STEVE WHISENANT, Department of Rangeland Ecology and Management, Texas A&M University, College Station, TX 77843-2126.
Abstract. Since no brush sculpting technique is appropriate for all situations, we must develop the most effective method for each unique situation. That requires an appraisal of resource potential; clearly stated goals for brush composition, size, and density; and a practical assessment of potential treatment alternatives. Our choice of specific brush sculpting methods is influenced by: (1) practical considerations; (2) regulatory restrictions; (3) degree of selectivity needed; (4) the density, age and size of brush; (5) resprouting ability; (6) potential for creating new problems; and (7) maintenance requirements. In general, brush sculpting methods that treat individual plants are more practical in areas with lower plant densities. Broadcast-applied methods, such as burning, certain mechanical methods and aerial spraying, are often restricted by reduced selectivity. Since greater brush changes require more effort (time, money & labor), brush sculpting activities that occur during the preventive maintenance or early intervention stages are most effective.
When developing our brush sculpting plan, we should consider three general topics. What do I have now? What are my brush sculpting goals? How do I achieve those goals? We usually begin with a general concept of our land use goals, which often includes a desire for more quail, whitetail deer, songbirds, or recreation-related income. Or we may simply want to increase livestock production or alter the visual appearance of the area. More commonly, we want to achieve some unique combination of several objectives. Brush sculpting implies an appreciation for both the benefits and problems associated with each species of brush. Since other papers in this symposium address the requirements for specific land uses, I’ll briefly discuss several questions that should be considered when developing brush sculpting strategies. Then subsequent papers will provide more in-depth discussions of specific brush sculpting methods.
What do I have now?
Effective brush sculpting programs have specific goals for brush composition, size, and density. Only after appraising the existing vegetation can we set clear and achievable brush sculpting goals. After determining the current composition, size, and density of brush, we should consider its potential contribution toward our general land-use goals. Which components of the existing brush community are contributing to our land-use objectives and which are not? Are desirable species present in appropriate amounts (density, cover, production)? Do other species reduce our ability to achieve land-use goals because they are undesirable, too dense, or inhibit more desirable species? Are important species missing or less common than desired?
What are my brush sculpting goals?
Our management objectives, or the relative importance of several objectives, are determined by land-use goals, social interactions, economics, management preferences, and the constraints imposed by the biotic and abiotic environment. As a result, brush sculpting programs driven by livestock production economics will differ from those that emphasize wildlife habitat improvement. Our own sense of esthetics will also influence brush sculpting objectives.
Whatever our management objectives, we must decide what brush mixture would most effectively achieve those objectives. That requires site specific brush goals. Thus, land-use goals such as “improve wildlife habitat” must be restated as specific brush sculpting goals such as “reduce juniper cover to less than 5% and mesquite cover to less than 10% without damaging existing redbud, ephedra, and elbowbush plants” and “only the largest juniper and mesquite trees should remain untreated”. Site- specific brush sculpting goals that address species composition, size and density increase the likelihood that an effective brush sculpting strategy will be developed.
Although brush sculpting goals should be established for each site, practical restrictions, i.e., like money and time, require that we set priorities among those sites. Although many factors influence site selection decisions, we should at least consider beginning where it will do the most good. For livestock production that might include reducing pricklypear or juniper coverage on the best soils, or clearing a calving or lambing pasture to make it easier to view the animals. For quail we might develop loafing cover on sandy soils. Whitetail deer management may benefit most from selective brush sculpting that increases the diversity of forbs and quality browse while reducing unused brush and maintaining screening cover. Whatever your goals and priorities, decide what is most important and develop a long-term plan that addresses those priorities.
How do I achieve my brush sculpting goals?
Brush sculpting provides an avenue for reaching our goals by taking advantage of selective strategies for removing (or reducing) certain species while encouraging or even adding others. The next several papers in this symposium describe the strengths and weaknesses of specific brush sculpting tools (mechanical, chemical, fire, and biological). Charles Coffman will discuss methods for propagating and reestablishing various brush species and Dale Rollins will discuss the importance of landscape configuration. Although several technologies are available for brush sculpting, none are appropriate for all situations. Properly selected, sequenced, and applied brush sculpting strategies reduce treatment costs and maximize long-term benefits. Without understanding the unique strengths and characteristic weaknesses of potential treatment methods it will be difficult to achieve brush sculpting goals.
Our selection of specific brush sculpting technologies should be influenced by: (1) practical considerations; (2) regulatory restrictions; (3) degree of selectivity needed; (4) the density, age and size of brush; (5) resprouting ability; (6) potential for creating new problems; and (7) maintenance requirements. In general, brush sculpting technologies that treat individual plants are restricted to areas with low plant densities, although, that may be less restrictive than previously believed–at least with some herbicide treatments. Broadcast techniques–burning, certain mechanical methods, aerial spraying–may have limited selectivity. Those methods may not effectively control target species without damaging desired species. However, there are important exceptions to these general patterns and several other papers in this symposium will provide examples.
