Range condition as related to desertification and livestock production

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Range condition and sites as related to grazing capacity and animal production

Range condition is a very important concept and measurement. Consequently, there are various opinions as to what it entails and how it should be measured. The Society for Range Management (SRM) gives two definitions in its Third Edition of "A Glossary of Terms Used in Range Management" (SRM, 1989). These are: (1) a generic term relating to present status of a unit of range in terms of specific values or potentials which must be stated; and (2) following some agencies, the present state of vegetation of a range site in relation to the climax (natural potential) plant community for that site. It is an expression of the relative degree to whiah the kinds, proportions, and amounts of plants in a community resemble that of the climax community for the site.

Fundamentally, range condition is a measure of the deviation from the highest form of vegetation that can be attained with proper and practical management. The key is proper management that leads to maximum sustained livestock production consistent with the conservation and/or improvement of the related natural resources. Agencies in the U.S. have developed guides for determining range condition based on the decreases, increaser and invader classifications. Range condition classes using this method are given in Table 5 and illustrated in Figures 11 and 12.

Table 5. Range condition classification based on percent of climax (natural potential) present for the site

Since the ecology of the individual species is not well known in most of the Region's countries, Huss, et al. (1986) developed a modified method for range condition classification based on the desirable species concept. The guidelines for determining condition are as follows:

Desirable Species:
Allow the total percent of all that occur towards range condition classification.

Less Desirable Species:
Allow a total of up to 30%, but no more, of these towards range condition classification.

Undesirable Species:
Do not allow any of these.

The range condition classes using this method are shown in Table 6.

Table 6. Range condition classification based on the proportions of desirable, less desirable and undesirable species. (Adapted from Huss, et al., 1986)

The general characteristics of the four range condition classes are illustrated in Figure 13. Excellent condition is dominated by highly productive, palatable and deep rooted desirable species. There are a few less desirable ones. Grazing capacity is maximum. The ground is well covered and the soil is filled with desirable roots. The environment is stable and there is no desertification.

Good condition has a reduction of desirable and more less desirable species than excellent. Grazing capacity is slightly less, but satisfactory. Ground cover and root supply are sufficient to stabilize the environment. Everything begins to fall apart with fair condition. Undesirable and high water-using species have invaded, upsetting the water regime. There are only a few desirable species. Grazing capacity is greatly reduced. Ground cover and root production are reduced, creating excessive runoff and erosion hazards. The microclimate has become more arid and desertification symptoms are everywhere.

The situation becomes worse with poor condition, although a desertified state has not been reached in this example. Note that a few desirable and less desirable plants still exist within the cactus plants because they are protected from grazing. A range in this state can be improved via secondary succession with good management. However, with continued destructive grazing, the poor range will become even worse, finally reaching an irreversible state.

Range Sites and Condition

The different kinds of rangelands are large areas controlled by climate and distinguished by the dominance of certain kinds of plants. They are not homogeneous. Upon close inspection, one can find considerable variation in plant communities and productivities. These variations are due to range sites. A range site is an area of land having a combination of physical features significantly different from adjacent areas. Changes from one site to another represent significant differences in potential forage production and/or differences in management requirements for proper range use. Range sites are caused by soil, topographical and/or exposure differences. Man-made structures can also alter the natural environment and create artificial sites.

Books about soils are available and there is no need to dwell on this subject in detail. Soil structure is an important factor causing site differences. Structure is a dispersed system made up of particles of varying size: gravel, coarse sand, fine sand, silt and clay. The proportion of these plus other features determines the production potential of a soil. As a general rule, water infiltration rates increase and water holding capacities decrease with increased sand content. Mineral contents cause significant differences in potential plant production. Deficiencies or excessive amounts, such as salt, affect both forage quantity and quality. Range sites and pedological classifications do not always coincide. Two different kinds of soils adjacent to each other may produce the same kind of vegetation.

Soil depth is a major factor causing sites. Potential declines with soil shallowness. High forage production requires large root systems and shallow soils do not have adequate space for the development of such systems. Topography also influences productivity. In general, productivity and degree of slope are inversely related. The best use of most steep slopes is no use because their watershed values are greater than their forage values. Valleys can produce more than would be expected with an average annual rainfall because of their deep soils and because they receive additional water from surface runoff. Man-made structures can also alter potential.

