Manipulation

MANAGEMENT OF RANGELAND ECOSYSTEMS THROUGH MANIPULATION CHANGES
IN THE ORIGINAL NATIVE SYSTEM

-by C. Wayne Cook

In spite of common belief, the natural ecosystem is not always the most efficient in the conversion of solar radiant energy in primary production or the transfer of energy in secondary production. A manipulated system may produce more dry weight of plant material and frequently furnishes a diet more conducive to meeting nutritional requirements of the consumers than the native ecosystem.

Ecosystem Conversion

Transformation of the ecosystem may involve complete conversion of one vegetation type to another by cultivation and seeding. Partial conversion of the ecosystem might be accomplished by burning, by the use of herbicides, or by railing or chaining. As shown in Table 1, the quantity of converted solar energy that can be transferred to livestock may be increased many times under some form of conversion. The efficiency of energy turnover can further be enhanced if the seeded forage more nearly meets the nutritional requirements of the grazing animal.

Table 1. Total usable energy produced per acre for native range and seeded range.
	Native Range	Seeded Range
Production of usable forage (lbs/A)	180	952
Degree of utilization per cent (controlled)	50	50
Pounds consumed per acre	90	476
Gross energy eaten (kcal/A)	171,000	1,047,000
Digestible energy eaten (kcal/A)	90,000	571,200
Metabolizable energy eaten (kcal/A)	63,000	428,400

Before successful seeding of ranges can be carried out, research must show which sites are suitable for seeding, how best to prepare the seedbed, what species to seed, what season and method to seed, rate of seeding, spacing of seeded rows, and what method of grazing management produces the greatest net economic return over the longest period of time.

The inadequacy of seasonal ranges for yearlong grazing is perhaps the most limiting factor in livestock production in most parts of the world. Research by Cook indicates that about 80 pounds more beef per calf and 30 pounds more lamb weight per ewe can be obtained by using improved range for lambing and calving.

Man should recognize the efficiency of natural selection of plant species over time, but he must also investigate the desirability and suitability of introduced plant species or newly developed varieties. It has been shown that man can improve upon nature in many ways for increased efficiency of the native ecosystems. Natural selection over geological time has been serving an entirely different purpose. Man's intelligence and perseverance will find even newer means of increasing the productive efficiency of the rangeland ecosystems. This may be far beyond our present expectations, but to be sure, it can far exceed the natural output of our present rangeland ecosystems.

Reseeding or Interseeding the Natural Rangeland
Ecosystems for Special Uses

Most any western plant expression presently on level or moderately level rangeland, that will allow modern farm machinery to operate, can be tilled to eliminate the present plant stands and permit reseeding to new or different species. This procedure can increase the available forage from 2 to 10 times its present yield. This is a reasonable statement because all plant life on even protected or little used rangeland, that do indeed resemble virgin rangeland, can produce more forage in a selected species mixture included in a reseeding plan on most tillable western rangelands.

Potential reseeded land is classed above desert rangelands. However, meadow land used for haying purposes has not always been improved under reseeding conditions. Common reseeding projects include only a single species of forage to meet a single season's needs such as early spring grazing for early lactation needs. Late summer and fall grazing presents a crucial need for late lactation and weaning and is presently being met by use of "seeded grazing-sorghums."

Likewise we need to increase the protein and mineral (phosphorus) content in the diet for fall and winter grazing on most native grassland ranges of the Northern Great Plains. This can be accomplished by inter-seeding 4-wing-saltbush (Atriplex canescens) directly into the native grassland range in small acreages here and there, or seeded in contour furrows here and there in the range.

Controlling Undesirable Plant Species
in the Rangeland Ecosystems

Controlling unpalatable brush and weeds on rangelands by means of selective herbicides offers great promise. In the future, it may be possible to control most any single undesirable species without harming any of the others in the flora. There are presently over 3000 identified selective herbicides but only a few hundred have been tested and fewer than fifty are currently in use on rangelands. At present, over three-fourths of our poisonous plants can be effectively controlled by selective herbicides.

Research on rangelands of the western United States has shown that controlling undesirable brush species in seeded and native stands of foothill grass increases the forage yield by as much as 1200 pounds of forage per acre, and control of dense stands of unpalatable forbs on mountain ranges increases the forage as much as 800 pounds per acre. Control of annual weeds and annual grass by selective herbicides prior to seeding and during seedling establishment has made it possible to obtain grass stands where before it was impossible because of weedy competition.