Practical considerations. The availability of the necessary equipment, treatment costs, and labor requirements restrict some treatment options while favoring others. Implementation difficulties associated with a particular property will limit other options. For example, the use of fire may be restricted by a shortage of fuel, difficulties in preparing adequate firelines, or a lack of training. I’m often asked by ranchers if they have enough grass to burn. The real issue is whether there is enough fuel to accomplish your brush sculpting objectives. Although there may be enough fuel to burn, there may be insufficient fuel to significantly affect the target plants.
Regulatory restrictions. Herbicides should always be applied according to label instructions, which may vary for each species, herbicide, and even between counties. Local regulations may restrict herbicide use because of the potential presence of endangered species or application cutoff dates. The Texas Air Quality Control Board places several restrictions on rangeland burning. The fire must carry smoke and other pollutants away from any city, town, residential, recreational, commercial, or industrial area, navigable water, public road, or landing strip. It should be conducted in a manner to prevent a shift in wind direction from producing adverse effects to persons, animals, or property during the burning period. They require fires be started after 9 am and completed as soon as is reasonably practical prior to 5 p.m. They also require that fires occur when winds are between 6 and 23 miles per hour. No fire should be started during actual or predicted persistent low-level atmospheric temperature inversions. There are additional restrictions in heavily populated coastal counties with dense cordgrass stands.
Degree of selectivity needed. The importance and pursuit of selectivity are distinguishing features of brush sculpturing programs compared to previous approaches. This addition and/or subtraction of individual plants or species provides a powerful habitat management tool that deserves far more emphasis in the future. Fundamental planning considerations include: (1) what degree of selectivity is desired; and (2) what methods provide that selectivity.
Fire is used as a broadcast treatment that affects all plants to some degree. However, that impact varies with species, season, age, and size of the plant in addition to the intensity and frequency of burning. Skilled practitioners of fire can achieve a remarkable degree of selectivity, but there are still many limitations. Fire is most effective when used to reduce undesirable brush during the preventive maintenance and early intervention stages (Fig. 1).
The major strengths of the new individual plant herbicidal methods are the relatively minor equipment investment, high degree of selectivity, and flexible timing of labor requirements. Broadcast herbicide applications are restricted by adjacent cropland with susceptible crops and by the presence of desirable brush species that may also be susceptible. Fortunately, there are several selective broadcast uses of herbicides for Texas rangelands. It is just as important to understand what species are tolerant of each herbicide as it is to know which species are susceptible to that herbicide. This knowledge provides the basis for developing selective, broadcast applications. Broadcast applications of less selective herbicides may even be applied in specific patterns (strips, grids, along topographic boundaries, etc.) to provide a lesser degree of brush sculpting. Individual plant treatments with hand-applied herbicides or mechanical methods provide the ultimate in selectivity. This allows you to select the species, size, and even location of brush to be killed, planted, or left untreated.
Density, size and age of brush. Treating (or planting) individual plants provides an opportunity for maximum selectivity. However, the practical value of individual plant treatments is restricted by the density and size of plants to be removed (or planted). With individual plant treatments, costs escalate rapidly as the density and size of treated brush increases. Larger trees might be more efficiently treated with selective mechanical methods. Although, broadcast treatments like aerial spraying and prescribed fire are not automatically more expensive on denser, older stands–they may be less effective. Broadcast mechanical methods (such as chaining, roller chopping and rootplowing) may become somewhat more expensive where larger more dense brush are present, but the differential is less than with individual plant treatments. The old adage “an ounce of prevention is worth a pound of cure” is never more appropriate than when planning any brush sculpting program (Fig. 1). It will be far easier and more effective to maintain existing areas than it will be to create major changes in the brush composition.
Resprouting ability. The ability of many brush species to resprout from the base when the top is killed or removed may be either a problem or an opportunity. It is a problem when we are unable to kill mesquite, redberry juniper, huisache, and others with fire, some herbicides, or mechanical methods that only remove the top. It creates opportunities when we use the same methods to reduce the height of desirable browse plants, thus making the browse more readily available to wild or domestic animals.
Potential for creating new problems. Always consider the possibility that a potential brush sculpting method will create additional problems. The most common problems arise following chaining or roller chopping areas with prickly pear. Any mechanical treatment that scatters pricklypear pads or pieces of pads can potentially cause problems. Without follow-up pricklypear treatments, these sites often become dominated by pricklypear. Continued mechanical or non-lethal chemical treatment of strong resprouters–like mesquite–may increase stem density enough to cause greater problems than the original untreated situation.
Maintenance. Effective brush sculpting is not a one-shot affair. We should start thinking about maintaining brush sculptured areas when planning the original treatments. Initial treatments may be relatively expensive, so there is ample incentive for extending the length of treatment effectiveness. One way to extend treatment life is to periodically apply low-cost secondary treatments to maintain original treatment effectiveness. When possible, it will be most effective to use grazing animals and/or prescribed fire to maintain and extend treatment life.
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Updated: Mar. 18, 1997