Date of Award:

5-1978

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

John J. Skujins

Committee

John J. Skujins

Committee

Neil E. West

Committee

Fred J. Post

Abstract

Soils from four regional deserts, Great Basin, Sonoran, Chihuahuan, and Mojave, were collected at times throughout the year which would best exhibit microbial response to moisture or vegetation. The soils were analyzed for several chemical and physical properties. Biological and biochemical characteristics, namely respiration, dehydrogenase activity, adenosine triphosphate concentration, proteolytic activity, nitrification potential, and microbial numbers, were measured.

The soils exhibited fluctuations in microbial activity as measured by respiration, dehydrogenase activity, adenosine triphosphate concentration, proteolytic activity, and nitrification potential during different moisture seasons.

Increase in soil moisture as modified by precipitation did not cause a significant difference in respiration or proteolysis between desert soils, however, an increase in moisture did cause a significant difference in nitrification potential of desert soils. Proteolytic activity was highest in soils collected when above-ground portions of desert plants were dormant.

Low nitrification potential of desert soils was found. Nitrite accumulation in perfusion experiments but not in the field was observed.

Respiration, dehydrogenase activity and adenosine triphosphate concentration did not respond proportionally in desert soils adjusted to different moisture levels. These results suggest that respiration, dehydrogenase activity and ATP concentration each appear to represent a different phase of microbial metabolism in desert soils.

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