Benefits from Applying Fertilizers to Rangelands

Recently it has been found that the addition of fertilizers on native rangelands has increased the herbage yield many fold. Research in range fertilization should be concerned with evaluation of the following expected benefits: 1) increased forage yield, 2) increased nutrient yield, 3) increased vigor of plants, 4) increased palatability, and 5) improved distribution of livestock on rough mountain topography.

Fertilizing seeded foothill range in the western United States has shown that as much as 800 pounds of additional forage per acre per year can be obtained when 40 pounds of nitrogen per acre are applied every year. On mountain meadow ranges as much as 1440 pounds of additional forage were obtained when 60 pounds of nitrogen per acre were applied at the beginning of a 3-year period (Table 2). Protein content was increased by one-third through the application of the nitrogen, and as much as 300 to 1200 pounds of additional digestible nutrients per acre were produced on seeded foothill and mountain meadow range respectively. Other benefits derived from fertilizer were increased palatability and increased vigor of plants.

Table 2. Average yield of energy per acre over a 3-year period from adding 60 pounds of nitrogen during only the first year.
	Native Range
	Unfertilized	Fertilized
Production of forage lb/A	620	2,060
Degree of utilization per cent (controlled)	50	50
Pounds consumed per acre	310	1,030
Gross energy eaten kcal/A	651,000	2,523,500
Digestible energy eaten kcal/A	352,510	1,413,160
Metabolizable energy eaten kcal/A	251,410	1,059,870

Fertilization of rangelands has not generally been practiced by ranchers because of the high cost of fertilizers. However, research by range scientists have in various parts of the western United States found that the benefits justify the high cost of range fertilization on most range areas not classed as deserts.

Mechanical Land Treatments

Contour furrowing, pitting, and water spreading have all contributed to improved moisture absorption and increased forage yield on many rangeland areas in western North America where precipitation is sparse and soil moisture is limiting.

In many arid rangeland areas where vegetation is sparse and torrential showers are frequent, effective soil moisture can be increased many fold by land treatments that hold the moisture on the soil and allow it to recharge the soil mantle by water spreading techniques that are currently available and widely used at the present time.

Control of Plant Diseases

Additional research concerning the effect of plant diseases on primary productivity needs to be carried out on natural ecosystems. Fungi, bacteria, viruses, and nematodes are representative groups of pathogens that attack range plants and reduce productivity and quality of herbage. It is known that these pathogens are ever-present but they almost never reach catastrophic proportions. As a result, plant pathologists have not completely identified these diseases or comprehensively assessed their effects upon range plant welfare.

Control of Rangeland Insects

Frequently, invertebrates become so numerous that the competitive effect with livestock threatens the stability of the livestock enterprise. Among this group are: grasshoppers, crickets, army worms, tent caterpillars, harvester ants, termites, snout moths, and many other species of moth larvae and beetles. It is well known that many insects change the species composition of the vegetation completely; yet as managers we generally tolerate the consequences. The rationale for this is known as ‘peaks in population dynamics': by ignoring the problem it will disappear over time through a normal decrease in population numbers.

Control of Small Mammals

Perhaps the most notable examples of damage to the range resource from rodents come from Australia and New Zealand. In all parts of the world, peaks in rodent or lagomorph populations have caused serious competition with range livestock. In America, competition exists from such small mammals as the rabbit (Lepus spp.), prairie dog (Cynomys spp.), kangaroo rats (Dipodomys spp.), ground squirrels (Citellus spp.), pocket gopher (Thomomys spp.), and field mice (Microtus spp.).

In most cases, control methods have not been successful. The use of poison baits has been the method most widely used to control rodents. Generally, control methods have merely reduced numbers of animals to a point that allowed increased rate of forage productivity by the animal treated. Therefore, the relief may be only temporary. The reduction would have perhaps occurred eventually as a normal expression of population dynamics. Knowledge of the behavioral patterns and the dietary habits of all small mammals is beneficial in the management of the ecosystem.

MANAGEMENT OTHER THAN
ECOSYSTEM MANIPULATION

Rangeland management is more than manipulating the ecosystem for increased quantity and quality of forage. It involves identifying all factors that may be limiting to the function of the ecosystem for optimum productivity.

