SAMPLE PLOTS IN SILVICULTURAL RESEARCH 47 



its future value in the stand. This position may be classified accord- 

 ing to the following definitions (26, p. 74) adopted by the Society 

 of American Foresters : 



Dominant. Trees with crowns extending above the general level of the 

 forest canopy and receiving full light from above and partly from the side; 

 larger than the average trees in the stand, and with crowns well-developed 

 but possibly somewhat crowded on the sides. 



Co-dominant. Trees with crowns forming the general level of the forest 

 canopy and receiving full light from above but comparatively little from the 

 sides ; usually with medium-sized crowns more or less crowded on the sides. 



Intermediate. Trees with crowns below, but still extending into, the general 

 level of the forest canopy, receiving a little direct light from above but 

 none from the sides ; usually with small crowns considerably crowded on the 

 sides. 



Overtopped. Trees with crowns entirely below the general forest canopy and 

 receiving no direct light either from above or from the sides. These may be 

 further divided into oppressed usually with small, poorly developed crowns, 

 still alive, and possibly able to recover ; and suppressed, or dying and. dead. 



In practice almost no attempt is made to distinguish between the 

 oppressed and the suppressed class, the term " suppressed " being 

 used to cover both classes. As both of these terms have a physio- 

 logical significance, their general use to denote crown position is 

 erroneous. The term " suppressed " is in much more general use 

 than " oppressed." 



This standard classification, widely used in North America, can 

 be applied without modification only to pure and fairly well stocked 

 even-aged stands. Several other tree classifications have been pro- 

 posed, one of the best of which is that used for conifers by the 

 Swedish Forest Experiment Station, given in the appendix (p. 78) ; 

 but all these apply (with more or less success) only to even-aged 

 stands. Many of the stands, particularly of the coniferous stands, 

 that have developed under conditions typical of the United States are 

 uneven aged, understocked, and ragged. In many cases raggedness 

 has been complicated by mixture of species varying in tolerance. A 

 system is needed for classifying trees in uneven-aged stands accord- 

 ing to growth capacity or thrift, as the standard classification 

 indirectly describes trees in the even-aged stand. 



The one such tree classification thus far proposed in North America 

 is that developed by Dunning (20) for the ponder osa pine forests 

 of California. This classification, which is given in the appendix 

 (p. 76), has been applied successfully to similar ponderosa pine 

 forests in other regions, and recent indications are that with modifi- 

 cations it can be applied also to stands of other species. 



INJURIES AND ABNORMALITIES 



All perceptible injury, either past or present, suffered by a tagged 

 or numbered tree should be recorded. The record should show ex- 

 plicitly the location and extent of the injury and its apparent cause. 



Abnormalities of form usually should be recorded as carefully as 

 injury. Abnormalities include burl, crook, heavy fork or unusual 

 branching, misshapen top, heavy butt or root swell, elliptical or 

 irregular cross section of bole, etc. In some studies these have little 

 bearing on the result sought; but since the sample plot is rightly 

 considered a source of data on all growth characteristics of both 

 species and individuals, on reaction to all the factors of site, and on 

 form, such information is logically a part of the record. 



