by its own properties and not by extrinsic data, but the illogical 

 procedure of using the habitat, or the stage of ecologic succession, 

 as part of the characterization of a community is a custom of long 

 standing. '^^ The environment is a controlling influence, not a 

 property, of vegetation and the successional status is often hypo- 

 thetical, though important. The most commonly used intrinsic 

 qualities are both analytic and synthetic (see Chapters 3 and 4), 

 and include kinds of species, life-form, population density, cover, 

 frequency, stratification, periodicity, dominance, vitality, and 

 physiognomy. However, many descriptions of vegetation are in- 

 adequate because only two or three of these are considered, while 

 a good description, to be complete, must include most of the 

 qualitative and quantitative properties, with analytic tables as 

 well as good verbal description. Each feature of the community 

 is important, especially in relation to the environment, and a 

 single approach, such as emphasis on dominance, as among some 

 American ecologists, or on characteristic and differential species, 

 as among some phytosociologists, is not adequate. According to 

 Poore, "The more accurate and detailed the information the 

 more valuable the description, which includes as a matter of 

 course the examination of the soil profile and accurate notes on 

 certain features of the habitat. Description by physiognomy and 

 dominance alone, on the other hand, may cause one to ignore 

 the detail for wider aspects, and even to consider that a descrip- 

 tion of the dominant and striking species is the same thing as a 

 description of the synecology of the community." 166.P.45 



Usually the most important criterion in classification is simi- 

 larity, so stands possessing a number of characteristics in com- 

 mon, particularly in species composition and structure, and 

 occupying similar habitats, are placed in one community-type. 

 The recurrence of similar stands in similar habitats has been 

 demonstrated by many investigators. ^^^■^^■^^^•''^'^•^^•^^■^ The rela- 

 tion of stand to habitat is so close (Figure 1-27) that even in the 

 Arctic it has been found possible to predict the vegetation type 

 with a fair degree of reliability when the soil profile and general 

 geographic location are known. ^^^ Although it is true that the 

 complexity of floristic and environmental conditions is so great 



Bases and Units • 173 



