Evaluation of abiotic and biotic components
A site evaluation focuses upon two broad sets of components:
nonliving (abiotic) components and living (biotic) components. Climate, soil,
landform and relief, and water resource are abiotic components; plants and
animals of all forms, including humans, are biotic components. The objectives of
the proposed range improvement project or program, the complexity of the
ecosystem being evaluated, and the completeness of the available relevant
knowledge will largely determine the intensity of the effort to be undertaken in
evaluating these abiotic and biotic components. Details of measurement and
sampling techniques may be found in Avery (1975), Bell and Atterbury (1983),
Brown (1954), Cain and de Oliveira (1959), Carmean (1975), Child et al. (1984),
Conant et al. (1983), Jones (1969), Lund et al. (1978), Lund et al. (1981),
National Research Council (1962) Schemnitz (1980), and Soil Resources Inventory
Reasons for evaluating specific abiotic components of a site are
discussed below. Techniques commonly used to quantify these components are
Climate can be defined as the total complex of weather
conditions and its average characteristics and range of variation over an
appreciable area of the earth's surface. Conditions over an extended period of
time are usually taken into consideration. weather in turn, comprises a set of
atmospheric conditions at a specified point in time and, therefore, refers to
events. Climate is basic to an ecosystem because of its significance in soil
development and plant productivity.
Climate is difficult to characterize, owing to frequent
deficiencies in the length and consistency of necessary meteorological records.
The climate of a site is most easily described from records of
the United Nations World Meteorological Organization or from data collected by
national weather offices. Unfortunately, many weather stations from which this
information is obtained are often poorly distributed, especially in semiarid and
arid lands of developing countries.
Precipitation Patterns The amount and distribution of rainfall
is important because of its role as a source of soil moisture. Survival and
subsequent growth of plants is, of course, closely tied to the availability of
water in the soil mantle. Rainfall, in itself, is usually of little direct
significance to plants, although there can be some absorption of water through
the leaves and, occasionally, the bark.
Although soil moisture is mostly derived from rain, not all of
the precipitation that falls on a site is equally effective in raising the soil
moisture content. The slower, more gentle a rainfall event, the greater the
penetration, or percolation, of water into the soil. However, a series of
precipitation events that totals only several millimeters may add little to the
soil moisture content, because the individual events are too widely separated
and too gentle to have a cumulative effect. The more severe a drought,
especially in dry climates, the greater the quantity of rain required
subsequently to alleviate the drought.
Reliable measurements of rainfall are most commonly acquired
from networks of rain gauges. There are many types (for example, standard,
recording, and totalizer), and dimensions of rain gauges, but they all consist
essentially of a funnel with a vertical collar that delivers water to a
collecting reservoir. Only precipitation records obtained from gauges located
away from eddies caused by physical obstructions should be used in a site
evaluation. As a general rule, obstructions overhead should be no closer to the
gauge than twice the height (from the ground) of the receiver funnel.
Temperature Regimes Heat from solar radiation controls the
temperature regimes near the surface of the earth. The temperature at a site is
influenced by incoming solar radiation that, in turn, is modified by secondary
heat transfers from terrestrial radiation and air movements. Temperatures of
either high or low extremes can be detrimental to the establishment and growth
of plants. Hot temperatures, in combination with drying winds, can be damaging
to recently emerged plants, especially under conditions of minimal soil
moisture. Conversely, cold temperatures can delay seed germination and
subsequent early growth, placing the survival of plants in jeopardy. Following
establishment, temperatures of either extremes can reduce the overall growth
performance of most plant species.
For best growth, many plants require nighttime temperatures that
are considerably cooler than daytime temperatures. This difference between
nighttime and daytime temperatures, termed thermoperiod, is important in the
flowering and setting of fruit. In general, plants will become adjusted to
regular diurnal fluctuations in temperatures and, as a result, may not exhibit
"normal behavior" when grown in foreign environments. Therefore, individual
plant species should be selected on the basis of their adaptation to temperature
regimes (including mean, maximum, and minimum temperatures) at a site.
Reliable air temperature data are gathered from simple
thermometers (for instantaneous determinations), maximum-minimum thermometers
(to measure temperature extremes), and thermographs (for a continuous record of
temperatures). Thermometers are generally housed in shelters with louvered sides
to permit air to circulate freely. The shelters should be located at a distance
at least two-thirds the height of any obstructions. Temperature will vary if
obtained on steep slopes or in hollow areas.
