The Influence Of Plants On The Rammed Earth Of Earthen Sites In Xi’an

The earthen sites are ancient ruins with historical,cultural and scientific values.They are direct evidences of the origin of Chinese civilization and important parts of cultural heritage.Due to the poor water-resistance of the soil,wind erosion and rain erosion have become the most important influencing factors of earthen sites,and earthen sites have been eroded away or even disappeared because of wind and rain.The theory and practice of earthen sites protection prove that vegetation is closely related to the protection of.Plants are generally found on earthen sites,and the earthen sites with plants are relatively well preserved.Plants have played a positive role in protecting earthen sites from wind and rain.Plants themselves have a dual role in earthen sites.The negative effects of plant roots,which cause cracks in the bauxite soil and accelerate changes in soil structure and properties,are the most difficult problems in conservation work.Using literature research,field investigation and experimental analysis methods,this paper summarizes the main types of diseases and common plants and their succession characteristics of earthen sites in Xi’an based on a field survey of the E’pang Palace Site,the Han Chang’an City Site and the Duling Site.Then,taking the E’pang Palace Site as an example,the most serious disease platform margin was selected as the research area.The soil samples from the roots of the dominant plants on the platform margin were used to study the effects of different plants on the bauxite structure,analyze the differences in the effects of different plants on bauxite and the correlation between measured soil properties,and summarize the characteristics of the influence of plants on the soil properties.These contribute to the study of the negative effects of vegetation on earthen sites.The results are as follows:(1)The main types of diseases in the earthen sites in Xi’an include cracking and collapse,foundation erosion,surface erosion,gully development and cave remains.The influencing factors can be divided into physical and chemical effects.The physical factors mainly include plant roots,animals,wind erosion and rain erosion.The chemical factors are mainly the hidden damage of plant roots to rammed earth,that is,the influence of plant roots on soil properties.(2)The plant diversity of the platform margin of the E’pang Palace Site is lower,and plant species richness in herb layer is higher than that in arbor layer and shrub layer.Theplant diversity of the nursery in the center of the platform is higher,and the plant species richness of the arbor layer is higher than that of the shrub layer and the herb layer.The main dominant species of the platform margin include Broussonetia papyrifera,Melia azedarach,Ailanthus altissima,Paulownia fortunei and Zizyphus Jujuba.The plant diversity of the Han Chang’an City Site is higher,and the plant species richness of herb layer is higher than that of arbor layer and shrub layer.The main dominant species include,Zizyphus Jujuba and Cyperus rotundus.The plant diversity of the Duling Site is lower,and the plant species richness of the arbor layer is higher than that of shrub layer and herb layer.The main dominant species include Broussonetia papyrifera,Rubia cordifolia and Ixeris polycephala.(3)The vegetation succession characteristics of the soil sites in Xi’an area are herbaceous communities composed of Chloris virgata,Cyperus rotundus,and Artemisia capillaris,Shrub communities mainly composed of Zizyphus Jujuba,complex communities with tree-shrub composed of Zizyphus Jujuba and Broussonetia papyrifera,arbor communities consisting mainly of Broussonetia papyrifera.(4)The most common difference in soil properties between dominant plants(including rhizosphere soil and non-rhizosphere soil)and bauxite is humic acid,and the least difference is fulvic acid.With the increase of soil depth,the most remarkable factor on the soil properties of the five woody plants is Paulownia fortune,and the least is Broussonetia papyrifera.The effects of soil biological characteristics on bauxite are,in descending order,paulownia,jujube,skunk,bitter buckwheat and mulberry.The effects of soil biological characteristics of Paulownia fortunei,Zizyphus Jujuba,Ailanthus altissima,Melia azedarach and Broussonetia papyrifera on bauxite decrease in turn.