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Management and Use of Browse in the
Edwards Plateau of Texas
Stephan A. Nelle
range from harmless to highly desirable from a ranching
point of view.
Ungulates which rely upon browse for a significant part of
their diet are the primary rangeland consumers of the
region. Texas has more goats, sheep, deer and exotic wild
ungulates than any other state. The majority of these animals within Texas are produced in the Edwards Plateau.
With the combined population at about four million (Findley
1994; Traweek 1989; Karns 1993), the average density of
these animals in the region is one per six acres. On many
ranches their density equals or exceeds one per three acres.
This region has the heaviest concentration of shrub-eating
animals in the United States.
Abstract-Range management in Texas has enjoyed a long and
rich past with many noteworthy accomplishments. These efforts
have been aimed primarily at improved management of grasslands
and control of noxious woody plants. Desirable forage-producing
woody plants are an unrecognized resource, and the management of
shrublands as a valuable resource is a heretical concept to many
range professionals. The lack of concern for and management of this
resource has caused the higher quality forage plants to decline or
disappear from many ranges and the lower quality forage plants to
proliferate to problem levels. Basic range management principles
adapted to woody plants can be used to help restore deteriorated
shrub lands and manage them as a renewable and sustainable
resource.
Principles of Browse
Management
The Edwards Plateau is one ofthe ten ecological regions of
Texas. The 24 million acre region lies in the central and
southwestern portion of the state and is dominated by
shallow, rocky soils over fractured limestone. Average annual rainfall ranges from 12 inches in the west to 32 inches
in the east. The region is mostly privately owned native
rangeland. The rural agricultural economy is based on
livestock ranching and lease hunting for white-tailed deer.
Ecologists are divided about the historic extent of trees
and shrubs in the region prior to European settlement
(Weniger 1984). Historical accounts can be found to support
the notion that the region was a grassland with only scattered areas of woody vegetation. Other accounts are used to
contend that the area was a shrubland-woodland with a
herbaceous understory and scattered open prairies. Regardless of the composition of the historic landscape, the region
has been dominated by woody plants for at least the past 50
years. Annual production ofleaves and twigs of woody plants
is commonly in the range of 500 to 2000 pounds per acre and
often exceeds the production of grass and forbs.
Of the 200 native species oftrees, shrubs and woody vines
in the region, about 60 are common and comprise the bulk of
the browse resource. The traditional simplistic view ofland
management in the region is that woody species have invaded productive grasslands and need to be controlled. A
more realistic viewpoint is that all woody plants cannot be
lumped together under the category of "noxious brush."
Only about 10 species are invasive plants which cause
problems and for which control may be justified. The others
Despite the abundance of browse plants and browsing
animals, little or no research has been conducted in the
region which can be used as a basis for management. The
management principles outlined here are based on observation, experience, studies from other regions, and the application of basic range ecology principles to browse.
Selectivity
Animals selectively browse some plant species in preference to others. Over a period of years, this uncontrolled
selectivity will eliminate the best browse plants and favor
the increase of less desirable browse plants .. This is one
important reason why some woody species such as junipers
have developed into major brush problems, while other
species have almost disappeared. This order of selection is
somewhat predictable and enables managers to group woody
plants into four categories of preference (table 1).
Class I plants are highly preferred. They often show heavy
use and poor reproduction even with only moderate numbers
of browsing animals. Although Class I plants are very
nutritious and palatable, they are normally so scarce that
they do not contribute significantly to animal diets.
Class II plants are moderately preferred. Under proper
management, this class of plants can contribute significantly to animal diets. On ranches with excessive numbers
ofgoats and/or deer, these plants will be heavily used, in poor
vigor, and will not be successfully reproducing.
Class III plants are not preferred in relation to Class I and
II plants. They are abundant on many ranches and often
make up the bulk ofthe browse diet. The nutritional quality
provided by these plants is frequently below optimum for
browsing animals.
Class IV plants are aversive to browsing animals. They
are the last to be used and will only be consumed in quantity
I~: Barrow, Jerry R.; McArthur, E. Durant; Sosebee, Ronald E.; Tausch,
Robm J., comps. 1996. Proceedings: shrubland ecosystem dynamics in a
changing environment; 1995 May 23-25; Las Cruces, NM. Gen. Tech. Rep.