The air within plant leaves is usually saturated with moisture
under growing conditions, and vapor therefore will move from the leaves into the
surrounding atmosphere, cooling the atmosphere in the process; this is
transpiration. The rate of transpiration in plants depends in part on the amount
of atmospheric moisture present; the drier the atmosphere, the higher the rate
of water loss. Transpiration is the dominant process in the water balance of
plants and can cause water deficits to occur. Under conditions of limited soil
moisture, these water deficits may be responsible for growth reductions or
To characterize atmospheric moisture at a site in a given period
of time, relative humidity is often measured. With summaries of relative
humidity regimes over a growing season, it may be possible to determine the
changes of transpiration in plants resulting in water deficits. Because certain
plant species are better able to withstand the stresses of water deficits, this
knowledge can be useful in evaluating the value of plant species for
revegetative purposes at a particular site.
Instantaneous measures of relative humidity are obtained from
manual observations of dry- and wet-bulb thermometers on a sling psychrometer.
Hydrographs, of which several types exist, are used to record relative humidity
on a continuous basis. These instruments should be housed in the shelters
Wind The effect of wind on evapotranspiration, the total
moisture loss from soil by evaporation and plants by transpiration, can be
critical, particularly in dry climates. When a plant is exposed to drying winds
and hot temperatures, water deficits in its leaves are likely to occur; this
situation is compounded under minimum soil moisture conditions. The desiccating
impact of wind on plants is demonstrated by low survival rates, stunted growth,
and frequently death in many plant communities of semiarid and arid lands.
Data on wind patterns (prevailing direction, velocities, and
seasonal fluctuations, for example), characterizing a particular site, are
uncommon in many nonindustrialized countries . When this information is
available, it has generally been obtained by using an anemometer during
short-term site visits.
Light Another climatic factor that affects the growth of plants
- an important factor that is seldom measured extensively - is light. Solar
radiation in the visible bands of the spectrum controls photosynthesis. At very
low light intensities, photosynthesis may take place at such a slow rate that
all of the carbon dioxide evolved by respiration is not used; with these
conditions, carbon dioxide is given off by the plant, not absorbed by the plant
from the atmosphere. On the other hand, high light intensities promote rapid
transpiration, which can often have detrimental effects. In general, individual
plant species differ in their relative tolerances to either low or high
intensities of light.
The photoperiodism of plants also differs among species. Some
plants require long photoperiods (that is, length of day) to grow and develop,
while other plants do better with shorter photoperiods. Photoperiods can be
easily measured by the length of daylight at a site.
The word soil refers, in general, to the natural surface layer
of the earth's crust in which plants grow. It is a porous medium, comprising
minerals and organic materials. Living organisms, water, and gases are other
constituents of soil. Whether climate or soil is more important in governing
plant growth is immaterial, since both are necessary.
A site evaluation is normally incomplete without some kind of
soil inventory, classification, or assessment. The evaluation of soil resources
is conducted to determine the capacity of a particular site for a prescribed
range improvement project or program, specifically in terms of supporting
individual plant species or groups of plant species. More general information
may be available from in-country files and experiment stations. Some
international organizations, such as the Food and Agriculture Organization of
the United Nations, can also provide general information (Dudal, 1970).
Evaluations of soil resources are made to provide adequate
information for decision makers. Herein, the decision makers are concerned
principally with the improvement of semiarid and arid rangelands. The kinds of
decisions that these individuals will make must be known before a soil survey
begins. Specific needs will largely determine which soil parameters should be
measured and the procedures to be used in evaluating the soil resources.
It is beyond the scope of this report to describe the many
techniques of conducting a soil evaluation. This information is available in
numerous references; see, for example, Conant et al. (1983), Lutz and Chandler
(1946), and the Soil Resources Inventory Group (1981). Instead, a "checklist"
has been prepared to indicate many of the attributes that may be included in an
evaluation of the soil resources on a site; each item is briefly discussed
below. Obviously, the factors that are ultimately included in a particular soil
survey must be those that relate to decisions made relevant to the particular
range improvement project or program. Emphasis should be placed upon those
factors that are "limiting" to the growth and development of the plant species.
Parent Material The underlying parent material from which soil
develops has an important influence on the type of plants that a site will
support. When the growth of an individual plant species is good on one site but
poor on an adjacent site, investigation will often disclose that the two sites
are characterized by geologic material of differing mineralogical composition
and origin. In general, the soil is derived from the underlying rock. In some
instances, however, the parent material may have been transported to the site by
gravity, water, or wind.
