June 14, 1924 
Factors Affecting Reproduction after Logging 
1151 
moisture and shelter such as Rubus strigosus , Lonicera utahensis, Linnaea borealis 
americana , Spiraea lucida, Ceanothus velutinus , Salix scouleriana and a great 
many grasses and sedges frequently found in the more open western yellow pine 
(Pinus ponderosa) and Douglas fir ( Pseudotsuga taxifolia) stands. 
This change in the physical condition of the site, brought about by clear 
cutting of the forest, has been observed by the writer in numerous instances 
over a period of years. Such clearings ordinarily show poorer natural restocking 
of western white pine and other moisture-loving species compared with north 
and east aspects; also relatively fewer seedlings in the presence of heavy sod and 
dense weeds than under partial shade or among lighter vegetation. On one 
s uch recently clear-cut flat the seedlings which germinated from seed in the duff 
were counted for three consecutive years. These showed a mortality of about 50 
per cent, although they had no weed or grass competition. Numerous counts 
and observations, made on large clear-cut areas from eight to twelve years follow¬ 
ing cutting, show natural reproduction at a standstill except where sheltered by 
the border of the uncut timber. What takes the greatest toll of young seedlings 
and creates the most critical physical barrier to natural reproduction on large 
clearings and south and west aspects in northern Idaho is the fact that the pre¬ 
vailing and desiccating westerly winds in summer always strike the warm and 
sunny places. Naturally this hindrance, by exposure, drought, competition, 
and dense vegetation, becomes more acute and more dangerous to natural 
regeneration on sites with poor soil and on southerly exposures than on sites 
with deep, moist soil or on northerly aspects or in small sheltered spots such as 
result from partial cutting of the forest. The influence, therefore, of large 
clearings on flats and sunny slopes is often to defeat altogether the reestablish¬ 
ment of western white pine and other moisture-loving species. 
INFLUENCE OF SURFACES ON GERMINATION AND SURVIVAL 
To test out the influences of the different kinds of surfaces such as ordinarily 
are found on a logged area, seven seed beds, each 4 feet square, were sown with 
western white pine seed in the fall of 1918. The tests embraced surfaces of ashes, 
fresh soil, charcoal and ashes, wood and duff charcoal, partly burned, and unburned 
surfaces. Each bed contained 2,000 fresh white pine seeds and was protected 
from birds and rodents by proper screens. The ash surfaces were the result of 
brush burning and the bare soil surface was prepared by raking off the needles, 
duff, and humus layer. In all cases the seed was sown without raking it in. The 
results are given in Table III. 
Table III.— Germination and survival of western white pine on different surfaces 
(Sowing of 2,000 seed per plot in the fall of 1918) 
Germination percentages by types of surface conditions 
Date of germination 
Un¬ 
burned 
deep 
: duff 
Partly 
burned 
deep 
duff 
Un¬ 
burned 
duff 
and 
de¬ 
cayed 
wood 
Mix¬ 
ture of 
char¬ 
coal 
and 
partly 
burned 
duff 
Bare 
loose 
soil 
Char¬ 
coal 
and 
ashes 
Deep 
loose 
ashes 
1919.... 
0.2 
4.9 
0.3 
0.6 
12.7 
10.2 
17.7 
1920... 
9.5 
53.9 
12.8 
9.9 
47.9 
28.7 
15.2 
Total...... 
9.7 
58.8 
13.1 
10.5 
60.6 
38.9 
32.9 
Percentage of survival 1921__ 
96.9 
100. 
53.4 
36.5 
48.2 
62.5 
95.8 
