soil were vertically stratified and had their 
own peculiar environment, which interacted 
with the larger complex. Horizontally, differ- 
ence in aspect, insolation, soil, and other physi- 
eal factors produced different but interacting 
subcommunities. Appreciation of ecological 
balance or homeostatis in ecological communi- 
ties was leading to fuller understanding of 
ecological complexes. Ecologists were also 
gaining a greater appreciation of the genetical 
basis for many events within biotic popula- 
tions. 
THE ECOSYSTEM CONCEPT 
Earlier ecological workers were cognizant of 
the multiplicity of environmental factors af- 
fecting the growth, reproduction, and survival 
of individual organisms. It became increas- 
ingly apparent that not only a multiplicity of 
factors existed but that their interrelationship 
was highly complex (Daubenmire 1947). Al- 
though attention might be focused on any 
level, or group within a level, it was recognized 
that a larger ecosystem was involved. The eco- 
system approach visualized habitat, plants, and 
animals as one interacting unit, with materials 
and energies passing in and out of various as- 
pects of the entire system (Woodbury 1954). 
Odum (1953) succinctly defined the ecosystem 
ass 
“Any entity or natural unit that in- 
cludes living and nonliving parts in- 
teracting to produce a stable system 
in which the exchange of materials 
between the living and _ nonliving 
parts follow circular paths is an eco- 
logical system or ecosystem. The eco- 
system is the largest functional unit 
in ecology... .” 
Range ecologists recognized the importance 
of the ecosystem concept in vegetation com- 
munity processes and related management 
problems. For example, it was recognized that 
management which regulates kind and num- 
bers of livestock, predator-control programs, 
noxious-plant control, reseeding, and fire con- 
trol modifies the ecosystem (Humphrey 1962). 
Such an outlook broadened ecological research 
and enhanced subsequent management (Cos- 
tello 1957). 
Mathematical models and high-speed com- 
puters are now being employed to sort out and 
evaluate the multitudinous factors comprising 
range ecosystems. As biological and physical 
components of the ecosystem are measured, 
simulation models are designed to provide spe- 
cific answers to highly complex problems. By 
doing this, many realistic assumptions are han- 
dled simutaneously so that alternative out- 
comes or products are provided. Many hypo- 
202 
thetical constraints are tested without long, 
costly field investigations. Furthermore, simu- 
lation analysis often provides insights for ad- 
ditional field investigation. 
Limitations to ecosystem analysis of ecologi- 
cal problems must also be recognized. Defini- 
tion of ecologically natural units poses a real 
problem (McIntosh 1963). Discrete ecological 
units, as evolving entities, may even not exist. 
Until natural units can be demonstrated in 
terms of genetics and evolution, inherent limi- 
puns are posed by complexities of ecosys- 
ems. 
FUTURE ECOLOGICAL RESEARCH 
Numerous areas of research in range ecology 
should be strengthened to provide pertinent in- 
formation for forage management of range- 
lands in the West. Such information seems 
especially desirable in view of the current at- 
tention being given to ecology in relation to 
man and to improvement of the quality of 
man’s total environment. 
Costello (1964) has suggested that range 
ecology research could be intensified in the 
areas of: Basic studies of soils, physiology, and 
ecology; development and improvement of 
methodology; and the investigation of predict- 
ing equations. Knowledge of plant chemistry 
and physiology in relation to herbage removal 
is incomplete for understanding the reaction of 
the plant to the grazing animal. Many birds, 
mammals, reptiles, amphibians, and inverte- 
brates are found on rangelands, but there are 
few studies of range wildlife besides those of 
game and rodents. Studies of micro-organisms, 
insects, and diseases on rangelands are almost 
nonexistent. Utilitarian-oriented studies are 
needed; these should emphasize relations 
among these organisms, the grazing animals, 
and the plant and soil. 
Public concern is stimulating scientific inves- 
tigation of the effects of herbicides and pesti- 
cides on the range biota. However, range ecolo- 
gists are devoting only minor effort to this field 
of research. 
Telemetry is another important tool for in- 
vestigating ecological problems—particularly 
animal movements on a daily, seasonal, or peri- 
odic basis (Hawkins and Montgomery 1969). 
Cloud seeding still has realistic possibilities 
of inducing weather changes to benefit man. 
Profound changes in natural flora and asso- 
ciated fauna may result, and range ecologists 
should be prepared to state where and where 
not weather modification will benefit their in- 
terests (Battan and Kassander 1962). 
For many years the USDC, ESSA, Weather 
Bureau has monitored climatic conditions in 
the United States, but biologists have been lax 
in monitoring biotic communities over long pe- 
riods. Studies are needed that monitor the en- 