Parent material, a descriptive parameter, is usually determined
by field observations by a competent soil scientist. Geologic maps, if
available, are also helpful in delineating the extent of soil that has been
developed from a parent material.
Depth If soil depth is limited, the development of roots can be
restricted. Soil depth is measured by exposing the soil profile and measuring
the thickness of the separate layers. Many basic soil properties are
characterized by horizon. The number of soil profiles taken at a site depends
largely on the inherent variabilities of the individual properties.
Texture and Structure Two important physical properties of soil
that greatly influence plant growth and development are texture and structure.
Texture refers to the size and distribution of the soil particles (sand, silt,
clay, and mixtures of them in various proportions); structure refers to the
grouping of these particles into aggregates. Texture can affect and may restrict
the development of roots, primarily through its influence on nutrient retention
and aeration. Structure, which is most important in soils high in silt and clay
particles, affects the percolation of water and air. The success of individual
plant species in revegetation is dictated, in many respects, by texture and
structure of the soil at a site.
Both texture and structure are descriptive measures, most
commonly taken by horizon in the soil profile. Care must be exercised to ensure
that samples are representative of the site.
Soil pH Different species of plants generally exhibit a
preference for a degree of acidity or alcalinity in the soil, and have their own
optimum pH values. Because pH may vary from one site to another, it should be
included in a soil survey to maximize the returns from revegetative efforts. The
pH of soil can be determined by using inexpensive but accurate field
Water-Holding Capacity As mentioned above, the survival and
growth of plants is dependent on the availability of water in the soil.
Waterholding capacity is a soil parameter of considerable utility. After
saturated soil has been drained of gravitational water, it is (by definition) at
field capacity. Field capacity is often determined in the laboratory, although
approximations can also be made in the field by using a tensiometer. If desired,
field capacity can be measured by horizon.
Organic Material The accumulation of dead organic material on a
soil surface is significant to the "well-being" of plants in various ways.
Organic material is, in time, a primary source of mineral nutrients. The organic
increment of a soil profile is also a source of food for soil organisms that, in
turn, are the chief causes of decay of the organic material; this process is
critical in the nutrient cycles of a site. Organic material is colloidal, and
thus, its waterholding capacity is relatively high.
Organic material content is minimal on many semiarid and arid
lands. The sparse vegetation and year-round high temperatures favorable for
rapid decomposition do not allow the accumulation of organic matter in
appreciative amounts. The water-holding capacity of these soils is also
frequently low. In general, the presence of organic litter may be quantified
through visual inspection at a site, but differentiation into other compounds
may not be possible except under laboratory conditions.
Salinity Salinity is often a constraint in revegetative
activities. Saline and alkaline soils are commonly found in the valley bottoms
of semiarid and arid lands. These soils create specific difficulties in
selecting appropriate species for planting, and only plant species that are
adapted to these sites should be used. Also, high levels of saline in soil
reduces the amount of water available to plants and, therefore, can accentuate
Soil salinity is frequently measured with the aid of a
Wheatstone bridge (an electrical device which measures conductivity). However,
as is the case in surveying many soil attributes, these measurements are based
on "point samples," which limit their extrapolation because of site variability.
Fertility Individual plant species have their own nutrient
requirements for growth and development. When the soil lacks these nutrients,
certain plant species may not be suitable for revegetation. In that case, it may
be necessary to apply a fertilizer, although this practice may be uneconomical
in an extensive revegetation project or program except for establishment. To the
extent possible, the natural fertility of soil should be ascertained by chemical
analyses. A practical approach to "measuring" soil fertility is to employ native
plants as indicators of fertility ranges. Knowledge of the ecosystem and
successional cycles of a site is necessary for this technique, however.
Quantitative expressions of soil fertility are obtained with soil-testing kits.
Soil Classification The classification of soil is an attempt to
group soils into categories that, in general, are useful in understanding the
dynamics of an ecosystem. It is based, regardless of the system, on an
examination of the "typical" soils in an area. In the process of classification,
a number of soil attributes may be considered, including (but not exclusively)
many of those described above. Soil classification is time-consuming and
generally expensive, but it can provide decision makers with necessary
information for the effective planning of range improvement activities.
Fortunately, many countries have soil survey departments that can furnish
technical assistance for this purpose.