INT-GTR-338. Ogden, UT: U.S. Department of Agriculture, Forest Service
Intermountain Research Station.
'
Stephan A. Nelle is Biologist, Natural Resources Conservation Service 33
East Twohig, Room 108, San Angelo, TX 76903.
'
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when little else is available. When these plants show significant use, it is a sign of severe browse deterioration. These are
the species that often become brush problems. Since they are
not readily consumed, they have a competitive advantage
and often reproduce with abundance.
One important principle to apply to the concept of preference and selectivity is that availability dictates consumption. If there are no Class I or II plants available, then Class
III plants become the most preferred class by default. Exceptions to the general order of preference do occur, especially
seasonally. Preference also occurs within each class although much less predictably.
Table 1-Common woody plants of the Edwards Plateau by
class.
Class I
Kidneywood (Eysenhardtia texana)
Littleleaf leadtree (Leucaena retusa)
Texas sophora (Sophora affinis)
Carolina buckthorn (Rhamnus caroliniana)
Mountain mahogany (Cercocarpus montanus)
Texas mulberry (Morus microphylla)
White honeysuckle (Lonicera albiflora)
Texas oak (Quercus texana)
Black cherry (Prunus serotina)
Hawthorne (Crataegus crusgalll)
Rusty blackhaw (Viburnum rufidulum)
Inland ceanothus (Ceanothus herbacea)
Class II
Hackberry (Celtis reticulata)
Cedar elm (Ulmus crassifolia)
Bumelia (Bumelia languinosa)
Clematis (Clematis drummondil)
Roemer acacia (Acacia roemeriana)
Redbud (Cercis canadensis)
Grapevine (Vitis sp.)
Virginia creeper (Parthenocissus quinquefolia)
Greenbriar (Smilax bona~nox)
Carolina snailseed (Cocculus carolinus)
Poison ivy (Rhus toxicodendron)
Western soapberry (Sapindus drummondit)
Elbowbush (Forestiera pubescens)
Netleaf forestiera (Forestiera reticulata)
Ephedra (Ephedra antisyphyllitica)
Class III
Live oak (Quercus virginiana)
White shin oak (Quercus durandit)
Vasey shin oak (Quercus pungens)
Skunkbush sumac (Rhus trilobata)
Evergreen sumac (Rhus virens)
Flameleaf sumac (Rhus copallina)
Littleleaf sumac (Rhus microphylla)
Hogplum (Colubrina texensis)
Feather dalea (Dalea formosa)
Catclaw acacia (Acacia greggil)
Peachbrush (Prunus minutiflora)
Fourwing saltbush (Atriplex canescens)
Class IV
Blueberry cedar (Juniperus ashel)
Redberry cedar (Juniperus pinchotil)
Mesquite (Prosopis glandulosa)
Mountain laurel (Sophora secundiflora)
Catclaw mimosa (Mimosa biuncifera)
Lotebush (Zizyphus obtusifolia)
Condalia (Condalia sp.)
Javelinabush (Microrhamnus ericoides)
Agarita (Berberis trifoliata)
Texas persimmon (Diospyros texana)
Whitebrush (Alloysia Iycoides)
Wolfberry (Lycium berlandiert)
Pricklyash (Xanthoxylem clava-hercules)
Mexican buckeye (Ungnadia speciosa)
Degree of Use
Woody plants, like all other plants, respond to different
levels of utilization or leaf removal. Browse plants remain
healthy and productive when they are browsed moderately.
The old range management principle "Take Half and Leave
Half' is a good rule of thumb for browse. This ensures
adequate photosynthetic leaf surface to convert sunlight to
plant energy. At this moderate level of use, browse plants are
a totally renewable and sustainable forage resource.
When browse plants are heavily used for prolonged periods, they will loose vigor, decline in productivity, and cease
to successfully reproduce. With insufficient leaf surface to
maintain itself, weakened plants are more vulnerable to
drought and other stresses and will die prematurely.
