Introduction 



Classification groups things that are similar and separates 

 things that are dissimilar. Any classification forms a 

 framework for organizing knowledge about things. Most 

 classifications include devisions or levels to form hier- 

 archical organization. The specific structure of a classifi- 

 cation is strongly influenced by its intended use, either 

 expressed or implied. Classification is not an inventory in 

 itself; it is a framework for partitioning heterogeneous 

 populations into more manageable and homogeneous 

 subunits. Within this framework, inventories can be con- 

 ducted to obtain required data and information about 

 specific objects. Also, classification structures data and 

 permits rapid analysis of complex situations. 



Baily and others (1978) discussed different approaches 

 and kinds of land and resource classifications. Federal 

 laws emphasized the need for a uniform classification 

 system. These include The Forest and Rangeland Renew- 

 able Resources Planning Act of 1974 as amended by The 

 National Forest Management Act of 1976, The Federal 

 Land Policy and Management Act of 1976, and The Soil 

 and Water Resources Conservation Act of 1977. These 

 laws require several Federal agencies to assess the condi- 

 tion and status of the Nation's lands and renewable natural 

 resources on a periodic basis. They also require exchange 

 of information about the resources to develop assess- 

 ments of resource conditions and status. In some States 

 and localities, land use planning is required by law; in 

 others, by administrative policy. 



To assess natural resources on a periodic basis, Fed- 

 eral agencies must be able to define the inherent biological 

 potential of the land. This classification was developed to 

 accomplish this. The classification is based on relatively 

 permanent land features instead of land use. 



There are two general kinds of ecological classifica- 

 tions for natural resources — integrated and component 

 or ecosystem element. An integrated classification unites 

 elements of the land — vegetation, soil, landforms, cli- 

 mate, and water — to form a coordinated entity. The sys- 

 tems developed and proposed by Austin (1981), Bailey 

 (1980a), and Wiken and Ironside (1977) are examples of 

 integrated classifications. The underlying principle of 

 integrated classification is to develop a system that ex- 

 presses the interactive character of the land's elements as 

 a unit in relation to surrounding land units in a spacial 

 hierarchy (Rowe 1972). A key feature of this approach is 

 developing the classification based on the known func- 

 tional relationships among the land elements. The units 

 derived express what is theorized to be ecologically im- 

 portant in the landscape. Two basic assumptions are that 

 data and information are available or can be obtained to 



develop the system, and the interrelationships among the 

 land's elements are well understood in defining the inte- 

 grated units. 



An ideal integrated ecological land classification sys- 

 tem might be a single hierarchy whose units are defined in 

 terms of all identifiable environmental factors and the 

 interactions among them. This ideal can only be approxi- 

 mated. To develop such a hierarchy requires a high level 

 of understanding of the interrelations among land ele- 

 ments — and an equally high level of agreement among 

 users on specific criteria selected to define units at each 

 hierarchical level. 



Ecosystem element classification describes parts of 

 the land — the soil, vegetation, landform, water, and 

 climate — to form a hierarchical classification of each sep- 

 arately. The soil classification system used in the United 

 States (USDA, Soil Conservation Service 1975) is an 

 example of an element classification. Kuchler (1964) pre- 

 sented a map of the potential natural vegetation of the 

 United States. Penfound (1967) described a vegetation 

 classification system of the United States. The United 

 Nations Educational, Scientific, and Cultural Organiza- 

 tion (UNESCO) presented an open-ended worldwide veg- 

 etation classification system (UNESCO 1973). 



The principle of the element approach to land classi- 

 fication is to deal initially with each element as an entity, 

 defining and describing the classes on the basis of pri- 

 mary characteristics. Thus, the element approach to land 

 classification allows users to apply only those elements 

 and levels that are needed for an intended use. Not all ele- 

 ments have to be applied for every management applica- 

 tion. Nor is the most detailed level of classification re- 

 quired if some more general level is sufficient. 



The element approach to land classification is an 

 approximation of integrated land classification because 

 of the way each element classification is developed. Each 

 element hierarchy represents in fact an integration of 

 physical and biological factors. For example, effects of 

 moisture and temperature are considered in the classifica- 

 tions of plant communities and soils, such as boreal for- 

 ests (forests developed in cool climates) and Aridisol soils 

 (soils formed in aridic climates). Further integration is 

 accomplished by selecting classification criteria from sev- 

 eral element hierarchies and combining them to extend 

 the scope of the integration. 



This stage of integration, as compared to the ones 

 previously discussed (Austin 1981, Bailey 1980a, Wiken 

 and Ironside 1977), is descriptive. Characteristics from 

 more than one element are combined to define a new 

 unit. This unit is specifically defined and is assumed to 



