TheImprovement ofTropical and Subtropical Rangelands

76 IMPROVEMENT OF TROPICAL AND SUBTROPICAL RANGELANDS
Landform
Landform is the feature commonly used to unify or provide a
framework for the mapping aspects of the resource assessment. In
most cases, landform is the most readily mapped feature of the landscape,
and it is frequently correlated with other, less easily observed
features, such u hydrology or lIOil. Not surprisingly, lIOme vegetation
types within the region may be consistently &IlIOCiated with a particular
lIOil. Thus, an understanding of regionallandform-soil-vegetation
relationships is a powerful and necelBary tool in developing the physical
base of a resource UlellIDent. An analysis of information on
landform provides a general framework for survey while indicating
lIOme of the areu that might be especially susceptible to erosion.
These areu would warrant special attention in a range iI:llprovement
project.
SoDs
Along with climate, lIOil type ultimately determines land capability.
At the resource 8IIe8Iment level, however, only general soil
information is gathered. This includes lIOil texture, lIOil morphology
(that is, depth and presence of limiting horizons), general lIOil
chemistry, and susceptibility to flooding or erosion. Ideally, many
lIOil properties can be inferred from climate, landform, slope, and
existing land use.
Soil types are not mapped at the resource use.ment level unless
the environment of the region is very simple. More typically, natural
groupings of lIOil types, such u lIOil &IlIOCiations, are mapped.
Although lIOil types are not mapped, descriptions of them are acquired
to portray the range of conditions that will be found within
the broader mapping unit.
Water
Delineation of watershed boundaries, major drainage lines, and
other hydrologic features (for example, dry lakes) can help develop a
general hydrologic framework of the region; it can also help facilitate
the interpretation of landforms and soils, and can provide a general
view of the likely distribution of water resources.
In most arid and semiarid regions, the distribution and quality
of surface and near-surface water in an area will restrict the number
of options for range improvement and subsequent management, and