TheImprovement ofTropical and Subtropical Rangelands

SITE EVALUATION 107
macbiuery at less cost. Iuvestigation has shown that the cost of
ground preparation rises sharply on slopes that exceed 20 percent
and is generally uneconomical.
Measures of landform and relief of a Bite can be obtained from
topographic maps, if they are available. On site, aspect is normally
determined with a comp..., and slope is measured with an Abney
hand level (or pocket altimeter). Aspect and slope can be "integrated-
into a single measure ofsite orientation through WIe of daily
solar radiation values for explicit combinations of aspect, slope, and
latitude (Buffo et al., 1972; Frank and Lee, 1966).
Water Resources
Range improvement projects or programs on semiarid and arid
lands are highly dependent on the distribution and availability of
water to meet the water requirements of individual plant and animal
species. The seasonal availability of surface water resources must be
inventoried in terms of surface flows and impoundments, and seeps
and springs. Locations of existing wells and promising groundwa.­
ter aquifers (for subsequent development) should also be studied.
In general, estimates of potential yields and (as mentioned below)
quality of water resources may be nece88&ry in comprehensive range
improvement.
Water quality, both physical and chemical, must be considered
in the evaluation of a site if, as part of a revegetation effort, artificial
watering is required. Individual plant species possess their
own "tolerances" to the physical and chemical properties of water.
Therefore, when water is to be applied, these properties should be
known to maximize the benefits and minimize the detriments of the
watering.
Sampling and analytical techniques of UBeBsiug water quality are
numerous. However, to ensure high-quality results, a prerequisite to
the extrapolation of water quality information, only "standardized"
methods should be employed. These methods are detailed in Conant
et al. (1983), Dunne and Leopold (1978), and Wisler and Brater
(1965).
Biotic Compcm.entl
Plants, animals, and humans comprise the biotic components of
a site. The importance of theee componeuts and ways of measuring
them are discussed below.