FOREST TYPES. 341 



harvested during the present rotation. The physical-type map, then, shows 

 what the land is capable of producing, while the cover-type map shows what 

 the land is producing. If the cover type is important in connection with the 

 present rotation, the physical type is important with relation to the next 

 rotation. The physical-type map indicates the species which may be best 

 grown upon a particular area. This, however, is a matter of comparatively 

 secondary importance in forest administration. Furthermore, questions as 

 to proper species for planting and suitable methods of cutting are solved by 

 special studies rather than in the course of the work of the general reconnais- 

 sance crew. Physical-type maps are doubtless of great silvical and ecological 

 interest, but cover-type maps are more valuable at present to the men who are 

 managing forests in a practical way." 



Tillotson (1913:95) has emphasized the importance of permanent forest 

 types: 



"Ordinarily it is undoubtedly true that better success will attend silyi- 

 cultural operations if due regard be given to the establishment and main- 

 tenance of permanent forest types. It therefore becomes important to learn 

 to distinguish and to classify them. It seems that this will necessitate the 

 division of the country into rather large^ areas, over which the same general 

 conditions of temperature prevail at similar altitudes, these units to be sub- 

 divided into smaller areas, where similar conditions of precipitation both as to 

 amount and distribution exist, and these still further into smaller units, where 

 differences in exposure, topography, or soil exist. On similar areas of this last 

 division the ultimate forest growth may be expected to be the same, both in 

 composition and in character, and it makes little difference in speaking of the 

 permanent types whether they are called, for instance, the north-slope and the 

 south-slope type, or the north-slope Douglas-fir type and the south-slope 

 Douglas-fir type, providing the character of the growth in the region under 

 discussion is known. The physical factors of the habitat will determine the 

 type, and if these are known the character of the ultimate growth will be 

 known by one familiar with the region. To one not familiar with the region 

 any designation of types will in any case necessitate a description of them." 



Zon (1913: 103) points out: 



"One of the most urgent and fundamental silvical tasks of the present 

 moment is the working out of a natural classification of our forests. Since 

 there are no characteristics within the stands themselves which could be used 

 as unmistakable guides for dividing the forest into homogeneous silvicultural 

 units and for acquiring exact knowledge of their silvical requirements, one 

 must necessarily seek such characteristics outside of the stands. Such guides 

 are found in the external environment, with its climatic and soil peculiarities. 

 These alone determine the composition and combination of the species as 

 well as the silvical requirements of the stand. It does not make any differ- 

 ence whether the name of the forest type is derived from the distinctive com- 

 mercial species or topography, provided that in differentiating the forest into 

 types the physical conditions of growth, which are the fundamental and 

 primary causes of the real differences in the stands, are taken as the basis. 

 If forest types are based upon physical conditions of growth, they will neces- 

 sarily also determine the character of growth and make superfluous the further 

 subdivision into quality classes. < _ 



"In a proper forest classification, two things must be distinguished : (a) 

 types of forest as the product of physical conditions of growth, and (6) the 

 condition of the stands as the product of the interference of man or natural 