The selection of a soil classification system to be used in a
resource evaluation program is an important consideration. For instance, the
needs of a project with one objective may be met by a specificpurpose,
site-specific soil classification, whereas an integrated rural development
program requires the use of a general purpose soil classification. An example of
the former is an irrigation project aimed at increasing the production of
bananas. In this case, soil properties important to water management
considerations must be used as differentiating criteria in the development of a
specific purpose soil classification. On the other hand, a multifaceted rural
development program requires a general-purpose soil classification to assess the
suitability of soils for a variety of uses. In this case, soil classes must be
defined by attributes relevant to a wide spectrum of management goals.
Several general-purpose soil classification schemes have been
developed by different countries to meet their needs. As Smith (1963) noted, a
soil classification scheme developed in a particular country is biased by the
accidents of geology, climate, and the evolution of life in that country. Its
application in other countries can be problematic.
The FAO/Unesco soil-classification system (Dudal, 1968) and the
U.S Comprehensive Soil Classification System (Soil Survey Staff, 1975) are now
used in many nonindustrialized countries (Conant et al., 1983). The FAO/Unesco
system attempts to group the soils of the world. Because of the wide spectrum of
soil-forming environments, groups in this system include considerable
variability. On the other hand, soil taxonomy was developed to facilitate soil
survey in the United States (Smith, 1963). To avoid ambiguity, soil classes are
precisely delimited by chemical and morphological properties. The rigidity of
class boundaries and the need for laboratory analysis hamper the successful
application of soil taxonomy in nonindustrialized countries. Furthermore, since
the current version of soil taxonomy was based primarily on soils from temperate
regions, its use in tropical areas may be problematic.
In addition to the FAO/Unesco soil grouping and soil taxonomy,
several other soil classification schemes are in use in nonindustrialized
countries. The relationships and main features of several of these are outlined
by Beinroth (1975), Buol et al. (1980), Butler (1980), Camargo and Palmieri
(1979), Conant et al. (1983), Jacomine (1979), and The Soil Survey Staff (1975).
Landform and Relief
Characterizations of landform and relief are necessary to the
evaluation of a site because of their influence on climate and soil conditions.
In many instances, the relation of plant survival to landform and relief is very
close. At a minimum, general landform and relief should be quantified at a macro
In general, an area should be divided into "warm" and "cool"
sites on the basis of aspect and slope combinations. So-called warm sites in the
northern hemisphere are oriented, in a clockwise direction, from southeast to
northwest, while "cool" sites are oriented from northwest to southeast. Of
course, this situation is reversed in the southern hemisphere. Within a
particular aspect class at a given latitude, slope is important when orienting a
site to the sun. More gradual and steeper slopes receive less intensive sunlight
than do "intermediate" slopes; the hottest and often the driest sites are those
that most directly face the sun on a summer day. The amount of solar radiation
received on a site is closely related to other factors (for example,
precipitation, temperature, and soil moisture) that, individually or
collectively, influence the choice of species, establishment, and the growth of
The position of a site on a slope can also determine the growth
potential of an individual plant species. High, convex surfaces, which are
frequently subject to wind erosion and weathering, tend to be drier and (in dry
climates) warmer than is average for an area. Conversely, low, concave surfaces,
on which soil tends to accumulate rather than erode, are generally moister and
cooler than average. Midslopes are typically intermediate in these
Knowledge of the terrain of a site may be helpful in selecting
the most appropriate method of revegetation. For example, level to gently
rolling lands are preferred in many instances because ground preparation, if
necessary, can be more effectively accomplished with machinery at less cost.
Investigation 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 site can be obtained from
topographic maps, if they are available. On site, aspect is normally determined
with a compass, and slope is measured with an Abney hand level (or pocket
altimeter). Aspect and slope can be "integrated" into a single measure of site
orientation through use of daily solar radiation values for explicit
combinations of aspect, slope, and latitude (Buffo et al., 1972; Frank and Lee,
Range improvement projects or programs on semiarid and arid
lands are highly dependent on the distribution and availability of water to me
et 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 groundwater aquifers (for subsequent development) should also be
studied. In general, estimates of potential yields and (as mentioned below)
quality of water resources may be necessary 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 "tolerance" 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 assessing 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).
Plants, animals, and humans comprise the biotic components of a
site. The importance of these components and ways of measuring them are
The native plants that are growing on a site, if any, can be
helpful in describing the inherent productivity of the site and, from this
knowledge, the chances for a successful range improvement activity. The
occurrence of key" plants can often be used to indicate site quality.
