Juno 14, 1924 
Growth on YeUow Pine Lands in Idaho 
1145 
this infection assumed rather serious proportions, causing a loss of 3.09 per cent 
of the volume. While the loss due to mistletoe is not alarmingly high on any of 
the plots, the indications are that the death rate will increase from year to year. 
The information at hand indicates that the cutting of infected trees is the most 
practical method of control ( 6 ). Every effort should therefore be made to 
remove moderately and heavily infected trees when cuttings are made. 
Death from suppression obviously results in a relatively small volume loss, 
although the number of dead trees may be large. The habitual occurrence of 
western yellow pine in fairly open stands which would seem to predicate a small 
amount of suppression is, to some extent, counterbalanced by the tendency to 
form scattered groups, with resultant heavy losses in the smaller diameter classes. 
The later records on these plots will supply valuable information as to the relative 
light requirements of the two species, their resistance to overtopping and, on the 
cut-over plots, their ability to recover upon being released. 
It is noteworthy that on the cut-over plots all of the general lack of vigor and 
thrift is either the result of suppression which took place before the cutting and 
from which the western yellow pine had not recovered, or is due to the loss of a 
considerable part of the crown through careless felling of adjacent trees during 
logging. It would appear that for trees showing a lack of vigor on plots Nos. 1 to 
3 inclusive, 3.31 is too high a percentage for recent cuttings, even though the trees 
comprise only 0.58 per cent of the total cubic volume on the cut-over area. 
(See Table III.) The need for greater care in logging to reduce the injury to re¬ 
served trees and to utilize all suppressed trees which are merchantable can 
scarcely be overemphasized. The plots show a significantly high percentage of 
trees in the mature and overmature virgin stands lacking in vigor and consisting 
of injured, defective, and decadent trees. 
Porcupines have caused some injury in certain localities. The actual volume 
loss due to this agent is small. Saplings are frequently killed by girdling, but large 
trees are rarely killed. However, the leaders are often girdled, which sets the 
tree back from 5 to 15 feet or even more in height. New leaders are usually 
developed, but constrictions and pronounced crooks remain as evidence of the 
attack, which may even appreciably affect the amount and grade of lumber 
sawed from trees which recover. 
NATURAL REPRODUCTION 
One of the main objects of silvicultural management is to secure prompt restock¬ 
ing after cutting. In fact, a forest in which restocking does not follow cutting is 
doomed ultimately to annihilation. In the forests of the Intermountain region, 
where artificial regeneration is subject to numerous adversities and an almost 
prohibitive cost (7), natural reproduction is of the utmost importance. Natural 
reproduction in the western yellow pine type, therefore, has been one of the 
foremost subjects of investigation in central Idaho. The more important results 
of these studies have already been published and therefore in the following 
paragraphs only the principal results will be summarized. 
The effect of sheep grazing upon coniferous reproduction and the extent to 
which this damage can be reduced by more careful use of the range was made the 
subject of an intensive study by Sparhawk ( 10 ).. Detailed information on germi¬ 
nation, survival and causes of death of seedlings with particular reference to 
grazing injury was secured on 151 small sample plots in the Payette National 
Forest. This study emphasized the general principle that the extensive browsing 
of coniferous reproduction and the less palatable forage species is the best evi¬ 
dence that the range is being overgrazed. In many instances on cut-over areas 
in the course of regeneration it may be desirable to reduce materially or even 
to eliminate grazing, particularly that of sheep. 
96462—24t-7 
