Contribution of Shrubs to the Nitrogen Economy of a Desert‐Wash Plant Community

Total nitrogen incorporated in the shrubs of a low—fertility desert plant community (principally Acacia Gregii, Cassia armata, and Larrea divaricata) was estimated from the nitrogen content of plant parts, the total weight of plants and proportional weight of roots, stems, and leaves, and the number of plants per unit area. The average nitrogen content of shrub leaves, stems, and roots was 1.31%, .87%, and .80%, respectively. Shrub cover occupied 20% of the ground surface and contained an average of 29 kg nitrogen/ha. Legume shrubs were not significantly greater in nitrogen content than nonlegume shrubs. Soil nitrogen content decreased significantly as a function of radial distance from the center of the shrub canopy. Areas between shrubs averaged 0.19% nitrogen in the surface inch of soil. Soil nitrogen content decreased significantly from the surface to 90—cm depth and was closely related to shrub species and their root—distribution patterns.