Seasonal Water Potential Changes in Sonoran Desert Shrubs in Relation to Topography

Water potential in Sonoran Desert shrubs was recorded from September 1968 through September 1969. Special attention was paid to recording maximum and minimum potentials on a seasonal basis and diurnal fluctuations during the wettest and driest periods of the year. Franseria deltoidea developed the lowest potential (-85 bar) of the shrubs recorded and also showed the greatest degree of response to changes in soil moisture on a seasonal basis and evaporative power of the air on a diurnal basis. Of the species tested, Eriogonum fas- ciculatum showed a high degree of response to changing conditions; Larrea tridentata, Krameria grayi, and Simmondsia chinesis showed a moderate response; and Cercidium microphyllum showed only a slight response to diurnal or seasonal changes.