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Knowledge of carbon dioxide concentration in desert soils is required in theoretical models of the development of pedogenic and ground-water calcium carbonate. Most studies have concentrated on medium- to fine-textured soils in temperature to humid environments. Very little data exist for CO2 concentrations in stony, coarse-textured deposits such as those making up alluvial fans and fluvial terraces. The purpose of this study was to obtain CO2 concentration data in stony, coarse-textured, uncultivated soils in a desert environment.

Soil gas samples were collected from two sites - Yucca Wash and Rock Valley - at the Nevada Test Site in southern Nevada between June 1985 and June 1986 to determine soil CO2 concentrations and their seasonal and depth variations in the soil profile. Soil CO2 concentrations ranged from 0.03 volume percent in winter and summer to 0.25 volume percent in spring. During the summer, fall, and winter, CO2 concentrations were close to atmospheric levels and varied randomly with depth. In spring, CO2 varied with root density, highest concentrations occurring between 40 and 80 cm of depth. Maximum CO2 values decrease and occur at progressively deeper levels toward the end of spring. Biological activity appears to be limited throughout the year because of the arid climate. During the winter and spring, soil CO2 appears to be more dependent on temperature than moisture, whereas in the summer and fall it appears to be dependent on moisture.

Soil gas samples were also collected during the spring from three sites in the Kyle Canyon area in southern Nevada to determine the variation of soil CO2 levels with changes in elevation and vegetation. Soil CO2 values increased from 0.04 to 0.24 volume percent with increasing elevation. The increased elevation is associated with increasing precipitation, greater vegetation increasing precipitation, greater vegetation density, and decreasing temperature. The CO2 values at the mid-elevation of 1400 m in Kyle Canyon were similar to CO2 values at Yucca Wash at 1266 m in elevation for the spring of 1986.