and Paulsen (1955) concluded from intensive 
studies of the factors affecting reproduction 
and establishment of velvet mesquite that this 
shrub is well adapted in southern Arizona for 
further spread into adjacent grassland areas. 
Planned burning of sagebrush-grass ranges 
was found to reduce sagebrush and to be ulti- 
mately beneficial to shrubs with strong sprout- 
ing habit and to grasses and forbs with rhizo- 
matous growth habits (Blaisdell 1953; Pe- 
chanec et al. 1954). However, nonsprouting 
shrubs, suffrutescent forbs, and some of the 
finer bunchgrasses were found to be injured se- 
verely by fire. 
Range condition—Knowledge of primary 
and secondary successional trends proved espe- 
cially important for classifying different vege- 
tation sites in relation to space and time (Cos- 
tello 1956). Parker (1954) proposed that each 
range condition class could and should corre- 
spond to a stage or group of stages in second- 
ary plant succession. Ellison (1959) observed 
that trends in secondary succession could be 
reversed by skillful management where the 
soil mantle was still intact and where a seed 
source was available. In a literature search, 
Ellison (1960) was unable to find substantive 
evidence that plants were dependent upon ani- 
mals in the ecosystem. In fact, he concluded 
that the evidence favored parasitism of plants 
by animals, even though the evolution of mod- 
ern grazing animals coincides with the evolu- 
tion of grasses (Taylor 1949). 
Timber-livestock-wildlife relations —Compe- 
tition between cattle and deer was recognized 
on the North Kaibab (Julander 1937) and led 
to cooperative studies by the USDA Forest 
Service, the USDI Fish and Wildlife Service, 
and the Utah Game and Fish Department. Ju- 
lander (1955) found competition for forage be- 
tween deer and cattle varied by specific sites. 
Deer were able to utilize large areas that were 
inaccessible to cattle because of steepness of 
slope and unavailability of water and forage. 
Desirable forage, exposure, and cover largely 
limited deer distribution in midwinter. 
On range used by antelope, Buechner (1950) 
found that the most important factor affecting 
the increase and distribution of antelope was 
intense food competition with domestic sheep. 
Competition between cattle and antelope was 
only slight, and antelope appeared to prosper on 
cattle ranges. 
Leopold et al. (1951) and Longhurst et al. 
(1952) contended that herd regulation was the 
first step in deer management, and that range 
improvements were applicable to some deer 
habitats. Biswell et al. (1952) found that 
planned fire could be used to improve chapar- 
ral habitat for deer. Later, Taber and Das- 
mann (1958) reported that food quality is the 
main factor limiting most chaparral deer popu- 
lations, and that habitat improvement should 
focus on the introduction of winter forage and 
the quantitative increase of existing palatable 
browse. 
In the Southwest, Reynolds (1964) found 
that conservative, selective logging improved 
deer habitat. Also, deer used pinyon-juniper 
woodland in proportion to palatable shrub den- 
sity; by reducing tree overstory to enhance 
shrub production, habitat conditions for deer 
could be improved. 
Most studies of rodent-range relations dur- 
ing this period showed that pocket gopher con- 
trol was necessary for improvement of moun- 
tain ranges (Moore and Reid 1951; Colorado 
Cooperative Gopher Project 1960). On Califor- 
nia annual grasslands, Howard and Childs 
(1959) found fewer gophers on grazed pas- 
tures at the San Joaquin Experimental Range 
because of insufficient food and cover. 
On mesquite-snakeweed sites of southern 
New Mexico, rodents and rabbits alone exerted 
sufficient grazing pressure to preclude vegeta- 
tion improvement (Norris 1950). Control of 
these animals was necessary for range im- 
provement but was unjustified economically. 
For desert grassland ranges of southern Ari- 
zona, Reynolds (1958) found that where graz- 
ing was so heavy it lowered perennial grass 
density, the number of Merriam rats increased. 
CONCEPTUAL REFINEMENTS 
By 1960, basic ecological concepts had _ be- 
come widely adopted in range and wildlife hab- 
itat management and research. Dyksterhuis 
(1958) summarized the state of knowledge rel- 
ative to range ecology: By 1960, ecologists had 
become increasingly aware of energy path- 
ways. Utilization of energy was known to af- 
fect food chains, which, in turn, affected the 
numbers and kinds of animals associated with 
rangelands. Reproduction mechanisms were 
recognized as basic to all ecological systems. In 
addition to their function in transmitting he- 
reditary characteristics, evidence was accumu- 
lating that population density, quality of food, 
and other environmental factors also affected 
reproduction. Competition was credited as 
being a potent force that gave expression to an 
ecological community. 
There was an awareness that the physical 
and biotic factors of the environment were in 
dynamic equilibrium in natural communities. 
It became more fully accepted that fire was an 
environmental influence which supported the 
evolution and maintenance of some grasslands. 
Stratification as a structural characteristic of a 
community in both vertical and horizontal di- 
mensions was better understood; i.e., a woody 
overstory, half shrubs, herbaceous plants, 
moss, lichens, and microfauna and flora of the 
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