Sites should be named according to their physical features, not according to vegetation types. Vegetation can change, physical features cannot. While this point might seem trivial, some serious misinterpretations have been made with site delineations made on vegetation types. Poor condition ranges, for example, have been considered as being the potential. Some site names that appear frequently in land capability surveys are wetland, subirrigated, coarse sands, ordinary uplands, valley, steep rocky slopes, shallow uplands, gravel, saline overflow, saline uplands, very shallow uplands, gradual slopes, etc.

Table 7 illustrates the differences in forage production as related to range sites and range condition on Texas' Fort Worth Prairie. The valley site in excellent condition produced two times more forage than poor condition on the same site. Poor condition on the valley site produced almost exactly as much forage as excellent on the ordinary upland and more than excellent on the slopes. From another point of view, it takes 2.5 ha of slopes or 1.7 ha of ordinary upland in excellent condition to produce as much forage as 1 ha of valley in the same condition.

Figure 13. General characteristics of range condition classes in a semiarid area (Adapted from SCS, USDA).

Table 7. Kilograms of dry forage production per hectare as related to range sites and condition on the Fort Worth Prairie, Texas. (Adapted from SCS, USDA)

Further analysis of the data in Table 7 shows that the poor condition on the valley site produced about one-half as much forage as excellent, whereas poor condition on the other two sites produced around one-third as much as excellent. Range condition in this case was determined by the decreaser, increaser and invader method previously described. With this method, a species can be an invader on one site, an increaser on another site or a decreaser on yet another one, all being in close proximity to each other. A poor condition range on some sites may be poor ecologically, but not so poor from forage production and environmental protection points of view. Lacking expertise in range condition determination methods, the public can be misled by popular articles about the status of rangelands.

González (1966) reported similar relationships as those in Table 7 for the various kinds of rangelands in the state of Chihuahua, Mexico. These are illustrated in Figure 14. There were considerable differences in forage production between the vegetation types, regardless of condition. The potential for the halophytes and shrublands is very low compared to the grasslands. Excellent condition on the various kinds of rangelands produced much more forage than the other condition classes making the attainment of excellent condition a worthy goal. There was considerable variation in production due to sites.

Range condition and sites as related to grazing capacity and animal production

FAO's study entitled "Agriculture: Toward 2000," which pertains to long-term global development up to the year 2000 for the countries and regions of the world, considered two alternatives: (1) continuation of past trends (1961-65 to 1979) in agricultural growth and development and (2) normative targets for accelerated general and agricultural growth. The latter analysis does not pertain to potential growth as it is based on what would be expected to happen with a gradual upgrading of the utilization of resources through appropriate technologies. The results of this study regarding beef production in the Region are presented in Table 8.

Figure 14. Forage production as related to range sites and conditions within various vegetation types in Chihuahua, Mexico (Gonzalez, 1966)

Table 8. Beef balance projections between production and demand for Latin America and the Caribbean up to the year 2000

Thousands of metric tons

1. Continuation of past trends (1961-1979).
2. Accelerated growth with a gradual and possible upgrading of the utilization of resources through appropriate technologies.

It was predicted that if past trends continue, the Region as a whole would have a deficit in respect to demand in 1985 and that the deficit would increase several fold by 2000. This deficit will be particularly serious in the Caribbean, Andean and northeastern Atlantic sub-regions of which many countries are already importers of beef. However, Mexico and Central America, according to the analysis, will not be in deficit until 2000 and the southern countries will still have some surpluses at that time, enabling them to remain in the international trade of beef.

The situation is somewhat brighter for the Region as a whole, but not for some sub-regions, when analyzed from the normative target point of view. The Caribbean and Andean countries are still predicted to have considerable deficits, but the other sub-regions and the Region as a whole will have some surplus up to and beyond the year 2000.

Similar trends are expected regarding mutton, but the predicted future regarding milk supplies can only be considered as bad. All sub-regions are predicted to have a high milk deficit by 2000 even if the normative targets should be met. The predicted deficit by 2000 for the Region is 14.4 million tons if historical trends continue and 6.0 million tons if normative targets are met.

There is no reason to believe that the projected levels of production under the normative analysis cannot be met in some countries, but it will take a greater effort than in the past on the part of all concerned: planners and policy makers, scientists, technicians and producers. Moreover, a passive attitude cannot be taken in that meat and milk deficits can be filled with food crops because deficits are predicted for many of these as well. Therefore, the Region must take full advantage of its livestock producing resources in order to meet the challenge that it is faced with.