Also, knowledge of the productivity levels of native plants can index"
levels of production that might be expected from subsequent range improvement
activities. Observations of plants that can be important in the evaluation of a
site include, but are not limited to, identification of the individual plant
species (taxonomy), properties of the individual plant species (for example,
chemical composition and particularly, the traditional uses of the plants which
indicate important properties), groupings of the individual plant species into
communities, and vegetation-soil-terrain relations.
Of course, interpretations of individual plants and communities
of plants must be undertaken in light of the on-site land-use patterns. Use of
plant resources as described above can be hampered by land management practices
that result in excessive utilization of the plants on a site. Because previous
and current land uses may tend to cloud the picture, the ecological impacts of
these previous or existing land use patterns on the plant resources must be well
known and thoroughly understood.
Plant Indicators Various key plants may be useful in analyzing
the capacity of a site for range improvement. To a large extent, the presence,
abundance, and size of these plants will often reflect the nature of the
ecosystem of which they are a part and, therefore, may serve as indicators of
site quality. However, the correlations between key" plants and associated
site quality, which are generally based on detailed ecological investigation,
may not always be apparent. Effects of competition among individual plant
species, events in the history of plant development (such as drought, fire, and
outbreaks of insects), and land management practices can weaken a plant
association to the point that it has little predictive value. Nevertheless, in
many situations, site quality is sufficiently reflected by plant indicators to
make use of the latter in an evaluation of a site for range improvement.
Sometimes, the occurrence of plant indicators is combined with
abiotic components of the environment (for example, climate, soil, and
topography ) in an attempt to describe more accurately the quality of a site.
The more factors that are taken into consideration, the better is the estimate
of site quality and, consequently, the understanding of the potential of a site
for improvement practices. Comprehensive reviews and comparisons of site
evaluation, including its history, methods, and applications, have been prepared
by Jones (1969) and Carmean (1975).
Productivity Levels Knowledge of the productivity levels (that
is, amounts of plant material present) of plants growing on a site can provide
insight into what might be expected from any range improvement practice.
Information regarding the total production of all herbaceous plants, taking into
account the loss of plant material to utilization, is often used as a
"threshold" productivity value. In other words, improvement should be expected
to exceed the existing productivity levels. If excessive utilization of the
plants has occurred, the measures of existing production may be biased downward.
Volumetric measurements of plants are seldom made to quantify
productivity levels. Instead, weights are used to measure the biomass of the
plant material present. The weights of plants are most precisely obtained by the
clipping of sample plots. But, since clipping is time-consuming and costly, a
double sampling procedure is frequently employed to measure productivity on an
extensive basis; weights of plants are estimated on all plots, with only a few
plots clipped to derive a factor to correct the estimates, if necessary.
Whenever feasible, productivity levels should be obtained on the
basis of individual plant species to allow subsequent groupings into plantform
categories or grazing value classes for decision-making purposes.
Plant Cover In addition to the productivity or biomass available
for utilization, the ability of the plant community to stabilize the site and
arrest the soil erosion process should also be determined. Productivity
information alone does not provide the manager with this knowledge. The
percentage of the soil surface that is covered by plants, either only by the
base of the plant (basal cover) or by all above-ground plant parts when viewed
from above the canopy (canopy cover), indicates both the susceptibility of the
site to erosion and the established dominance of one plant species over another.
Plant Number A plant community might be dominated, in terms of
productivity and cover, by one or two plant species, the individuals of which
are old and decadent. As these individuals die, they will be replaced by the
same or new species. Data on number of plants of each species may give the land
manager an indication of the health (vigor) and reproductive status of species
in the community and, therefore, insight as to which species are likely to
increase or decrease. Knowledge of this sort will guide the selection of the
appropriate range improvement practice.
For more detailed information concerning techniques for
vegetation analyses, the reader is referred to Conant et al. (1983), a
publication prepared specifically for efforts in nonindustrialized countries.
Other Measurements and Observations To help in the selection of
individual plant species for revegetation projects and programs, there may well
be other kinds of on-site surveys or observations of plant resources that should
be taken. Depending on the goals of the improvement practice, these may include
growth forms and plant community structures (that is, vertical layerings);
seasonal growth, development, and maturity patterns, including the differences
among grasses and forbs, shrubs, and trees; and ecological conditions and trends
(Pratt and Gwynne, 1977), as these parameters are influenced by successional
cycles and degree of site deterioration.
