The Influence On Cracks And Reaction Mechanism Of Plants On The Conservation Of Earthen Sites

With high historical value, artistic value, scientific value and social value, earthen sites（ES） is an important part of cultural heritage, and an evidence of the Chinese civilization.Along with development of economic construction, ES protection has been faced with ahuge challenge. The negative effect of the deterioration of the ecological environment of citydevelopment brings a serious threat to fragile ES. Practice has proved that vegetation isclosely linked with the conservation of ES. The mechanical action of root system will bringabout earth cracks, collapse, and natural joint destruction. These diseases have been the toughproblem of ES protection.The main contents of the project are: summarizing the main disease types of ES insemi-humid area based on field investigation; the contribution rate of different species;correlation analysis between each measurement factor of vegetation and crack size;suggestions about the suitable plants and appropriate conservation schemes. The purpose is tomake contributions to the research of damage effects of plants on ES. The results are asfollows:1. After plenty of investigations and statistical methods, the results showed that cracksand collapses, back off of wall bases, gully and holes became the main types of erosion.These damages are a result of plant roots digging, rainfall erosion and weathering. To theearthen sites in semiarid area, cracks caused by the plant roots became the most destructiveand particular damage.2. On the front hall of e’pang palace, the structure and composition of plant communityare simple, and the species diversity is low. Herb layer richness is higher than bush layer andtree layer. The vegetation is dominated by Broussonetia papyrifera, Ailanthus altissima,Ziziphus jujube and Ulmus pumila.3. The contribution of different plants on the crack area: Ziziphus jujuba＞Ailanthusaltissima＞Ulmus pumila, size diameter of the root is the major factor affecting the fracturearea. Plants with deep and well developed root system will bring larger cracks.4. There are4principles for plant screening:(1) Avoid plants with deep and welldeveloped root system;(2) Select local herb with high coverage and easy management;(3) Planting trees around ES to reduce wind and water erosion;(4) he planting species should beconsistent with the site atmosphere.