The greatest potential for increasing beef production lies with the improvement of reproductive efficiency and annual extraction rates, reduction of death losses and increased grazing capacities. A 1975 FAO study in Chile, Peru, Venezuela, Argentina, Brazil and Colombia showed that grazing pressures on both native and artificial pastures were close to or exceeding grazing capacity and that little progress could be made in future through a simple increase in livestock numbers which would likely decrease production rather than increase it. It was calculated that with an average extraction rate of 12% the total cattle population for these countries would produce around 19 million head for slaughter. Increasing extraction rates through improved management by 1% each year, while maintaining herd numbers equal, would give an increase of 1,654,000 head for slaughter per year and an eventual extraction rate of 18% would yield 9,927,000 more head for slaughter.

Individual animal productivity is related to degree of utilization as shown in Figure 8. However, since this is such an important subject in respect to both livestock production and desertification control, it will be re-emphasized in greater detail in a later subject. The focus here is on the determination of grazing capacity and to illustrate how livestock numbers can be increased without damage to the environment, resulting in increased food production to help meet the ever increasing demand.

It is interesting that there are very few studies regarding the influence of range conditions per se on individual animal performance. The consultant conducted such a study several years ago on twenty ranches in Kerr County, Texas, USA. All ranchers kept records, many do not, and all ranches were grazed with a combination of cattle, sheep and Angora goats. The ranches were divided into those with high poor to fair condition ranges and those with good condition ranges. The average stocking for all ranches was 7.3 ha per animal unit. It was estimated that the degree of use for the poor to fair condition ranges was approaching proper, some being slightly over. The degree of use for the good condition ranges was proper, some being slightly under. While these degrees of use could have influenced animal performance, it was felt that this was not a major contributing factor. All ranchers had good and well managed stock.

The results are given in Table 9. Except for kid hair production, individual performance was better for all the livestock grazing the good range than those grazing poor and fair. There was a much higher percent increase with cattle than with sheep and goats. Since cattle prefer grasses to fortes and browse, this was attributed to a greater abundance of desirable grasses on the good condition ranges than on the poor to fair ones. An increase in sheep production, especially lamb weaning weight was satisfactory. While grown mohair yields increased considerably, kid hair decreased for no apparent reason. It could have been related to age at time of shearing.

Table 9. Average individual animal performance as related to range condition on twenty ranches in Kerr County, Texas (Hues, Unpublished Data)

These data indicate that ranges in good and excellent condition have a better yearlong supply of palatable and nutritious forage than do ranges in poor and fair condition. Livestock respond accordingly. Improved range condition nearly always improves the habitat for wildlife. This is assured by good range management which leaves adequate protective cover. The myth that domestic livestock grazing causes a decline in wild animal numbers is not true in the face of good management.

For example, the 1923 big game populations in the state of Wyoming, USA, which has 50% public lands, most of which allow livestock grazing were: 22,000 elk, 20,000 deer and 13,000 antelope. In 1990, these were: 68,000 elk, 517,000 deer and 344,000 antelope (Anonymous, 1993). Range management was not even born in 1923, and the relatively low wildlife populations were probably due to rangeland abuse. There has been an astounding wildlife increase since that time, a large part of which can be attributed to livestockmen working hand in hand with technicians regarding better use of the range resources. The case of Texas Edwards Plateau as previously described under the section "Continual Destructive Grazing" is another example of livestock and wildlife living together harmoniously.

Grazing capacity cannot be determined easily. Many factors are involved such as weather fluctuations, seasonal variations in forage production and palatability, forage or site accessibility, variations in livestock preferences and many others. Regardless, estimations can be made based on either experience, research results, interpretations and/or certain methodologies. A logical estimation puts one in the "ball park." Once in the ball park, the accuracy of the stocking rate in accordance with the estimated capacity can be monitored with degree of use and range condition trend measures and even livestock performance. These would dictate needed, if any, changes. Range condition and site determinations are essential to grazing capacity estimations.

