CLASSIFICATION SYSTEMS 



Ecosystem classifications in the United States have been developed based on a 

 variety of criteria ranging from primarily biological'''" to primarily physical." A 

 relatively standard classification originally developed by Daubenmire,'^ in the 

 western United States, is based primarily on vegetation. The units derived from this 

 classification are called habitat types. This approach that now extends to at least half 

 of the forested lands in the west'^ rests on the assumption that vegetation is the best 

 integrated expression of the total ecosystem. 



In other schemes, an attempt is made to classify ecosystems on the basis of biotic 

 and abiotic criteria so as to identify land units where ecosystem components are 

 integrated in a similar way. The concept of integrating more than one system to 

 identify homogeneous units of land was expressed in ECOCLASS.''' A potential 

 vegetation classification and a land and aquatic system were linked to define 

 ecological units. Combinations could be made from selected levels of the hierarchy in 

 each respective system. Dashed lines in Figure 1 indicate possible integrations which 

 could yield an integrated classification unit useful to management. Modified versions 

 of ECOCLASS" have been developed for some areas in the western United States. 



The concept was expanded to link classification to management needs in 

 ECOSYM.'* Several component classifications, each with its own hierarchy of levels, 

 were developed on the basis of recognized land-management needs. In this 

 procedure, different approaches to classifying the landscape or its resources are 

 viewed as a series of overlays and are only integrated by the manager for a particular 

 purpose. The integrity of each classification remains intact through many combina- 

 tions and recombinations. 



Another concept of integration is found in the land systems approach. Land 

 systems inventory refers to an integrated approach to land survey in which areas of 

 land, as ecosystems, are classified according to their ecological unity. The classifica- 

 tion process involves the delineation, description, and evaluation of relatively 

 homogeneous units of land at the local or regional scale. This approach assumes that 

 all components fnay not be equally significant at different levels in the spatial 

 hierarchy nor that it is possible to deal with all components simultaneously. It 



Vegetation System Land System Aquatic System 



Formation -^ -^^ Province -v. ^ Order 



- "^ ^ " ^ ^ 



^ '' ^ " -^^ 



Region -^r^ -^ Section "*-~~ '^"^ Class 



"^ " ^^ .^ " ^ '~ "-^ '^ 



Series ■* C '^"^ Subsection ■*< 7- "5^ Family 



"^•«*» -^ "^ ^^ ^^ ^ -^ 



^ ^~^ — ^ Landtype ,_^ — " "^ ^ 



^rl "V"*' Association "" ~^-^— _ — "^.^^ Aquatic Type 



Habitat Type '^^Xir - ^ -^''^ ^^J^--"^'-- Association 



^^<. '2.^" Landtype •<r'_7[^ ^ " 



Conmunity Type** '^Landunit ^'^ — """ Aquatic Type 



' Ecological Land Units ' ' Ecological Water Units ' 



Figure 1 . Basic systems of the ECOCLASS method, showing the hierarchical classifi- 

 cation and possible combinations. (Adapted from Corliss'") 



18 



