TheImprovement ofTropical and Subtropical Rangelands

80 IMPROVEMENT OF TROPIOAL AND SUBTROPIOAL RANGELANDS
set of individual maps and reports. Field expell8el!l are reduced by
combining activities, and mapping consistency and analysis quality
are improved by complementary collaboration.
The landscape or land systems approach to resource lIIIe8IIIlent
wu develoPed and applied first in Australia after World War n. The
problems faced there were not unusual: large areas ofthe country had
to be surveyed quickly and accurately to determine their agricultural
potential. This highly successful approach is still used in Australia.
Comparable approaches have been develoPed by other countries in
many parts of the world for agricultural, military, and engineering
purposes. In the following discuaions, the Australian terminology is
employed.
The land systems approach has a hierarchical structure of units
(figure 4-1). The smallest unit of land recognized is the land element.
It is defined primarily by slope, and is essentially homogeneous in
all properties, corresponding to the concept of "site." Because of its
limited extent, it is never mapped at the resource assessment level,
but rather is the primary focus of site evaluation, as described in the
following chapter. The next largest unit of land is the land facet,
which consists of a set of related land elements, commonly on the
same landform. It is seldom mapped in a resource UIe8Iment. The
land system is the largest unit, and consists of geomorphologically
and geographically aasociated patterns of land facets. The land
system is the most commonly used mapping unit in this approach
and is well suited to the general purposes of the resource assessment.
Archival Research
JDrormatlcm Ac:qulaltlcm Metbodl
A search of archival sources of information is done at the beginning
of the project to gather the work that has been done to map and
describe land characteristics of the region. This avoids a duplication
of previous work, and builds on the experience and insights of other
workers in the region.
Published information on land characteristics exists for essentially
all parts of the world. The types of information that can be
found include maps and descriptions ofclimate, soil, and vegetation.
Most of this information is extremely small in scale (for instance,
world or regional maps produced by the United Nations Food and
Agriculture Organization). Although continental-scale maps are not
suitable for a final assessment, they are a useful starting point.