sandy land were obtained.the quantitative correction relationship of topsoil phytolith to surface plant community was established,and the reasons for the differences of topsoil phytolith in different types of sand dunes were discussed.The main conclusions are as follows:1.A total of 37 types of phytolith were identified in the four types of typical dune topsoil in Horqin sandy land.Short-cell phytolith,Elongate,Lanceolate and Blocky were absolutely dominant in the topsoil assemblage of Horqin sandy land,and the average cumulative percentage content was 90.78%.The phytolith concentration of most samples of dune topsoil in Horqin sandy land is in the range of 20?600×10~2grains/g,with an average of 237.09×10~2grains/g.The percentage content of topsoil phytolith assemblage can also be used to effectively distinguish fixed sand dunes,semi-fixed sand dunes,semi-mobile sand dunes and mobile sand dunes.The correct rates of discriminant analysis of windward and leeward slopes of fixed dunes,semi-fixed dunes and semi-mobile dunes are all above 98%.The established discriminant function can effectively distinguish them.2.A total of 30 types of phytolith were identified in the surface plant community samples of different types of sand dunes in Horqin sandy land.The short-cell phytolith in the phytolith assemblage is the most abundant type of phytolith in the surface community,mainly Bilobate,less Trapeziform crenate,Saddle and Rondel.The content of Lanceolate is the same as that of Trapeziform crenate,the content of Elongate is lower,and the content of Bulliform,Blocky and Tabular is very low.The total concentration of phytolith in the surface flora of different types of sand dunes varies greatly,the concentration of phytolith in the community of fixed dunes is the highest,and the average value of semi-fixed dunes is lower than that of fixed dunes and slightly higher than that of semi-mobile dunes.There are obvious differences in the characteristics of phytolith assemblage on the surface of different types of sand dunes,and the use of community phytolith assemblage characteristics can effectively distinguish different types of sand dunes.3.In this paper,the representative evaluation and deviation correction of topsoil phytolith in different types of sand dunes in Horqin sandy land were realized,and the correction coefficient(R value)of topsoil phytolith to surface plant community was established.the correct rates of cross-verification discrimination for the three types of sand dunes before and after correction are 51.8%and 99.3%respectively,and the deviation of the representative degree is effectively corrected by the corrected topsoil phytolith.In this paper,the discriminant function of topsoil phytolith for different types of sand dunes and the proposed correction coefficient of topsoil phytolith are used to quantitatively reconstruct the climate characteristics since Holocene in Daike section of Songnen sandy land.before and after correction,each index is consistent with the climate change law indicated by the original index.4.In sandy area,surface vegetation is an important source of soil organic matter,and the concentration of phytolith in soil mainly depends on the content of organic matter.Correlation analysis shows that there is a significant correlation between topsoil phytolith concentration and surface coverage(r=0.290,P<0.01).The sand dune topsoil phytolith may migrate horizontally to a certain extent because of the strong wind force,so it is reasonable to use non-local or regional vegetation to explain the sand surface phytolith assemblage.However,the amount of wind migration in Horqin sandy land does not affect the clear distinction of the characteristics of the combination of fixed sand dunes,semi-fixed sand dunes,semi-mobile sand dunes and windward slopes and leeward slopes.