Spatial Gene Identification And Conservation Strategies In Tongcheng Historic Urban Area

China has a long history of urban construction,and thousands of years of urban practice has formed rich historical and cultural heritage.A famous historical and cultural city is a space carrier for the spread of Chinese excellent traditional culture and an important proof that China is an ancient civilization.Historical city is a key area with the most complete memory preservation in a famous city,which embodies the value and characteristics of historical city.Spatial gene is the layout relation and combination state of spatial elements,which is the "invariable" internal logic and order rule hidden in the historical evolution.In this thesis,the concept of spatial genes is introduced into the conservation of historic urban areas,and the research path of "extraction of spatial form elements--identification of spatial genes--evaluation of the status quo of heritage--gene protection and inheritance" is taken as the research path,aiming at understanding the spatial characteristics of historic urban areas as a whole,as the basis for guiding the overall protection and inheritance of historic urban areas.First of all,sort out the ancient city pattern,historical and cultural blocks,historical style areas,cultural relic protection units,historical buildings,historical water system related cultural resources.With reference to historical maps,historical data and other relevant documents,combined with field research,three spatial form elements of open space,architecture and street are extracted.The form elements of open space include natural mountains and rivers.The architectural form elements include defense building,political power building,Li-institution building,residential building,commercial and handicraft building;Street shape elements include street network shape and spatial scale.Secondly,on the basis of the extraction of spatial form elements,the logic is taken as constitutive element-combination model-expression character-evolution characteristics.Four types of spatial genes,namely " ecology","axis","frame" and "core",were identified with geographical,stability and interaction.Their element combination patterns were respectively "mountain surrounded by water,human-landscape interaction","function accumulation,form guidance","system association,transportation leading",and "locus of power,cultural center".The expression traits of ecology genes are landscape setting,potential shaping,and interaction between human and landscape.The expression traits of axis genes are traditional ritual axis of function accumulation and urban development axis guided by form.The expression traits of frame genes are traditional ancient city skeleton associated with system and modern road skeleton dominated by traffic.The expression traits of core genes are the core of power symbolized by power and ruling thoughts and the cultural core supported by transportation and public activities.Finally,the status quo of four types of spatial gene heritages in historic urban areas was evaluated from three aspects of structural integrity,element integrity and spatial coordination.The scores of gene heritages were " ecology ","axis","frame" and "core" in order from high to low,and the reasons were analyzed,and then combined with the spatial characteristics of the four types of genes.It was determined that the preservation and inheritance of spatial genes in historic urban areas should follow the principles of holistic protection,sustainable inheritance and the participation of multiple subjects,and various strategies for spatial gene preservation and inheritance were proposed: optimizing ecological pattern to protect " ecology " genes,strengthening visual control and capacity to protect "axis" genes,integrating road network nodes to clarify "frame" genes,and inserting multiple functions to activate "core" genes.