WHITE PINE UNDER FOREST MANAGEMENT, 15 
may not mark a heavy seed production over the entire range of white 
pine, and a "seed year" may occur in some localities simultaneously 
with an ' 'off year ' ' in others . Local conditions of soil and climate have 
great influence on the frequency of seed years. Scarcity of water 
stimulates seed production in most plants, and it is quite possible 
that fluctuations in soil moisture may have some influence on the 
frequency of seed years of white pine. * In off years not only is less 
seed produced, but the ravages made upon the supply by birds and 
rodents is more keenly felt. Insect damage, too, is concentrated, so 
that a small crop is likely to be one of low quality as well. Even in 
off years, however, seed production in some localities may be fairly 
plentiful. 
The relatively long intervals between seed years put white pine at 
a disadvantage, compared with trees which bear heavy crops more 
frequently. Several of the broadleaf species bear seed abundantly 
each year, and when these are shade-enduring trees with heavy 
crowns they are often able, in company with underbrush, completely 
to cover a cleared area, and so prevent white pine from obtaining a 
foothold. In the Lake States, jack pine, which nearly every year 
bears abundant crops of small, winged, fertile seed, is able to monopo- 
lize cleared areas, practically to the exclusion of white pine. 
Seed Distribution. 
The chief agent of distribution of white pine seed is wind. Trees 
standing on high, windy slopes and ridges may shed their seeds to a 
distance of half a mile, or even more, over the adjoining lowland. In 
valleys the range of seeding is very much less. On level land the 
distance to which seeds will be carried in any number, when unob- 
structed by crowns of other trees, is usually between 100 and 200 
feet. Reproduction, of course, is densest and most even-aged near 
the mother trees. Where abandoned fields or pastures adjoin white 
pine woodland, dense even-aged stands of pine are almost sure to 
develop, the stand becoming more open as its distance from the seed 
supply increases. When seed trees are left well distributed on a cut- 
over area, a fully stocked, even-aged second growth may often be 
established after one or two full seed years (PI. IV, fig. 2) . When seed 
trees are scarce or poorly distributed, complete restocking may require 
a much longer time, or the result may be that other species, possibly 
undesirable ones, will come in with the pine. From 5 to 10 good seed 
trees per acre are usually sufficient to give a close, even-aged stand of 
second growth. The number should never be less than 3 or 4, selected 
with reference to the direction of the prevailing wind. 
1 Height and Dominance of the Douglas Fir, by T. C. Fry. Forestry Quarterly, vol... 8, Nq. 4, p. 467. 
