GIRDLING AS A MEANS OF REMOVING UNDESIRABLE 
TREE SPECIES IN THE WESTERN WHITE PINE TYPE 1 
By Donald R. Brewster and Julius A. Larsen, Forest Examiners, Northern 
Rocky Mountain Forest Experiment Station, Forest Service, United States De- . 
partment of Agriculture 
INTRODUCTION 
Western hemlock (Tsuga Tieteroyhylla) and white or grand fir (Abies 
f wandis), two shade-tolerating species which are found in more or 
ess abundance in the western white pine type in northern Idaho 
and northwestern Montana, must usually be classified as undesirable 
species silviculturally, and for several reasons. In both species the 
liability to infection by heart-rot at an early age causes such a high 
percentage of defect that by the time the trees reach merchantable 
or saw-log size they are apt to be largely or entirely worthless. Even 
when sound, the material produced by these species is of poor quality 
and low value; and in stands in which they occur to any extent the 
stumpage yield per acre is materially decreased by the fact that they 
occupy space which might support more valuable species. 
A particularly undesirable feature is the dense shade cast by these 
trees. The advance growth of hemlock and white fir seedlings and 
saplings which comes in under the mature trees has a tendency to 
monopolize the openings between the larger trees and to repel less 
shade-tolerant species. As a result, on cutting areas where seedlings, 
saplings, and larger trees of these species are present, it is difficult to 
obtain establishment and growth of reproduction of the more 
intolerant desirable species of western white pine (.Pinus monticola) 
and western larch (Larix occidentalis ). 
In order to get maximum production of the most valuable species 
in future stands, the hemlock and white fir trees left standing on 
cut-over areas should be disposed of, and measures to prevent or 
hinder the reseeding of the ground by these species should be taken. 
Possible methods of disposing of undesirable tree species include 
girdling, burning, and poisoning. 
Killing trees by fire is particularly effective with thin-barked 
species, such as hemlock and white fir. Fire may be applied by 
burning piles of forest debris at the base of undesirable trees, or in 
thickets; or it may be applied as broadcast burning of slashings, 
which destroys most or all of the undesirable reproduction and larger 
trees. Broadcast burning, however, in most cases destroys also the 
valuable seed trees and trees left for increased growth, as well as 
most or all of the seed stored in the surface duff. 
Poisoning, or introducing some toxic material into the tree through 
the sap, has been used to some extent for killing hardwood stump 
sprouts in farm clearings in the Eastern States. Although the 
poisoning method may very often be too expensive to be practicable, 
it offers possibilities worthy of investigation. 
1 Received for publication Oct. 28, 1924; issued September, 1925. 
Journal of Agricultural Research, 
Washington, D. C. 
( 267 ) 
Vol. XXXI, No. 3 
Aug. 1,1925 
Key No. F-24 