Identification and evaluation of limiting factors in the ecosystem involve all of the complicated interactions related to the climatic, edaphic, and biotic factors. Management decisions are based primarily upon the knowledge of these factors and their interactions. These include plant-x-plant interactions with climate and soil nutrients, such as plant survival during extreme drought along with high temperatures and with or without adequate soil nutrients.

Interactions of paramount importance to management involve plant, animal, and environmental factors. Actually, proper management of the grazing ecosystem is a reflection of climate and plant and animal interactions.

Season and Intensity of Grazing

Research in the western United States shows that desert ranges have more than twice the carrying capacity when used only during the winter compared with use during the spring or summer. The condition of the range greatly influences carrying capacity. Desert ranges in poor condition can support only about one-third the numbers of livestock that can be grazed safely on comparable ranges judged to be in good condition. In the Intermountain area of the western United States, most foothill and mountain ranges in poor condition produce only about one-fifth as much forage as good ranges.

Intensity of grazing profoundly influences the daily intake of forage and the nutrient content of the consumed material. Heavy grazing has been found to decrease daily forge intake by one-third and reduce the digestibility of all nutrients in the diet. This is the result of animals being forced to consume more coarse plant material.

Livestock Distribution

Poor distribution of cattle on rangelands, especially mountainous ranges because of poor salting practices, undeveloped watering facilities, and insufficient herding of animals away from normal areas of concentration has, in many cases reduced the grazing capacity by as much as 60 percent. Studies indicate that good salting practices can increase cattle production on a range by as much as 30 percent. Water development on several mountainous experimental ranges has increased the capacity by as much as 50 to 100 cow months per development. Driving cattle every week or twice a week from areas where they normally congregate can aid immeasurably in fostering better distribution and range utilization. Trail construction through rocks, down timber, and thick brush that hinder livestock travel, offers tremendous possibilities for increasing carrying capacity of the range.

CLIMATE AND MANAGEMENT OF THE ECOSYSTEM

Influence of the vagaries of weather on the function of the ecosystem presents a most formidable problem to range management. Rangeland ecosystems are characteristically located in arid zones throughout the world. The average annual precipitation on native grazing lands of the world lies between about 6 and 20 inches and these areas are subject to intermittent and severe droughts. The effectiveness of the precipitation depends upon top soil depth and climatic factors including temperatures, humidity, and wind storms of destructive velocity, all of which affect evaporation and transpiration.

In rangeland ecosystems it is not uncommon for precipitation to be well below normal during any year or even a series of years. In many localities of the rangeland area of the United States, native vegetation has undergone serious degradation during drought years, even though grazing was conservative or completely absent. The effects are so profound that recovery sometimes requires from five to fifteen years.

In many range areas it has been found that forage production is highly correlated with seasonal distribution of precipitation during a particular period of the year. In some cases, this can be used to forecast carrying capacity of the range during subsequent seasons or years.

Studies by Cook showed that some plant species on desert areas could tolerate only light grazing and during drought years little, if any, grazing. In studies on foothill ranges it was found that range deterioration was largely a result of drought (60 percent of normal precipitation) and continuous grazing without allowance for recovery following drought. Range deterioration took place during drought years even when grazing was considered conservative (25 to 50 percent of current year's growth).

Certainly the stability of the range livestock enterprise depends upon the flexibility that can be incorporated into the grazing operations. Generally the more arid the climate the greater the fluctuation in herbage production from year to year. The drier range areas are in a delicate balance and once deterioration takes place, it requires relatively long periods for natural restoration. Ranges located under more favorable climatic conditions respond more rapidly to alleviation of abuse and as a result they require less flexibility in operation than general desert areas.

It has been shown on foothill areas of the western United States that vegetation consisting of annual species may be expected to vary as much as 100 percent from one year to another but perennial vegetation would not be expected to vary more than about 45 to 50 percent.

Flexibility in stocking range areas of the western United States is employed mainly through conservative grazing and the sale of inferior animals during dry years. Some livestock operations have ranches in two or more areas so that animals can be moved from one to another when drought is severe.

