Geographic Distribution and Factors Affecting the Distribution of Salt Desert Shrubs in the United States

Abstract

Four previously published classifications of intermountain shrub vegetation and a new classification based on maximum salt tolerances and water relationships are presented. Maps show that the geographic range of salt desert shrub species far exceeds the distribution of mappable communities in which these shrubs are dominants. Species differ in their capacity to tolerate soil osmotic stress, but variable results from measurements of osmotic stress in 20 different plant communities indicate that additional factors must be important in determining species present in different habitats. Data obtained by the use of a new method of measuring total soil moisture stress in field samples show that the capacity of different species to remove soil moisture to different maximum stresses appears to determine the kinds of plants that occupy different habitats. Total soil moisture stresses for 14 plant communities sampled ranged from 19 to more than 90 bars.