Use of browse is expressed as the percentage of current
years growth of available leaves and twigs removed by
browsing animals. Browse use is divided into three
categories:
0 - 40%
Light use
Moderate use 40 - 65%
Heavy use
65 - 100%
Light use does not allow for the most efficient use of the
forge resource since much browse goes unused. Light use of
Class I, II, or III plants is seldom seen on ranches with
moderate numbers of goats or deer. Light use is recommended to allow formerly heavily used browse to recover, to
maximize woody cover for wildlife, or to provide maximum
selectivity and maximize animal nutrition.
Moderate use should be the management goal for sustained browse production and is compatible with good livestock production, good wildlife production and good ecosystem health.
Heavy use of browse will result in loss of vigor and
production and will suppress reproduction. Heavy use is not
compatible with good livestock or wildlife production or with
ecosystem health.
Degree of use will vary within a pasture between plant
species. With moderate use on Class III plants, most Class
II plants will be heavily used and most Class IV plants
lightly used. The manger must decide which group of plants
he wishes to base management on.
Rest Periods
Periodic rest from livestock browsing is important for
proper browse management. Rest periods allow the most
preferred plants a time for recovery between browsing periods. This also allows flowering, seed maturation, and a
better chance for seedling establishment than continuous
browsing. Rest periods are best provided by some kind of
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planned grazing system where a herd oflivestock is rotated
among two or more pastures.
The key to the success of a grazing system for browse is the
frequency and length of rest periods. Rest should be provided
at least once every one or two years. The length ofrest should
be four to six months. Since browse grows and responds
slower than grass, rest periods must be longer than used for
grass dominated grazing systems.
Even when goats or sheep are moved out of a pasture for
a rest period, deer continue to browse and are in fact
attracted to a rested pasture. So, rest periods are actually
only a time of reduced browsing, not a complete rest. Where
deer numbers are very high, rest from livestock browsing
may not accomplish the desired results. Deer numbers must
then be significantly reduced to allow proper management of
the browse resource.
Figure 1-The natural growth form of live oak and
most other woody species in the region.
Reading Browse Signs _ _ _ __
The current condition of the browse resource is the result
of how it was managed in the past. An accurate history of the
management of shrublands can be determined by learning
how to read several key browse signs. Managers must be
able to recognize these signs of past use in order to assess the
condition ofthe resource and determine needed management.
Hedging
Hedging is the growth form of woody plants that develops
over a period of years when terminal twigs are browsed
causing lateral twigs to develop. As the lateral twigs are
browsed, a compound, multi-branched twig arrangement
develops.
Moderate hedging is not harmful to a plant if adequate leaf
surface is retained. Moderate hedging keeps more of the
production within reach of animals.
Severe hedging creates a network of short stubby branches
with limited leaf production. Severe hedging signifies poor
plant vigor and greatly decreased browse production. Severely hedged shrubs often have dead or dying twigs and
branches, limited flowering and fruiting, and greatly reduced leaf size.
Figure 2-Prolonged heavy use has greatly reduced
the vigor and production of lower branches of live oak.
Browse Lines
The natural growth form of most woody species in the
region is shrubby with branches, twigs and leaves near
ground level as well as in the upper canopy (fig. 1). Browse
lines develop on taller shrubs and trees subjected to heavy
browsing by the removal of branch , twig and leafproduction
within reach of animals (fig. 2). The progressive pruning and
reduction of low-growing branches is how browse lines
begin. As they worsen, lower branches die and are broken off.
Distinct browse lines signify long-term heavy use of the
species and little or no production within reach of animals
(fig. 3). The height of a browse line varies with the animal.
White-tailed deer normally browse to only a three or four foot
height. Goats can browse up to four or five feet in a bipedal
position. Certain large exotics can browse to a six foot height
or more.
Figure 3-Pronounced browse lines signify longterm heavy use of live oak with little or no available
production.
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Unlike severe hedging where the entire plant is threatened, browse lines only affect the lower part ofthe plant. The
upper canopy and the shrub itself will remain healthy since
much of it is above browsing height. Although the plant
remains healthy, it is not producing browse which is available to animals. Furthermore, seedling recruitment is limited even though the plant may be producing abundant seed.
