An Ecological Classification Proposal and its Importance in Land Measurement 
MC HALE: 
The two classification systems for American 
vegetation have opposing philosophies: Poly- 
climax community grouping (Daubenmire 
1952) and the continuum (Bray and Curtis 
1957). These philosophies will be briefly dis- 
cussed in relation to a proposed climax contin- 
uum philosophy. 
PHILOSPHIES 
Polyclimax.—The polyclimax concept states 
that various combinations of soil, topography, 
and climate create numerous environments. 
Within each environment, a plant community 
will eventually maintain itself in a reasonably 
stable state (climax) if some part of the envi- 
ronment does not change. Also, plant species 
tend to be naturally grouped according to their 
similar ecologic amplitudes; therefore, plant 
communities tend to be repeatable within a ge- 
ographic area. Consequently, these various cli- 
max plant communities may be classified into 
groups called habitat types or plant associa- 
tions. Thus, these associations may then be 
considered a reflection of the environment 
(Daubenmire 1955). 
Classification is generally accomplished as 
follows: First, a study area is thoroughly eval- 
uated for climax vegetation using reconnaiss- 
ance techniques. Next, the plant communities 
are classified into habitat types or associations. 
Then, modal climax plant communities repre- 
senting each association are intensively sam- 
pled. Selection of these modal communities is 
based on the observer’s opinion of how well 
they represent an association. As a result, po- 
lyclimax community grouping produces habitat 
types or associations described according to 
modal qualities. The classification recognizes 
variation within modes, transitions between 
modes, and ecotones between plant communi- 
ties where the environment changes abruptly. 
Continuum.—The concept of climax is sel- 
dom applied or considered in this philosophy. 
The continuum philosophy states that no two 
plant species have exactly the same ecologic 
amplitude; rather, each species has its own 
unique amplitude. Soils, topography, and cli- 
mate tend to occur in continually variable com- 
binations. Interactions of environments and 
different plant amplitudes produce continually 
variable plant communities which do not re- 
peat themselves throughout the landscape. 
Thus, plant communities cannot be classified 
into groups (Bray and Curtis 1957). 
*Range Conservationist, USDA Forest Service, Pa- 
cific Northwest Region, Portland, Oreg. 
210 
Classification is generally accomplished by 
sampling any stand that does not exhibit obvi- 
ous, recent disturbance. As a result, both suc- 
cessional and climax vegetation are often in- 
cluded in the data and the classification. Con- 
tinua in successional vegetation have been 
clearly demonstrated in range, wildlife, and 
timber management. For instance, one kind of 
successional pattern in species dominance and 
composition will occur if a plant community is 
overgrazed by cattle; the same plant commun- 
ity will exhibit a different successional pattern 
if overgrazed by sheep; a still different succes- 
sional pattern will be evident if the community 
is overgrazed by elk; and a foruth successional 
pattern might characterize overgrazing by 
deer. Thus, many successional continua are 
possible for a given climax community. If these 
successional gradients are indiscriminately 
combined with climax vegetation, a continuum 
ordination of existing vegetation is imperative. 
The need for such an ordination may be the 
most severe objection to present application of 
continuum philosophy. 
PROPOSAL: CONTINUUM IN CLIMAX 
A modification of both philosophies is pro- 
posed, that of a continuum in climax veg- 
etation which is characterized by acceptance of 
the following: (1) The climax concept; (2) 
continuum tendencies in climate, soils, and geo- 
morphology; and (8) differences in ecologic 
amplitudes of plant species. Several qualifica- 
tions distinguish this concept from the contin- 
uum concept. First, separation of climax and 
seral continuum gradients is essential for such 
management problems as range condition and 
trend evaluation, silvicultural guides, and field 
application of research results. Second, abrupt 
changes in environment will result in abrupt 
changes in plant communities. Third, ‘‘complete 
continua gradients” may not always exist; in- 
deed, they may seldom exist in the mountainous 
West. 
The following examples should clarify the 
climax continuum philosophy. Slope exposure 
continua may be illustrated using a conical hill 
(such as a cinder cone). Vegetation on the 
south slope might be Agropyron/Poa, which 
changes abruptly at the crest to the north 
slope Festuca/Agropyron. As one moves from 
midsouth slope on the contour toward mid- 
north slope, he should encounter a continuum 
gradient where the two plant communities, 
soils, and microclimates intergrade. This “coni- 
cal hill” is seldom encountered; however, an 