Individually and collectively, animals have a major impact on
the physical environments and the plant communities with which they are
associated, and, as a result, can affect range improvement activities in diverse
ways. Depending on the activity, these impacts can be beneficial, detrimental,
or both. Some animals greatly influence the ecosystem processes that are basic
requirements for plant growth and development, such as nutrient and water
cycling. Successional patterns are affected by other animals, by regulating
competition, development, and productivity among individual plant species and
communities of plants.
A major influence on the success of range improvement activities
is the grazing activity of larger ruminant herbivores. However, both the
positive and the negative roles that animals play in an ecosystem should be
considered in a site evaluation.
Many semiarid and arid lands furnish habitats for wild animals
and domestic livestock. Therefore, knowledge of animal types that occur on a
site, their distribution and routes of migration, and their ownership or legal
status can dictate, to some degree, the options for range improvement.
Animal Types All types of avian and terrestrial fauna (including
soil biota) are part of an ecosystem. Difficulties arise, however, in defining
the geographic boundaries when more-mobile animals are evaluated. In practice,
ecosystems are commonly based on plant communities, soil classification units,
or other abiotic features, or combinations thereof, and animals are then
incorporated into the delineated ecosystems as consumers and
secondary users. Mobile animals generally roam over several ecosystems.
Wild animals have varying effects on the ecosystem. Earthworms,
arthropods, and ground-dwelling mammals play major roles in the decomposition of
organic material. In their absence, the nutrient cycles of a site can be
adversely disrupted. Birds are important agents of seed dispersal for many
individual plant species. This dispersal activity can be beneficial or harmful
to reproductive strategies. Mammals, especially rodents, can also be important
agents of seed dispersal in many plant communities.
The grazing activities of the larger ruminant herbivores, both
wild species and domestic livestock, have already been mentioned, and are
covered in more detail in chapter 6. Grazing is commonly considered destructive,
although it can benefit the desired vegetation on a site by removing competitive
plants that otherwise may use limiting water and nutrient resources. Grazing
activities also prevent the buildup of coarse, unpalatable plant parts and
stimulate the growth and tillering of more plant materials.
Techniques of enumerating animal types and their respective
numbers, including the censusing or sampling of animal populations, are
described in Child et al. (1984), Conant et al. (1983), and Schemnitz (1980).
Distribution and Migration Patterns In addition to knowing what
types of animals occur, knowledge of their distribution and patterns of
migration can also be important in site evaluation. Uniformly distributed animal
populations generally tend to exert uniform effects on a site. On the other
hand, a population of animals that is unevenly distributed will frequently have
uneven effects upon a site (for example, animals clustered around a wellhead).
The distribution of animals is also influenced by their migratory patterns. In
general, migration (whether seasonal, yearly, or indeterminate in response to
unknown stimuli) can result in cycles of impacts that should be known when
planning a range improvement program.
Information regarding the distribution of animals can often be
obtained while their kind and number are being enumerated. Migratory patterns,
which are descriptive measures, can be determined only through repeated
observations of the animals on a site.
Ownership Status The ownership of animals can be important to a
range improvement activity, particularly in situations in which the control of
the animals is necessary to the success of the venture. In general, the
ownership of wild animals, if specified by law, lies with the state, which may
assume responsibility for their regulation. However, domestic livestock are
often privately owned by individuals or groups of individuals that operate in a
cooperative. The ownership of animals must be established, and the responsible
parties contacted and their cooperation obtained, if manipulation of the animal
populations is considered necessary to ensure the success of an improvement
project or program.
It is necessary to assemble and analyze what is known about the
human users of the land and, of equal importance, what values people attach to
the natural resources that will be affected by a range improvement activity.
Deficiencies of information in this area can, and in most cases do, constrain
the effectiveness of a project or program. Serious conflicts often exist between
traditional land management practices and what might be proposed in a range
improvement plan. Therefore, it is imperative that proponents of range
improvement understand the people who will be affected, and the reasons why the
people do what they do (see National Research Council, 1986).
Information regarding human activities, land use in the area of
concern, population densities and community structures, and the migration of
families and family groups is a minimum baseline for the evaluation of humans.
Rural sociologists, ethnologists, cultural geographers, and ethnic botanists,
all working at the local level, should be involved in this