NATURAL REPRODUCTION AFTER FOREST FIRES IN 
NORTHERN IDAHO 1 
By J. A. Larsen, 
Northern Rocky Mountain Forest Experiment Station , Forest Service 
INTRODUCTION 
This study of natural reproduction 
following some of the largest and most 
destructive forest fires in northern 
Idaho was made, in 1923, with the 
object of discovering in what way and 
to what relative extent the several 
species of conifers reseed the ground, 
and to learn what factors, such as 
intensity of the fire, differences in site 
or stand conditions, or seed production 
of the forest, affect natural restocking. 
In the fall of 1923 studies were made 
on large burns on the Coeur d’Alene 
National Forest—on areas burned only 
once, which was in 1910, and on areas 
burned twice at different intervals by 
fires which occurred in 1870, 1889, 
1910, and 1919. 
FIRE HISTORY 
BURN OF 1870 
The earliest large burn studied 
occurred about 1870. This burn killed 
approximately 3,200 acres of mature 
timber on Trail Creek and its tributary, 
Bear Creek, a mile or so to the west of 
Magee Ranger Station. (See fig. 1.) 
The numerous groups of seed trees 
which still exist on the higher points, as 
well as the comparatively small area 
burned, strongly indicate that condi¬ 
tions were not so arid nor the fire so 
intense and destructive as in the burns 
of 1910 and 1919. The Trail Creek 
area reseeded quite generally after the 
1870 burn, but the stand that followed 
was almost completely killed in 1910. 
Here opportunity was afforded for 
a study of reproduction after fire had 
destroyed a young 40-year stand. 
BURNS OF 1889 AND 1910 
A later burn of greater consequence, 
that of 1889 on the Deep Creek area, 
covered the upper south and west 
slopes along the Idaho-Montana divide. 
This was part of a very general fire 
which originated near Pend Oreille 
Lake and swept large areas in the Clark 
Fork Valley to the north. These areas 
reproduced well but burned again in 
1910, leaving very little inflammable 
material, so little in fact as to prevent 
the 1919 fire from crossing over into 
Montana. The coincidence here of the 
1889 and 1919 burns permitted the 
study of natural reproduction following 
the destruction of a 30-year stand. 
The large and very destructive fire 
of 1910 occurred about August 20. It 
began in the Magee district and swept 
in a path 7 to 9 miles wide and 18 
miles long to the Idaho-Montana 
divide. The destruction was quite 
general and complete. Only here and 
there on bottoms, lower north slopes, 
high points, or on very rocky sites did 
groups of trees survive. The most 
clear-cut cases of single 1910 burns 
were studied on Alder Creek. 
BURN OF 1919 
The large fire of 1919 made a fairly 
complete clean-up of the dead material 
left by the 1910 burn, covering high 
and low points alike. It stopped when 
it reached the upper south slopes of 
the Idaho-Montana divide, laid bare 
by the two earlier fires of 1889 and 
1910. Opportunity was afforded here 
for a study of natural reproduction 
following a very large and intense 
double burn, on a thousand acres of 
which there remained not one live 
tree. In two other sections with large 
open north and south aspects only a 
few isolated groups of green trees sur¬ 
vived both fires. 
CHARACTERISTICS OF BURNED 
AREAS 
The study as a whole gave evidence 
of certain outstanding typical condi¬ 
tions which appear and reappear on 
different parts of large burned areas 
and which are due to similarity of 
slope, aspect, and elevation. That is, 
where the topography is similar the 
results from burns are similar, provided 
1 Received for publication June 30, 1924, issued July, 1925. 
Journal of Agricultural Research, 
Washington, D. C 
( 1177 ) 
Vol. XXX, No. 12 
June 15, 1925 
Key No. F-31 
