strongly to remain on the site for the resource 
analyst to read, once he has discovered what 
they are. 
(3) Successful application of vegetation in- 
dicator concepts in determining soil conditions 
and site quality requires that vegetation-soil 
relationships be studied at the same point im 
space and time. 
(4) “Site potential,” a concept of great prac- 
tical importance to managers of vegetation and 
soil resources, is a function of the inherent 
ecological characteristics of the land plus re- 
source use and management intensity. Inter- 
pretations of site potential, therefore, properly 
follow acquisition of basic resource information. 
Procedural Concepts and Principles 
It is important for users of intensive ecologi- 
eal resource analysis information to under- 
stand the differences among (1) management, 
(2) taxonomic, and (3) mapping units. Lack of 
such understanding results in confusion both 
in making and using resource maps for plan- 
ning and for management decisions. 
Users of this information sometimes consider 
resource maps too intricate and too detailed 
because they do not understand the difference 
between management units and mapping units. 
They sometimes declare that mapping should 
be done in units that managers believe are 
of a practical size. Some managers apparently 
do not realize that the only purpose of the 
mapping unit is to convey information. No 
inference is intended that the separately de- 
limited areas should be managed differently 
and thus that mapping units must be large. 
The management unit is determined by the 
resource manager, not the analyst. It defines the 
physical area to which a particular program of 
management practices is to be applied. It nor- 
mally will encompass several mapping units 
which, together with their legend, describe the 
characteristics of the management unit and 
provide the manager with the understanding 
of the resources that he needs to make wise 
decisions in matching practices to the land. 
The phytosociological classification units 
mentioned in the previous section need to be 
differentiated from the various kinds of map- 
ping units that are delineated in order to 
convey information about the resource. The 
basic unit of the landscape for classification 
purposes may be referred to as a taxonomic 
unit. For purposes of this presentation, it is the 
fundamental ecological. unit corresponding to 
the collective area of similar effective environ- 
ments. These are denoted by the high degree 
of similarity in the plant communities that oc- 
cupy each representative area. 
The mapping unit, on the other hand, is the 
area delineated on a map, aerial photography, 
or mosaic to represent one or more taxonomic 
units and to convey only information about the 
landscape. There are two kinds of mapping 
units. Simple mapping units delimit only one 
taxonomic unit with or without allowable in- 
clusions (fig. 3A). A complex mapping unit 
delimits two or more taxonomic units occurring 
in such an intricate pattern that they cannot 
be practicably separated into simple mapping 
units at the mapping of final compilation scale 
(fig. 8B). Either kind of mapping unit may 
contain inclusions or fragments of other tax- 
onomic units that are too small to be mapped 
separately, and these are ignored because they 
comprise less than a specified percentage (us- 
ually 10 to 20 percent) of the delineation as 
mapped (fig. 38C). 
FIGURE 3.—This stereo mode] illustrates the primary 
kinds of mapping units. 
Our work has led to the development of a set 
of universally applicable ground rules for in- 
tensive resource analysis that set our proce- 
dures somewhat apart from common practices 
in range surveys. These ground rules will re- 
sult in more easily understood and more read- 
ily applied resource analyses: 
(1) Strive always to delineate simple map- 
ping units where cartographically feasible. 
(2) Strive to hold complex mapping units to 
two components (taxonomic units) per delinea- 
tion. Three components are allowable. Four 
can usually be avoided by proper consideration 
of delineation alternatives. 
(3) Treat complex mapping units by sepa- 
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