FOREST TYPES. 337 



light and water relations, and that of stems is an indicator of annual fluctu- 

 ations in rainfall, and hence climatic cycles. Flowering and seed-production 

 also have their indicator values, but these are of secondary importance. 



Serai communities differ chiefly from climax ones in indicating edaphic 

 conditions or habitats rather than climate. Their peculiar value lies in the 

 fact that they may at the same time indicate the nature of the initial area or 

 disturbance, the particular stage of development in the succession and the 

 habitat, and the final association or climax. Such stages are denoted by the 

 associes, and minor stages or variations by the consocies, while the socies 

 denotes subordinate differences within these. These three types of com- 

 munity, and the series of associes which constitute the sere, form a complete 

 scale of variations and changes, upon which the problems of forest mainte- 

 nance, of reforestation and afforestation, must be based. In short, while the 

 climax indicates the permanent forest of a region, the seres indicate the 

 methods and materials which must be used in hastening, maintaining, or 

 postponing the climax community, which is inevitable under natural con- 

 ditions. It is obvious that serai communities furnish indications from compo- 

 sition, density, and growth essentially similar to those of the climax (plate 86). 



FOREST TYPES. 



Bases. — The nature of forest types and the bases for their distinction have 

 been fruitful subjects of discussion among foresters. Graves (1899) seems to 

 have been the first to characterize forest types definitely : 



"If nature is left undisturbed, the same type of forest will tend to be pro- 

 duced on the same classes of situation and soil in a specified region. There 

 will be variations within the type, but the characteristic features of the forest 

 will remain constant, that is, the predominant species, density, habit of trees, 

 reproduction, -character of undergrowth, etc. If a portion of the forest is 

 destroyed by fire, wind or otherwise, the type may for the time being be 

 changed, but if left undisturbed, it will revert to the original form, provided 

 the condition of the soil is not permanently changed." 



Zon (1906) states: 



"The first step in any silvical study or attempt at forest management is to 

 reduce the great variety of stands to a small number of types, each having 

 characteristic features of its own and requiring a distinct treatment. The 

 nearer we come to establishing natural types of forest growth, the deeper 

 we penetrate into the true relationship existing between these types and the 

 factors that produce them, and this is the most important contribution to 

 silvics. " 



The changes brought about in a forest by man or by accidents are not 

 regarded as a basis for the establishment of fundamental forest types, but it 

 is recognized that such changes do produce temporary or transient types. 

 The essential agreement of the basis proposed by Graves and Zon with the 

 principles of succession and the distinction between climax and developmental 

 communities was pointed out by Clements (1909 : 62) : 



"Reproduction is the forester's term for development or redevelopment; 

 it is the complex response of a formation to its habitat, which leads to succes- 

 sion. The result of reproduction is a forest type of succession, an ultimate or 



