INTERSPECIFIC PLANT ASSOCIATION EFFECTS ON VESICULAR–ARBUSCULAR MYCORRHIZA OCCURRENCE IN ATRIPLEX CONFERTIFOLIA

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Abstract
SUMMARY: Earlier studies with the shrub Atriplex confertifolia (Chenopodiaceae) suggested that the occurrence of mycotrophy was related to the community from which root samples were obtained; plants in disturbed areas were non‐mycotrophic, while those growing in native areas possessed infection. Upon closer examination when neighbouring plants were studied, the level of mycorrhizal infection of Atriplex confertifolia was found to be related to its interspecific plant associations. When Atriplex confertifolia occurred solitarily, or in the presence of non‐mycorrhizal A. gardneri, it was non‐mycotrophic. However, when occurring near grasses or Artemisia spinescens, it possessed mycorrhiza infection. What appeared to be a community effect for the occurrence of mycorrhiza is nothing more than an association effect in which level of infection is related to the degree of mycorrhizal host plant cover. In disturbed communities little chance occurs for encountering a neighbouring mycorrhizal plant, while native plant communities are composed primarily of mycorrhizal counterparts.