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Between shrub and grass communities in coastal California there is a zone that is normally bare of vegetation. Previous studies have emphasized the role of volatile inhibitors of plant growth in producing this bare zone. However, there is a concentration of feeding activity by rodents, rabbits, and birds in this zone; if this activity is prevented by means of wire-mesh exclosures, annuals grow in the bare zone. Thus, animal activity is sufficient to produce the bare zone.
Bruce Bartholomew (Fri,) studied this question.