Grazing capacities are expressed as area per animal unit. An animal unit (abbreviated as A.U.) is one mature reproducing cow with or without calf, or its equivalent. Conversion factors are: cow, 1.0; mature bull, 1.25; weaned calf, 0.6; yearling 12 to 17 months of age, 0.7; yearling 17 to 22 months, 0.75; two-year-old from 22 to 32 months, 0.9; white-tail deer, 0.14; mule deer, 0.2; elk, 0.7; mature ewe, 0.2; ram, 0.2; weaned wether, 0.17; doe goat, 0.17; buck, 0.17; weaned wether, 0.14 and mature horse, 1.25. Capacity can be expressed as area per A.U. per year such as 6 ha/AU/year or as area per A.U. per month (A.U.M.) such as 0.5 ha/A.U./month. The former is usually expressed simply as ha/A.U.. The latter is used with seasonal grazing.

Once the average productivities for the various range conditions on the involved sites are measured, stocking rate guides can be calculated. An A.U. is allotted around 5,000 kg of air-dry forage per year. It might not consume this amount, but it tramples a lot and it is competing with microconsumers. The recommended stocking rate is calculated as follows:

5.000 Kg. of Forage/A.U.
Ha/A.U. = Production/ha x 0.5

Why multiply forage production by 0.5? Because 50% should be left for proper nutrition of the plants. Remember, "take half leave half" is the general rule.

It was shown in Table 7 that the average air dry forage production for a range in excellent condition on an ordinary upland site is 3,090/ha. Using the above formula the estimated grazing capacity would be:

Ha/A.U. = 5.000/3,090 x 0.5 = 3.2 ha/A.U./year

For poor condition, it would be:

Ha/A.U. =5.000/1,030 x 0.5 = 9.7 Ha/A.U./Year

Stocking rate guides can be made with adequate information. Table 10 is an example made from the information in Table 7. There is a range in the recommended stocking rates to allow for variations within condition classes such as very poor, poor, high poor, low fair, high fair, etc. The range is wider for poor and fair than for good and excellent because there is greater variation among them.

Grazing capacity determinations for a specific production unit, private ranch or community grazing area, requires consideration of other factors beside range sites and conditions such as grazing distribution, accessibility and feasibility. A hypothetical example of how all of this could apply to a 5,800 ha ranch is given in Table 11. Only 4,300 ha are grazeable and the grazing capacity is based on the sites and conditions within these 4,300 ha and not the total 5,800 ha. There are many real situations similar to this, clearly showing that all land is not equal. The total recommended stocking rate for the 5,800 ha ranch is 190 A.U.s.

Table 10. An example of a stocking rate guide based on the information in Table 7

Table 11. Hypothetical grazing capacity situation on a 5,800 ha ranch

1. Very erodible, grazing not recommended.

In conclusion, it is obvious that livestock and wildlife numbers can be safely increased and desertification controlled with improvement in range condition. Beautiful spinoffs are more animal products and stabilized range environments. Going back to the ecosystem, the manipulator can use livestock to achieve this. Many methods are available to him or her, needing only implementation.

Range Condition and Sites - the Planner's Tools

Range condition and site analyses and interpretations can be most useful to planners. A dominance of poor condition range is proof that past management was improper. Reconstruction of past management provides valuable information as to what should be avoided, both currently and in future. Stocking rate histories provide information for the formulation of stocking rate guides. The kinds of livestock grazed in past helps to explain the current vegetation status and provides clues regarding changes that might be needed.

The species composition helps to identify managerial needs and practices to be applied. Should the range be grazed only by cattle or sheep or goats or by a combination of these? Is there an adequate amount of desirable and less desirable species for secondary succession? If not, reseeding should be planned as well as the most feasible method. Will secondary succession be retarded or held in check by brush and weed competition? If so, brush and weed control should be planned as well as the method or methods. Is some sort of rotation or deferred rotation grazing system needed to either maintain current composition or enhance succession? This might not be the case with good and excellent ranges and proper yearlong grazing would be sufficient. This is nearly always the case with poor and fair condition ranges and the planner must design an appropriate system.

If there is a grazing distribution problem as shown in Table 11, the analyses will reveal it. Note in Table 11 that sites 2 and 3 are in poor condition, site 1 is in both fair and good condition and site 4 is excellent. This indicates poor grazing distribution. The planner must determine why, and devise solutions. The above are just a few examples of why range condition and site surveys serve as the planner's or the manipulator's tools. There are many more examples. But, above all, the planner must estimate the grazing capacity and convince the livestockman to stock accordingly. This will likely be the planner's most difficult task.