TheImprovement ofTropical and Subtropical Rangelands

74 IMPROVEMENT OF TROPICAL AND SUBTROPIOAL RANGELANDS
• To establish the relative importance of each area according
to the objectives of the projectj and
• To develop a realistic plan of action based on the &lII888ment.
Maps and supplementary reports are the products ofthe resource
&llel8ment. The maps show the location and extent ofdifferent types
of land in relation to other lands. Because a general overview is
required, map scales are commonly smaller than 1:100,000.
In the mapping phase of a resource assessment, the region is
surveyed and divided into areu that are relatively homogeneous in
some property such as vegetation, soil, or land use. At the scales considered
here, however, only broad patterns can be mapped. Mapping
units will be somewhat heterogeneous and will contain a number of
different site types. An important purpose of the report is to relate
this diversity by describing the nature and composition of the
mapping units.
Mapping units are not necessarily predefined and may be designed
to meet the needs of a project. These mapping units will
become the physical units around which the study project is organized
and probably will become the units used for many future land
management decisions. Thus, criteria used to define basic mapping
units must be carefully selected. In a resource &lII888ment for range
improvement, units should contain areu that (1) have about the
same capacity to sustain one or a set of land uses, and (2) require
similar kinds of management. This characteristic of land is generally
called "land capability· and is determined by a number of factors,
such as climate, vegetation, wildlife, and soil.
Cllmate
Climate is perhaps the most important factor in determining land
capability because of its direct impact on the immediate resource,
such &8 forage, and its role in determining the types of vegetation
and soil found in a region.
The climatic data required for a resource &8Iel8IDent are those
that influence the development of soil and the distribution of vegetation.
Average annual temperature, seasonal extremes, frost-free
period, evaporation, and precipitation amounts and their seasonal
distribution are the most important considerations because they help
determine soil type, water availability, vegetation type, and potential
plant productivity.
Although climate is important in determining land capability,