2 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE. 
ditions were 'frequently severe, limiting growth and reproduction. 
Sentiment toward the practice of silviculture was generally apathetic 
or actively antagonistic. 
With these conditions prevailing, the forester faced the problem 
of improving the health of the stand, increasing the rate of growth, 
and securing more pine reproduction to the limited extent that one 
cutting permits, In 10 years' time a large amount of valuable data 
has been accumulated which has served to indicate good silvicultural 
practice. There is an increasing demand for reliable growth sta- 
tistics in the preparation of working plans, not only for public 
forests but for private timber also, as evidenced by recent requests 
from several private timber owners contemplating management of 
their tracts on a permanent yield basis. In addition, all possible in- 
formation should be available for those directly or indirectly con- 
cerned with the forests and their products in considering the reme- 
dies for forest devastation and the establishment of forest policy 
for the State and region. 
As indicated in the text, some of the conclusions drawn from this 
study as to the best silvicultural practice are not immediately ap- 
plicable on the national forests because of management conditions. 
DESCRIPTION OF DATA. 
The study is based on 25 permanent sample plots, varying in size 
from 6 to 25 acres, totaling about 300 acres, on which over 13,000 
numbered trees have been measured at 5-year intervals from 1911 to 
1921. The attempt has been made to bring out the important points 
rather than to set down in detail the multitude of possible variations 
represented. For the sake of simplicity the reaction of individual 
trees is used as a basis for analysis wherever possible. The plots are 
located in the Sierra timber belt from near Mount Shasta to a point 
southwest of Mount Whitney. Sites vary from first to third quality 
(on a scale of five classes based on total height at maturity). The 
four more important types — pure yellow pine, yellow pine-sugar 
pine, mixed yellow pine-sugar pine-Douglas fir-white fir-incense 
cedar, and sugar pine-fir — are represented. Purely experimental cut- 
tings were not feasible. The plots, therefore, do not represent ideal 
site, type, or other factors. They were established just before or just 
after logging to represent the results of actual average marking 
practice of that period on the national forests. The marking was 
often based on a compromise between economic lumbering and silvi- 
culture. 
The areas were carefully mapped to show distribution of num- 
bered trees, stumps, cover, brush piles, etc. All trees 4 inches in 
diameter and larger were numbered with metal tags, diameters were 
taken in inches and tenths with a steel tape, and total heights and 
heights to base of crown to the nearest foot with a Klaussner hyp- 
someter. A detailed description was made of each tree, giving its 
dominance class, width of crown, color and density of foliage, form 
of top, presence of mechanical injuries or pathogenic agencies, and 
a rough estimate of age and apparent vigor. Reproduction data 
were secured from subplots, in the form of permanently marked 
continuous strips 0.1 chain wide, or a series of mechanically located 
quadrats varying in size from 5 feet to 1 chain square. In some cases 
