Forb increase predominated when the canopy 
exceeded the 40- to 45-percent level. Browse 
was slower in responding to overstory thin- 
nings. 
However, digestibility of forage was not di- 
rectly related to the basal area of overstory 
ponderosa pine in Arizona (Pearson 1964). 
Terminal parts of the forage were consistently 
more digestible. 
Mechanical Treatment of Brushland.—In 
parts of the country—notably in California 
and the desert Southwest—dense brushland 
types over wide areas are literally impassable 
to big-game animals. Control of dense chapar- 
ral serves to provide space for animal move- 
ment as well as to increase the abundance and 
nutritional quality of low-growing forage. 
Type conversions in the chaparral are often 
justified as multi-functional projects. In Cali- 
fornia, many of the projects have been carried 
out to create fuel breaks to facilitate fire con- 
trol, to improve watershed conditions, and to 
increase forage for livestock and wildlife. 
Taber (1953) determined that chaparral 
density significantly influenced black-tailed 
deer reproduction. Forage quality was highest 
where chaparral was interspersed with herba- 
ceous vegetation and with burned-over areas. 
It was poorest in mature, dense chaparral. 
In Arizona, the better mixed chaparral 
ranges carry 20 to 80 deer per square mile. On 
dense chaparral, deer stocking averages 4 to 5 
deer per square mile. Plant composition is the 
principal factor accounting for this difference; 
few species with lower levels of nutrition are 
generally found on the poorer quality ranges. 
Chaining, railing, beating, and plowing are 
forms of mechanical treatment of brushland 
used to improve forage quality and the carry- 
ing capacity of the range. In Arizona, Swank 
(1958) found that sprouts from railed shrubs 
had much greater moisture content during 
April and July, compared with those on un- 
disturbed sites. Growth of sprouts followed a 
pattern similar to that of moisture content. On 
railed sites, sprouts grew vigorously from 
early April to the middle of August, while non- 
railed shrubs ceased growing in May. Use by 
deer and cattle coincided with high moisture 
content and rapid sprout growth, indicating 
that forage quality was definitely a factor. 
In Utah, dense juniper forests with very lit- 
tle understory herbage have been successfully 
converted to productive ranges for both deer 
and livestock. This was done by chaining to 
AGES trees and then seeding (Plummer et al. 
: Mechanical treatment of shrubs as a range 
Improvement practice for both deer and cattle 
has, perhaps, its greatest application in the des- 
ert Southwest, where competition for soil 
moisture is often critical. Because of relatively 
high costs per acre, projects usually are econ- 
omically justified only when multiple benefits 
accrue. 
Herbicide Treatment.—The use of herbicides 
as a tool of management affects wildlife in a 
number of ways. On the positive side, herbi- 
cides have been put to good use on Idaho big 
games ranges to top-kill tall brush and to in- 
duce basal sprouting. Wild-fire, some 60 years 
ago, burned vast areas of conifers; these areas 
were subsequently invaded by various shrub 
species—predominantly tall willows. 
Elk herds soon responded to the new forage 
crop. Much of the brush has now grown be- 
yond reach of big game and has been high- 
lined. As a result, the carrying capacity of the 
range is reduced, and, unless effective meas- 
ures can be applied, elk herds must be sus- 
tained at lower population levels. Trials in the 
use of herbicides have shown great promise in 
top-killing tall brush to produce succulent 
sprouts at the root crown. 
Herbicide treatments of cattle range on 
Black Mesa, Colo., (Tietjen et al, 1967) have 
shown remarkable results in another way. Ap- 
plications of 2,4-D initially reduced forb abun- 
dance by 80 to 90 percent. This was immedi- 
ately followed by a similar reduction in pocket 
gopher populations. These gophers could not 
survive where their preferred food was elimi- 
nated by herbicide treatment. It was deter- 
mined that common grasses provide only a 
marginal diet for gophers. 
Another example of the: adverse effect of 
herbicides on wildlife has been indicated in 
feeding studies of grouse in southeastern Idaho 
(Klebenow and Gray 1968). The most impor- 
tant food plant during the young grouse’s first 
week of life was Harkness gilia. After the first 
week, common dandelion and loco made up 
most of the diet of young grouse. Obviously, 
spraying of sagebush with herbicides, which 
kills most of the forbs, could seriously reduce 
grouse production. This points up the need to 
reserve dispersed, untreated blocks of sage 
type on important grouse habitat when range 
improvement programs are planned. 
Herbicides are often used to curb new 
growth of shrubs on chaparral areas pre- 
viously cleared by mechanical means. Seedlings 
and new sprouts are vulnerable to herbicides, 
whereas the large, mature shrubs cannot be ef- 
fectively controlled by this means. 
Pruning and Hinge-Cutting.—The top-prun- 
ing of browse is a form of mechanical treat- 
ment of tall-growing shrubs used to induce 
growth from lateral buds. Bitterbrush, for ex- 
ample, exhibits the characteristic of apical 
dominance. It responds to top-pruning by de- 
velopment of lateral buds. 
27 
