在以往对黄土高原和秦巴山地等地区土地研究的基础上，提出土地结构是土地空间组合格局与土地演替及土地时间变化规律的观点;分析了土地质与量群聚的对比关系和
土地由一种属性转变为另一种属性的过程;用信息论中的熵函数给出了土地出现的频率和复杂度;用耗散结构理论“涨落”给出了土地自然演替(不可逆)和人为演替(可逆)两种演
替模式。
   

  Land structure and Land succession are one of the theoreticat problems forward position the study of land science，being rassed with deep study of land. Studying on the structure and succession can make integrated physical geography broadly and deeply. With studying the Land structure and land succession in the wading River and the loess plateau of northern shaanxi,that land structure is the veflection of spatial combination pattern of land types and that of communal ratio relations of Land Quality and land quantity are posed According to the entropy function in the information theory,thefrequency and the complexity of land types are givern.
    Land succession , a process of natural features transfering from one Kind of Land type to another，is the reflection of dynamic relationship between land resources and their ecological environment in different time and different natural areas. It is determined by the varance of land structure. Only when the actions of disturbing factors reach the critical point could the land dynamic systems evolute. In theloess Plateau of northern shaanxi,there exist four typical dynamic succession models of land type,i. e.the succession models of Sandy,Loess Mao,Loess Liang and Loess Yuan Land types.