ABSTRACT
Facilitation affects plant community structure and diversity in very different ways than competition. Traditional models for plant interactions have emphasized competition, assuming that plants must compete for always-limiting resources, such as water, nutrients, light, space, or pollinators, and try to overthrow each other when in proximity. Marrubium plants under Retama had greater leaf-specific area, leaf mass, shoot mass, leaf area, flowers, higher leaf nitrogen concentration, and more nitrogen per plant than those that were not near a Retama shrub. Experimental studies of the relationship between soil enrichment via litterfall and enhanced growth of plants or species shifts are less common. Plants that are highly attractive to pollinators may facilitate their less-attractive neighbors by enticing insects into the vicinity. Patterns of nurse plant mortality observed in numerous systems indicate that species may begin their lives as the beneficiaries of nurse plants and later become significant competitors with their former benefactors as they mature.
