


THE TREE. | 19 
had been killed, but none of a diameter above 20 inches. The injury 
to the mature yellow pine was very slight. Few of the larger trees 
were burned through the bark. 
WIND. 
The extensive root system of western yellow pine, especially the 
strong laterals, enables the tree, under ordinary conditions, to with- 
stand severe wind pressure. In early spring, immediately after the 
snow has melted, and during the summer rains, however, the com- 
bination of soggy, water-soaked soil and high winds results in con- 
siderable windfall. Observations made on the Coconino National 
Forest show that, unless left in groups or otherwise protected, seed 
trees which remain after a stand has been removed are very likely 
to be wind thrown. Isolated trees that have always grown in the 
open can, of course, withstand the wind; the damage occurs when 
trees that have been growing with other trees in dense groups are 
suddenly exposed to its full force. 
A tract of 480 acres on the Tusayan National Forest was logged 
during August, September, and October, 1909, after about one-third 
of the stand had been carefully marked for cutting. Yet in Sep- 
tember, 1910, a year later, 8 blackjack and 10 yellow pine, total- 
ing 2,250 and 8,520 feet board measure, respectively, had been blown 
down. The total windfall of 10,770 feet was, however, only 0.0067 
per cent of the stand left after cutting. In this case the area: was not 
exposed to the full force of the wind, and the marking was carefully 
executed with a view to preventing windfall. On less favorable situ- 
ations and with less careful marking the loss has been as much as 2 
per cent of the total stand left. 
FROST AND SNOW. 
Young seedlings of western yellow pine are susceptible to frost 
damage, particularly when they have not come up under the pro- 
tective cover of brush. Moreover, dense reproduction, even from 2 
to 5 feet in height, often suffers severely from either very early or 
very late frosts. In the Lincoln National Forest, along the Rio 
Bonito, there was considerable damage to young western yellow pine 
from frost in 1907. South of Sitgreaves Mountain, in the Coconino 
National Forest, dense reproduction was seriously damaged by frost 
in 1905. The results of experiments indicate that seedlings which 
have grown up under brush cover are not liable to frost, but may 
damp off during wet weather. Mature timber, also, is not damaged, 
and frost cracks in green timber are unknown. During the winter, 
however, frost in saw logs makes milling expensive unless the logs 
are thawed in a hot-water mill pond. 

