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An ecological survey of the vegetation of a barrier dune on the south coast of Rhode Island showed Ammophila breviligulata, Solidago sempervirens, Lathyrus japonicus, and Myrica pensylvanica to be the dominant plant species. All plants were mycorrhizal. Six species of vesicular–arbuscular (VA) fungi occurred in association with these plants, with Gigaspora gigantea and Acaulospora scrobiculata the most abundant. Also present were Gigaspora calospora, Glomus etunicatus, Glomus fasciculatus, and an undescribed species of Gigaspora. Spore densities and frequencies were measured in a transect across the dune and were compared with plant cover and physical factors (pH, soil moisture, organic matter, soil nutrients, chlorides, and sand grain size). Areas on the dune with greatest vegetation cover by Ammophila were associated with greatest spore densities and fungal diversity in the rhizosphere. For most plant species, maximum spore density occurred in the front half of the plant's distribution range, nearest the dune crest. There was little correlation between spore populations in the soil and physical characteristics, with the exception of sand grain size. The importance of considering VA mycorrhizae in sand dune stabilization programs is discussed.

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 fasciculatum showed a high degree of response to changing conditions; Larrea tridentata, Krameria gravi, and Simmondsia chinesis showed a moderate response; and Cercidium microphyllum showed only a slight response to diurnal or seasonal changes.

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