48 CIR. 211, U. S. DEPT. OF AGRICULTURE 
ence of herbaceous and shrubby range vegetation and 
its use by livestock on soil erosion, irrigation, domes- 
tic water supplies, floods, and the production of hydro- 
electric power; the correlation of grazing with satis- 
factory timber production; utilization of various 
forage species consistent with their proper main- 
tenance and adequate reproduction; artificial reseed- | 
ing to cultivated and native forage plants; the forage 
values, life histories, and requirements of range 
plants; range livestock management, including sys- 
tems of handling different classes of stock, water 
development, and salting, and their relation to the 
welfare of the range; the relation of available water 
for range livestock to injury to timber reproduction ; 
the relation of climate to plant growth and of plant 
succession to range management; and the eradication 
or control of poisonous plants. (Fig. 24.) 
NATURAL AREAS AND EXPERIMENTAL 
FORESTS AND RANGES 
Certain areas within national forests are designated 
as “experimental forests,” to be maintained perma- 
nently as outdoor laboratories for research in Silvi- _ 
cultural and other forest practices in each forest 
region. A supplemental series of areas known as 
experimental ranges is set aside for range investiga- 
tions. The Forest Service also has designated a series 
of “natural areas” sufficient in number and extent — 
adequately to illustrate or typify virgin conditions 
of forest or range growth in each forest or range 
region, to be retained in a virgin or unmodified condi- 
tion for purposes of science, research, historical inter- 
est, and education. Within the areas so designated, 
except for permanent improvements needed in experi- 
mental forests and ranges, no commercial use is 
allowed, and public use is carefully regulated. Use 
of the areas by other research or educational agencies 
for purposes which do not conflict with Forest Service 
projects is allowed under cooperative agreements. 