PLANT RESPONSES - A KEY TO MANAGEMENT

It is recognized that biological efficiency of the ecosystem is measured by responses of both plants and animals to management. However, once the nutritional requirements of the grazing animal have been provided by various vegetation types, management becomes largely a matter of plant welfare.

Physiological Responses of Plants to Defoliation

The question arises, should the management system allow for a minimum of photosynthetic tissue at all times to optimize the conversion of radiant energy or is it more beneficial to graze rather harshly and obtain more uniform use of the range and allow the plants to regain vigor through deferred-rotation or rest-rotation grazing? Leaves, as they mature, become less effective in their capacity to carry on photosynthesis. Therefore, grazing methods that provide for the removal of apical buds and primordia so that new leaves are formed from stimulated latent or crown buds will generally increase the quality of primary production.

Since grazing prevents the transition from vegetative to reproductive material and since vegetative growth is more nutritious, it is readily understood that secondary productivity of the ecosystem is benefited by grazing during the growing period.

Can the cycle of carbohydrate usage and storage be used as an index to proper season and intensity of grazing? Are plants that draw down on the carbohydrate reserve rather rapidly during initial growth more susceptible to early or heavy use than plants that grow more slowly and draw upon the carbohydrate reserve rather conservatively? Is a plant species that replenishes its reserve rather slowly after initial draw down during early growth more susceptible to continued season-long use than one that replenishes its reserve rather rapidly after initial draw down? To a degree, these questions are related to the growing conditions following defoliation and the ability of the plant to replace its leaf area rapidly.

Ecological Responses of Plants to Grazing

A modern concept of ecosystem management is related to the ecological principle of succession and regression toward and away from the peak expression or what we recognize as a desirable expression of plants and soils in a stable condition. Criteria for identifying the general health or condition of the range with effective criterion for identifying range condition (good, fair, or poor) can be accomplished primarily by the percent cover composed of desirable plants, based upon their natural expression in the complete floristic mix.

The stability of the range is referred to as a trend in range condition. If the range is deteriorating or changing in the direction of retrogression, it is said to be in a downward trend. If, however, there are signs of plant succession toward a desirable expression, the range is in an upward trend. It is reasonable to assume that any range condition (good, fair, or poor) can be managed in a rather stable condition. This is reasonable because the theory of natural succession must accept that stabilizing conditions for both soil and plant development exist throughout the various waves of plant expression during serial development in order to arrive ultimately at an acceptable expression.

Ecosystem management is based upon the ability of range managers to identify range condition and detect the trend. This is not easy for the inexperienced range technician because objective measures or quantitative criteria are complex. The basic principles involve the ability of the appraiser to detect changes in species composition of the plant cover. In theory, this concerns a change in the occupancy of the perennial species that require an opening of the community for entry. When range conditions are moving downward there will be a lowering of vigor of the more palatable species, but a range condition that is improving does not necessarily show lowered vigor of the secondary species to be replaced over time by the primary species.

It is generally acknowledged that seed production is necessary if desirable species are to reclaim deteriorated range areas. Seed production, however, may not be required in closed communities judged to be in satisfactory condition, because regeneration through seedlings in a closed community is necessary only to the extent of replacing decadent plants.

It is recognized that soil development and soil deterioration are of paramount importance in judging range condition and trend but quantitative information does not allow for absolutely accurate identification for either situation. It may be that certain hydrological characteristics may be more easily measured and understood than the estimated degree of accelerated soil erosion or actual extent of soil erosion taking place under the present condition.

RESOURCE ALLOCATION

Rangeland is all land producing native forage for animal consumption and land that is revegetated artificially that is managed like native vegetation. Rangeland represents a renewable natural resource (plants) that can be harvested annually by grazing animals on a sustained yield basis.

Range management deals with the care and use of rangelands in meeting the current and long-term needs of ranchers, sportsmen, recreationists, water users, foresters, and the meat-eating public in general. Scientific range management stands on the premise that the range resources can be managed at a stable state for grazing livestock and wild game, while at the same time producing high-quality watersheds and outdoor recreation.

Therefore, if directed manipulation in the ecosystem is to be made, it should be with the intent of minimizing any adverse effect on other uses.

Allocation of multiple use of rangelands will require:

1) establishment of criteria for evaluating suitability of the ecosystem for each use;

2) appraisal of the demand or need for each use; and,

3) decision-making models for allocation of resource uses.