6 COMPOSITE TYPE OX THE APACHE NATIONAL FOREST. 



In consequence, but few subtypes are found within the type proper. 

 Practically the only variation is brought about by differences in pro- 

 portion of the three species. This can not always be explained, 

 though in some cases it is undoubtedly due to elevation. Curiously 

 enough, the blue spruce extends at least 200 feet lower than the 

 Douglas fir. This gives a basis for the distinction of one subtype in 

 which only spruce and pine occur. This is always found at the lower 

 altitudinal limits of the type. Two more subtypes may be distin- 

 guished. One is where Douglas fir and yellow pine are predominant, 

 with but an occasional spruce in mixture. This subtype covers a 

 small area, but may be found at any elevation throughout the type. 

 The sparsity of blue spruce on these areas can not be explained. 

 Within the other subtype Douglas fir and blue spruce predominate. 

 This is found only at the upper limits of the type. 



White fir (Abies concolor (Gord.) Parry) and Mexican white pine 

 (Pinus strobiformis Engelm.) are occasionally found in mixture with 

 the three principal species of the type. White fir, which occurs at 

 the upper limits, is the most common. Engelmann spruce (Picea 

 engelmanni Engelm.) is also found at higher elevations, along stream 

 courses. Aspen is scattered here and there throughout the stand. 

 Both it and Engelmann spruce are at present of no commercial 

 importance in the region. 



Since this combination of tree species is so exacting in the matter of 

 site, it is found only in small bodies, which conform in a general way 

 to the topography of the country. Probably about 150,000 acres in 

 all on the Apache Forest is actually covered by the type. 



Although conditions on other National Forests of New Mexico and 

 Arizona are much the same as those on the Apache, this type is not 

 known to occur elsewhere to any considerable extent except on that 

 part of the Sitgreaves Forest which lies adjacent to the Apache, where 

 it covers parts of 12 sections. 



PROBABLE HISTORY. 



Since blue spruce and western yellow pine differ so greatly in sil- 

 vical requirements, it is improbable that they have grown side by 

 side since early youth. There is every evidence that, while western 

 yellow pine has undoubtedly occupied the ground for several genera- 

 tions, blue spruce has but recently come in. Indeed, the present 

 stand of spruce is probably the first generation, a theory borne out 

 bj T the fact that few decaying logs or old stumps of tins species are 

 to be found. The young spruce grows in dense groups beneath 

 mother trees; but the oldest trees as a rule grow singly, very often 

 on the north sides of western yellow pine, where the most protection 

 was afforded. 



In view of these observations it is believed that the stand has re- 

 cently been and perhaps still is hi a transitional stage. The present 