Reproduction
Adequate reproduction does not occur on heavily browsed
species. A lack of seedlings and young plants signifies that
the species may not be perpetuating itself and is therefore in
decline even though there may be an abundance of mature
plants. Fortunately, many species in the region are root
sprouters, and vegetative reproduction is possible even if
sexual reproduction is not. Excessive reproduction of Class
IV plants and inadequate reproduction of Class I and II
plants is the rule over most of the region.
Figure 4-Deteriorated browse will recover with proper
rest periods and moderate use. Root sprouts of live oak
will fill the void below past browse lines.
Animal Condition
production is mostly a matter of changing its growth form to
make it more accessible to animals. Physical damage to the
top growth of most species will cause prolific basal or root
sprouting. This damage can be caused mechanically (chaining, roller chopping, dozing or firewood harvest) or with fire
(fig. 5). These practices often increase the availability of
browse five to ten fold.
Another excellent way to increase browse production is to
selectively remove competing Class IV brush species which
can dominate a site to the detriment of better species.
Selective dozing, individual plant treatment with herbicides
or hand cutting of non-sprouting blueberry cedar are all used
to control brush species and release better browse species.
Periodic prescribed fire is needed to control cedar seedlings
before they get too big and to keep sprouting species such as
oaks within browsing height.
The physical condition of animals is another sign that can
be used to assess browse condition. Since deer rely on browse
more than any other animal and are seldom maintained
with supplemental feed, deer performance is a good secondary indicator for managers. Average fall fawn crops below
50%, field dressed weights of mature does below 60 pounds,
mature bucks below 100 pounds, and an abundance ofspikes
indicate poor nutrition and poor browse condition.
Putting Principles into
Practice
The principles ofbrowse management although not highly
scientific nor proven by research can be used to improve
shrubland ecosystems both ecologically and economically for
both ranchers and society.
Recovery of Deteriorated Browse
When signs of past heavy browse use are evident, especially on Class III and IV species, and the manager desires
improvement, drastic measures must be taken and a long
term commitment made. If browse has been heavily used
for many years, a long initial rest of one to three years from
all goat grazing and a drastic reduction in deer numbers may
be needed. Browse lines will begin to fill in with growth from
basal sprouts or root sprouts (fig. 4). Following the extended
rest, proper stocking rates to achieve moderate use must be
established and a grazing system initiated to provide needed
rest periods. In general goats should not make up more than
50% of the stocking rate.
Stimulating Browse Production
Figure 5-Browse stimulation can be accomplished
by firewood harvest or prescribed burning, which
converts taller trees to shorter shrubs.
On ranges where the basic resource is stable and the
manager desires to stimulate increased browse production,
several options exist. The basis behind stimulating browse
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Biological Control of Shrubs
long-term sustainability. Ranching can remain profitable
and ecologically sound when both the grass and shrub
communities are properly managed. Both grazing and browsing animals belong in the region in proper numbers balanced
to the forage resource. Woody plants, long considered a
problem in need of control can also be considered an asset in
need of wise management.
The intentional use of goats to control or suppress woody
plants has been widely employed. Because of the notion that
invasive shrubs destroy grasslands, the use of shrub eating
animals is appealing to those who want to convert shrublands
to grasslands. Goats are called by some "environmentally
friendly" or "natures herbicide" with the perception that
they control undesirable brush, help restore grasslands and
reduce the use of herbicides. Heavy stocking rates of goats
will control or suppress Class I, II and III plants very
effectively. Control of Class IV brush species is much less
effective and is difficult to achieve without abuse to the
entire vegetative resource.
Conclusions
References
--------------------------------
Findley, Dennis S. 1994. 1993 Texas livestock statistics; Bull.
252(1). Texas Agricultural Statistics Service. 52 p.
Karns, Patrick D. 1993. White-tailed deer population trends. Texas
Parks and Wildlife Department Fed. Aid Proj. No. W-127-R-2.
60 p.
Traweek, Max S. 1989. Statewide census of exotic big game animals.
Texas Parks and Wildlife Department Fed. Aid Proj. No. W-109R-12. 52 p.
Weniger, Del. 1984. The explorers' Texas the lands and waters.
Austin, TX.: Eakin Press. 224 p.
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The Edwards Plateau is a region with a rich diversity of
mostly desirable woody plants which can be managed for
155