The term ecotype is a useful one, but must be used with three 

 quahfications in mind. The first of these is that "ecotype" must 

 be used with some sort of quaUfier indicating what ecological 

 condition is involved. One must speak of seasonal, climatic, soil, 

 or other ecotypes. Second, an ecotype is something that can be 

 identified initially only by experimental methods. One cannot 

 look at a plant in a specific habitat and term it an ecotype in the 

 absence of any information concerning the plant. Third, the term 

 ecotype is used only at the infraspecific level. One cannot speak 

 of lone Manzanita (Arctostaphylos myrtifolia) as an ecotype 

 adapted to lone clay, since the term ecotype is used only when 

 two or more ecological races occur within a. species. Also, it 

 would be incorrect to call Gilia capitata an ecotype. Gilia capitata 

 contains at least two soil ecotypes, one of which is a serpentine 

 ecotype and the other of which is a non-serpentine ecotype. There 

 may be climatic ecotypes in G. capitata, too, although these have 

 not yet been demonstrated. 



The preceding discussion has been concerned largely with soil 

 effects on vegetation and plant communities, although more 

 emphasis has been placed on individual species than on the com- 

 munities of which they are members. The third and fourth factors 

 that influence the presence and nature of plant communities and 

 vegetation are climate and physiography. Since climate is one of 

 the prime determinants of plant distribution and since physio- 

 graphy is an important determinant of regional climate, the two 

 factors will be discussed together rather than as independent 

 entities. 



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