Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Wildland Resources

Department name when degree awarded

Range Management

Committee Chair(s)

L. A. Stoddart


L. A. Stoddart


C. Wayne Cook


The reciprocal effects of vegetation and soils have long been a subject of speculation and conjecture. In the management of any natural land area the problem of interpreting vegetational expression is especially important. The effects of native vegetation on soils and the effects of the soil on the vegetation have been studied and observed for many years. The arid-desert range lands have been studied least and as a result are not well understood.

As human populations increase there will be additional need for agricultural production, and these lands may be put to higher use, perhaps even to irrigated crop production. Basic to increasing the productivity of these lands is an understanding of the vegetation they are now supporting, what they supported prior to their use by domestic livestock, and why the present vegetation grows to the exclusion of other vegetation types.

The areas under study were confined to the shadscale and sagebrush-grass zones of Utah (7). In these zones the desert shrub types form the matrix of climax vegetation. Embedded in this matrix are what appears to be edaphically controlled climax communities.

Grazing in the past 60 to 70 years is believed responsible for considerable change in floristic cover on the salt-desert. Some perennial herbaceous species belonging to the climax have decreased or over extensive areas perhaps disappeared. Some of the more desirable shrubs also have been reduced by grazing. In many cases annual herbs have become established in vacated areas. The result of these changes in floristic composition is a less desirable forage and consequently a decline in grazing capacity.

The invasion of halogeton (Halogeton glomeratus) on abused range lands of the intermountain west has done much to bring the retrogradation of these ranges to public attention. Hundreds of thousands of dollars have already been spent for study and control of this plant. Money is still being appropriated for these purposes.

Native vegetation in a vigorous state of productivity apparently controls local invasion or suppresses extensive occupation by halogeton. Most attempts at seeding arid salt-desert ranges have been unsuccessful, therefore, a knowledge of vegetation composition obtainable under good management is of primary importance in land administration. Most problems of range deterioration must be answered through natural rehabilitation and wise use of natural forage species.

Classification of these range lands is an important function of the administering agencies. Proper carrying capacities and management practices should be based on correct classification of the lands. In order to appraise present condition of these range lands the normal condition or climax must be understood. The Bureau of Land Management which controls most of this salt-desert land must classify it as to whether it is potentially arable or not. The question arises as to whether vegetation now present on these salt-desert ranges is an adequate index to their capabilities.

Plant indicators have been used to a limited extent for classifying areas for cultivated crop production and for grazing. The role of ecotypic variation within the plant species has been largely overlooked in classifying salt-desert lands. Essential to use of plant indicators is knowledge of whether these dominant species require some particular element or condition found in the soil or whether they are present merely because they can tolerate these conditions. This knowledge is vital to an understanding of the distribution of the flora and to the successful management of the salt-desert ranges.

This study was initiated to obtain information contributing to a better understanding of why some of the desert plants grow where they do, and what role soil, water, and minerals play in plant distribution. Such information should be a useful tool in the hands of persons attempting to classify these lands properly.



Included in

Life Sciences Commons